LoneTactix

Airsoft is a weird one. I love it and have since I discovered it 2 years ago but I do sometimes struggle with the whole dress up in full tactical gear and running around like I am saving the world (I do blame the wannabe 'Operators' amongst us for that!). However I then go and play and absolutely love it. I love that moment when you are in the middle of a battle and you take a moment to look around at everyone getting involved and working together (Or not........ See my statement above about the operators!) and I think to myself, this is cool.
 
Deep down we are all a bit nerdy (no offence to anyone triggered by that 🙄). We all have a bit of geek in us. As @Rogerborg states above, the BB does not care where it comes from or where it is going, yet the geek in us wants our 'BB Accelerating Device' to look exactly like a real M4 or AK etc. There is no other reason for this but pure geekyness. Look at the reaction on this forum when ASG released their speedsim version of the M4 with the drop link stock and purple barrels. It does exactly the same as all the other 'BBAD's' but it offended the geek in most of us. Wether we like to admit it or not we all have a bit of geek in us. I own an IT company so I have a double dose of geek and happy to admit it.
 
With this level of geeks comes the collecting, the attention to detail, the need to have the next best thing, the need to know everything we can about what is our current object of desire, etc, etc, etc. At the end of the day we are just a bunch pf happy nerds that like to play dress up and Army. I for one embrace that.

I just bought a shotgun off someone (12/10 would recomend btw) and he sent me a quick wee video of it working and what all the buttons do. guys like that are the real heros of the classfields

Just to give a little data to this thread/topic and to see for myself if there is a significant difference in the behaviour of Bios in wet conditions or a difference between the behaviour of Bios versus Non-Bios, I put a small sample of whatever I had in the house into ziploc bags of water following my last post so these are figures based on the sample BBs being completely submerged in tap water for 18 days (it was night time so I'm counting only whole days).
 
Following the submersion, I measured five BBs from each wet sample and five BBs from the original dry source bottle/bag. I don't have a massive selection and most of those are Bio so I don't have a great control group of non-bio BBs to select from.
 
So, the hypothesis tested is that Biodegradable BBs swell out of spec on absorption of moisture.
 
The attached table is a summary of the results and I think the conclusion I first draw is that there is no absorption or swelling of BBs after nearly 3 weeks underwater.
 
The variation within samples appears greater than that between wet and dry in most cases. Also, I am pretty happy with my standard choice of Nuprol RZR 0.28g Bio 😉
 
There are obvious limitations to the test, primarily in that the sample sizes are small, I can't be fussed expanding the test but I'd be more than happy to applaud anyone who wanted to, I am happy to email the full data table with individual measurements, if anyone is that bored on lockdown. Another possible source of error is the measurement equipment, I used my general garage micrometer to do the measuring, it doesn't have a valid certificate of calibration and it has a stated precision of 0.01mm so the variation seen in most samples falls inside the possible error of the test equipment.
 
Thirdly, this isn't a blind test, I knew what each sample was and so there may be subconscious bias but I doubt it.
 
I really hope this lockdown ends soon, I clearly have too much time on my hands.

Introduction:
I’m making this guide for several reasons, not least because I’m sad and have nothing better to do, or maybe I’m procrastinating from doing real work, but I’d also like to get down on paper some thoughts on the science of our pew pew guns and clear up some misconceptions or at least get a discussion going to better our understanding.
 
This guide is going to be a combination of actual science (well, as close as I can get to actual science ) and some personal experience, I’m by no means the most experienced airsofter out there but I’ve tried over the years to get an understanding of what’s going on and for those new to the hobby this might save some time barking up the wrong tree as I’ve done.
 
Part 1: the goal
Well this is simple, our goal is to shoot some random stranger on a farm on a Sunday and “kill” him, or at least hit him with a plastic pellet and for him to shout “hit” and plod off back to a chequered flag.
 
This sounds pretty easy, but we need to start somewhere, so what do we need to make this happen?
Well we need to hit him for a start, always helps, but not only that but we need to hit him hard. That’s not to say we need to hurt him, but whilst we can argue all day about wether or not people should wear plate carriers the short of it is you need your bb’s to hit with enough energy that he either feels it or hears the impact (which on a field of explosions and other people pew pewing can be difficult).
 
So when our bb hits the target it needs energy.
 
This is why I dislike to some extent the “you can get lots of range from a 328fps gun” argument, yes you can, but how far the bb travels isn’t the only part of getting a kill and just hitting isn't always enough sadly.
 
Part 2: some misconceptions
One thing that I see a lot in various threads is “upgrade your fps it’ll give you more range” or “change to x y or z hop it’ll give you more range” or “use x type of bb it’ll give you more range”, which is both right and wrong depending on how you judge range which will become more clear later.
 
The thing to remember is once your bb leaves your barrel it doesn’t care what happened before, it could have come from a speedsofter’s £3000 hpa or some kids £90 rental ak, it only has 3 things on it’s side to fight the wind/tree branches/gravity to get to the target and these are:
 
Backspin- this gives us our wonderful magnus force that will fight gravity and keep our bb in the air without needing to go at proper bullet speeds Mass- how much the bb weighs Energy- kinetic energy, we often like to use fps as our measurement as it’s how we can best record our performance but what really matters is energy  
So we should probably cover these 3 as they apply to our bb in flight.
 
part 3- backspin
backspin gives us our magnus force, the science behind it is quite interesting and worth a read if you’re interested in expanding your knowledge but in reality the only thing that we need to know is if our hop unit is set right.
 
Now this is different for every setup, how fast the bb is actually spinning doesn’t really matter to us, it could be 1rpm or 10,000 rpm, we don’t care we just want our bb to fly straight.
 
Now personally I set my hop units for a little bit of rise, about 20cm, so that when the bb comes out it’ll rise up by 20cm then start falling back down. The logic here is that if I’m aiming for someone’s chest it’s not going to jump up over their head, miss then drop back down behind them. We’ve all been there where our hop has made us miss someone.
 
In terms of the physics the amount of lift we get depends on 2 things:
The speed of rotation, which is pretty much constant after the bb has left the barrel (well, it slows down a bit but not much) The velocity of the bb  
When we “set” our hop unit what we’re doing is setting the speed of rotation to get the right lift, but if we change ammo or change springs the bb will either be going slower (needing more spin to get the same lift) or faster (needing less spin).
Now the important thing to remember is that if we’re spinning x rpm, then there’s y velocity that gives us the exact amount of lift to fight gravity, but of course a bb doesn’t stay at y velocity, it slows down which is where mass comes in.
 
Part 4- mass
So we have our spin, but as I mentioned bb’s slow down, and this is the misconception I had many years ago that faster bb=more range
The important thing is air resistance, which the faster you go the more of it you have so your bb slows down quicker (moving it out of that sweet spot for the hop spin to work)
 
So say we have a 1j gun, we fire at 328fps on a .2g bb and 270fps for a .3gbb
 
well that .2g bb is going faster, so it has more drag, and it’s lighter so the drag has more effect. The end result is the bb slows down very quickly and it doesn’t take long for it to slow down so much our backspin stops lifting it.
 
Whereas the .3g bb is slower and harder to slow down, sure it might have started out slower but over time it keeps it’s velocity and hence stays in that nice range where the backspin can lift it.
 
So in theory at least a heavier bb spun sufficiently will for the same energy always go further, take a look at the spreadsheet at the bottom and see what I mean.
 
But wait, it gets better!
 
Remember I said we need 2 things to hit a target? Well a heavier bb gives us both!
In the real world we’re shooting through wind and worse leaves, these are forces just like regular ol’ drag and a heavy bb will be blown about less by the wind and has a better chance of punching straight through those pesky leaves and hitting the target, so we get more accuracy, yay!
 
But not only are they more accurate they also carry their energy better, so when we do hit the target at range it’s going to hit it harder, and thus make enough force and noise to let the target know they’ve been hit.
 
So where’s the downside? Why wouldn’t you run sniper .48’s in every gun you own and on every site? Well several reasons:
1.       Cost, damn that pesky real world economics, but obviously heavier bb’s cost more. If you find somewhere selling .48’s for the same price as .2’s then let me know because that’s awesome. Those of us that own support guns with high rates of fire will most likely wince at having to fill it up with costly ammo only to be sprayed into the ether, likewise snipers who don’t shoot much can afford the good stuff hence why they like to run heavy.
 
2.       Travel time, again this is the real world being all awkward and getting in the way of our lovely discussion but remember that our target may not be nice enough to stand still and wait to get hit, especially if he sees our bb’s coming towards him. Heavy bb’s might carry their energy better but they’re slower and take longer to go the same distance, not much longer, but it's enough.
 
edit: it must be noted that a large proportion of perceived travel time is down to the additional range, whilst a .2 will be faster over a short distance remember that a .3 or .4 will still be chugging along long after the .2 as slowed down and dropped.
 
3.       Getting the lift, unfortunately the same properties that make a bb great in flight make them bad for spinning up in the hop unit, and this means that you may find you can’t run them without upgrading your gun and if (like me at the time) you don’t understand fully why it’s happening. This is the “more hop” argument for things like maple leaf/flathop/rhop guns, it isn’t about getting lots of hop on .2’s, it’s about being able to get enough hop on .3’s or heavier.
 
4.       When you don’t need range, now I play mostly outdoors on sites limited to 1j, so for me getting every drop of performance I can is paramount, but say you’re playing in cqb where the maximum distance is maybe 10m, well there’s not much point spending money getting a setup that can shoot well beyond that if you’re not going to be using it, you’d be much better spending money on grenades.
 
So what weight should you run? Well as heavy as you can afford and your gun can lift. Personally I use .3’s for all my “assault” type guns, .2’s in my mg42 (even though it shoots lovely on .3’s) and .43’s in my vsr, although should I ever sell my soul and play indoors I’ll just run .2’s.
 
Part 5- energy
So our final ingredient is energy, most folks will know this as fps because when we’re getting our guns checked at the local site that’s what we get told “oh sorry you’re 400fps and the limit is 350 so you can’t play”.
 
Well what’s really important is energy, kinetic energy, which is a factor of our bb mass and it’s velocity, it’s why the limits are different for different weights of bb’s and why it’s a common tactic of the cheater to rock up at the chrono and say “yeah I’m running .2’s” and to chrono at 328fps while anyone with a lick of sense can hear the smack of the bb’s against the backstop and think “like hell is he running .2’s”
 
This is where I take exception to the argument of “marui’s shoot fine at 328fps, you don’t need fps to get range”, well you do, or at least you should try to get your gun shooting as close to your site limit as you can.
 
The short argument is energy is energy and more is always better, the long version is that energy gives us the velocity that means we need less backspin and can run heavier bb’s without them being really slow and letting our targets stroll out of the path of our righteous pewing.
 
Remember once the bb leaves the barrel it only has 3 things, and mass is the only one it’ll not lose as it flies downrange. As your bb slows down in the wind it loses energy so the more of it you have at the start the better, it’s why all the cheaters want to run hot.
 
A friend of mine recently lent me his m16 to do a bit of work on, he was keeping up in terms of range with most of the folk he was shooting at in part due to a good hop, but he’d rage daily at people not taking hits until we chrono’d it to find it shooting at half the site energy, turned out his floating bb’s were hitting with so little force if he was at any distance people just weren’t feeling it.
 
Now to digress from external ballistics for a second (well, more like 10 minutes) to talk about joule creep.
 
Think about it like this, our bb in the barrel gets pushed by gas, and how long it gets pushed for depends on the length of the barrel and how quickly it’s getting pushed.
 
Joule creep is what happens when you have an “over gassed” gun firing .2’s, whilst you can do this with an aeg or a spring sniper it’s much more common in gas/hpa guns.
 
Think about it like this, your gun can only push so hard, and a light bb will get up to speed very quickly, once it leaves the barrel then it’s not going to be pushed any more. So imagine we had a longer barrel, well if we push just as hard over a longer distance then the bb will spend more time accelerating and hence be going faster.
 
Well the other way to make a bb spend more time in the barrel is to make it accelerate slower, now we can do this by making the bb heavier, so for the same force it’ll accelerate less (remember newton’s f=ma? Who says math class in school was useless). Now it’s not going to come out any faster than the light bb, but it doesn’t need to, it’s heavier so doesn’t need to go as fast to have the same energy.
 
A good way to test this is to take a WE or marui gbb pistol, fill it up with .2’s and chrono it, for the sake of argument lets say it fires at 328fps which is 1j
Now try it with .3’s and it fires 300fps, which is 1.2j or equivalent to firing a .2 going at 370fps
 
This is why it’s important to chrono a gun on the weight you plan on using in a game, because a player can perfectly honestly, indeed without even realising himself, chrono his gun on .2’s and pass, but then fill his mags with .3’s and spend the rest of the day shooting a hot gun.
 
Now you can argue all day that “yeah but he passed the chrono”, well it’s the exact same thing as running hot, the effect is the same (ie it hurts more and he has a more range), if everyone on the site does it or is happy with people doing it then the site's limits should be changed to reflect this.
 
so digression aside what energy should you run? Well my opinion is you should take your site limit in joules and get your gun to shoot that on the ammo you use, any less will be a disadvantage and any more will be cheating.
 
Part 6- nerd time!
Well, that was a long rant without nerdy equations and whatnot so time to put our science hats on.
 
So our bb in flight has 3 forces acting on it:
Lift- from our magnus force, this is a product of our backspin and our velocity. The full equation I’ve used is for a cylinder but it’s close enough for showing the effect:
Fl=ρ*v*2*π*r²*l*ω
Looks an awful lot like it’s not just backspin and velocity there so lets break it down:
Fl is our lifting force v is our velocity ω is our angular velocity (aka how much spin we have) r is our radius l is our length (for the cylinder example I stole this equation from) ρ is the density of air so if you think about it, if we make some broad assumptions we can say that the spin doesn’t slow down (at least not enough to make a difference) and the density of air doesn’t change enough to make a difference either. Now we’re dealing with the same size of bb so really the only things that can change are F as a product of v and ω.
 
Drag- this is just from velocity and bb diameter (so sorry marushin guys but not sorry, we’re dealing with 6mm spheres here), although once again we have a more complicated equation:
F=0.5*ρ*v²*Cd*A
Ok so that’s not as bad
Fl once again is our force, only this time it’s for drag Ρ has snuck in again, it’s the same atmospheric density v is a bit of a cheat, technically it’s the velocity of the air against the bb but I’m not NASA so the velocity of the bb is close enough Cd is our drag coefficient, again a big simplification but for our purposes we’re saying 0.47 for a sphere that’s got turbulent air around it (little known pseudo fact marui “magic dust” actually bonds the airflow to the bb causing laminar flow dropping the Cd to 0.1! (*not entirely serious)) A is our frontal area of the bb, good ol’ πr² So making the same assumptions before, with the addition of assuming turbulent flow, we end up with Fd being variable as a result of v.
 
Gravity- this is from our bb weight and here comes the scary equation:
Fg=m*g
Wait, what? That was meant to be complicated! Well once again it is, technically g can depend on where on earth you are but in reality nobody cares because it’s close enough. Remember back to school math g is 9.81m/s²
 
So with that explained on to the bit where I skip the really dull bit and just tell you to go look at the spreadsheet, basically it takes these 3 equations and with the starting parameters you give it it’ll spit out a graph of how different weight bb’s will fly.
 
So as a quick note on it’s use:
Muzzle energy- I’ve rated this as fps on a .2gbb just because that’s a unit we’re all familiar with, if you want to use joules it’s to the right of the reset hop button MED distance- this is the distance of your MED, for snipers interested in just how much hurt your 500fps gun running .5g bb’s inflicts on someone at 20m Energy at MED- this gives you an MED if you want to know how far a bb goes before it slows down to a given energy, useful for showing how far a bb can go whilst still hitting as hard as an equivalent gun point blank. Reset hop- this was a right pain making the spreadsheet so unfortunately the best I can do is fix the hop setting for a 20cm rise before it drops again, this will change if the fps is different so remember to press that button otherwise you’ll get some suspiciously good range numbers and some strange graphs. Maximum range- this I’ve set to the distance I’d call the “effective” range, ie when a bb has risen 20cm from where it left the barrel, then drop to 20cm below where it left the barrel, so if you fire at a man sized target you’ll hit him without needing to fire your gun wildly into the air and assuming he’s kind enough to stand there and get shot.  
So a couple of interesting points to note:
Say we have a site, regular rifles have no MED and can be 1.3j or 375fps, snipers have 2.3j or 500fps but they have a 20m MED:
Our rifleman running .2’s can shoot 38m, but if he can get enough spin to lob a .5g bb he’ll shoot 52m Our sniper running .2’s can shoot 43m, and at 20m the hit is a measly 0.4j or the same as being shot point blank by a 205fps gun, thing is if he packs .5’s in his gun he’ll shoot 60m and more importantly at 20m he hits with 1.27 joules, or the same as being hit by the rifleman at point blank  
So with that I’ll leave you to have a little play.
 
Part 7- but I’m not a nerd! What do I need to do to get my gun to shoot far?
So we’ve covered pretty well the science of how to get a bb to go far, it needs to be heavy, with lots of energy, and enough spin and if it has those 3 things it’ll go as far regardless of what gun it comes from.
 
So why spend money on a fancy polarstar kit with an rhop like my favourite youtuber uses?
 
Well back at the start we mentioned you need 2 things to get hits, and the first is you need to hit in the first place.
This is where all our upgrades come in, a fancy barrel and hop unit wont make your bb’s go any further, but what it will mean is they’ll all start the same, we’ve all seen that guy with his 50rps dsg build m4 spray a mag load of bb’s only to get salty and rage because “he’s not calling his hits” when in reality by the time it gets to the target it’s a 10 foot spread and he's not hitting a thing.
 
So the first place I’d recommend looking is your hop unit, there’s a million different designs that promise the earth so I’m just going to cover the standard, flat and radial hop and hopefully explain what’s going on so you can understand what some of the fancier designs out there like maple leaf are doing.
So the standard hop is what most guns come with these days, it’s basically a lump of rubber in your barrel:
 

 
Now lets add the bb, the trick here is to realise that a barrel is not exactly 6mm and neither is the bb, nothing is perfect and there’s a tolerance. So when you’re buying expensive barrels and bb’s what you’re really paying for is for them to be exactly the size they say they are and in the case of bb’s to be all exactly the same size.
 
Now a bb is slightly smaller than the barrel, so we can be sure it won’t get stuck, this is why it’s important to keep your barrel and ammo clean because enough dirt and it’ll be rubbing it’s way down messing up that lovely backspin we want.
Now we want our backspin to be the same every time, not just in terms of how much backspin there is but also in terms of the backspin being the same every time:
 
The perfect scenario is vertical spin like this:
     

 
But of course the bb isn’t going to be nice and pop perfectly in the centre every time:
 
     
 
 
 
 
 
 
 
 
So our spin is at an angle, and as a result our magnus force will also be at an angle, lifting the bb not just up but sideways, this means it’ll try and curve off to the left or right, and because not all the force it acting upwards it’ll also lift up more or less, this is our friend with his ultra fast gun shooting a 10 foot spread and not hitting anything.
So our alternative is to flat hop, and try to minimise this angle:
     
 
 
 
 
 
 
 
 
Which when we try our wonky bb does this:
 

 
So we get less angle, our bb’s drift less and our spread is less, meaning our bb’s are much more likely to hit what we’re aiming at, not only that but a flat hop will have a longer contact patch, or in other words it spends longer spinning the bb, meaning we can spin heavier bb’s and get all the wonderful benefits heavier ammo allows us.
 
Flat hopping a gun really isn’t as hard as you’d think it would be and can get some excellent results for very little money, and whilst it wont give you more total range on it’s own, it will give you accuracy and the ability to use heavier ammo increasing the range you can hit things.
 
edit:
as a minor digression i figure i might as well cover how to make a flathop seeing as it's one of the best bang for buck airsoft upgrades out there as you can really tighten up the groupings of a gun potentially for free:
 
1. remove the hop from your gun, this can be very simple or very difficult depending on the particular model, for example my f2000 is just 1 pin to remove the upper and the hop/barrel is right there to pull out, but a jg ak takes much more disassembly, as with all things youtube the gun you have for a guide, take your time and remember- as long as you don't lose parts you can always take it to a tech to get it sorted, so don't worry.
 
2. pull the stock hop unit apart, you want the rubber and the nub (the little cylindrical rubber thing that'll drop out when you remove the barrel), the nub you can toss away as you'll want to replace it with a flat nub, various manufacturers (Prometheus being somewhat prominent) make these but if you're handy with a knife and super cheap you can make a heath robinson flat nub out of a pencil eraser. again youtube is your friend for how to disassemble and re-assemble a hop unit.
 
3. turn the stock hop rubber inside out, this can be tricky and i find using an alan key (or similar pokey type object) can help tremendously, don't use anything sharp though as you don't want to poke holes in your rubber (air leaks are bad m'kay)
 
4. cut the bump off the inside, as well as the ridge on the bottom used to line it up, or if you prefer there are pre-made flathop rubbers out there which will save you the bother. the important thing we're aiming for here is no holes, and no bumps on the inside of the rubber
 
5. put the hop rubber back on the barrel, but remember where the ridge was? well turn that 90 degrees from the ridge on the barrel, this way we've got the side of the original hop rubber on the barrel which will be nice and smooth (assuming like me you couldn't be bothered to fully sand down the insides and instead just spent 20s with a pair of snips during step 4)
 
6. this step is optional but recommended is to take some ptfe tape and wrap it around where the hop and barrel overlap, the idea here is to seal air particularly where the ridge cut in the barrel is that is no longer sealed as we've removed the ridge, you don't need too much or else you'll have a hard time re-inserting your barrel into the hop chamber
 
7. re-assemble the hop unit, this should mostly be the reverse of the dissassembly, with the exception that we're replacing the original round nub with our new flat nub, you may need to trim the nub a bit shorter to fit the hole in the hop unit (which will again depend on brand). now the trick here is when you've got it assembled to take a look down the barrel, turn the hop on all the way and check it's working, and also check the angle it's coming out at, if it's down too far on one side or the other this will pull your shots off to that side so we want it nice and square, the way i do this is literally to "twiddle" the barrel until everything's nice and square.
 
8. finally, drop your hop back in your gun and go pew.
 
But what if we want more? More is good right?
Well my friend in steps the Rhop:
     
 
 
 
 
 
 
 
 
Man it took ages to align that and it still looks wonky.
 
Now this might sound controversial but in my opinion the rhop isn’t really much different to a flathop, but the devil’s in the details.
 
Firstly it’s going to actively pull the bb’s into the centre, if you look at some of the fancy hop designs (like maple leaf) you’ll see they’re trying to go for the same idea.
 
The DIY rhop just takes a regular flat hop and pops a cut up square of rubber in the window of the barrel, commonly you'll see folk mentioning silicon hose or you can buy dedicated rhop patches. when it’s turned on it can end up looking very flat inside the barrel, but remember when it deforms it’ll wrap round the bb:
 
 
   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
So we get as close as we can get to perfect vertical spin every time, and we have the same longer contact patch the flat hop gave us so we can still lift heavy ammo.
 
Now remember that a bb’s lift is not just a product of spin, but also its velocity and herein lies the advantage of the rhop.
Hop up rubbers come in different hardness’s, and like formula 1 fans will tell you a soft rubber is going to be grippy and a hard rubber not so grippy, now these aren’t cars but there’s one solid advantage to a hard rubber and that’s stopping leaks- remember your airsoft gun is chucking a lot of air behind that bb and air likes to escape.
 
Now one way is to go down the barrel and shove the bb out of the way, but if it can shove its way out past the hop rubber or the nozzle or better yet just not go anywhere and stay in this nice cylinder thank you very much then it will.
 
This is why common advice is to check for air leaks. Now since we’re talking about hops we’ll simply say that if you want a soft grippy rubber to spin your heavy bb’s then it’s going to be easier for the air to squish the rubber out of the way and sneak out, so we want a hard rubber, this is why hard rubber’s tend to be recommended for snipers as it’ll help prevent air leaks, and if you’ve played with the spreadsheet you’ll see that faster bb’s need less spin to lift, so the grip is less relevant if your gun is shooting fast.
 
Well an rhop gives you the best of both worlds, because the patch and the main body of the rubber are separate you can have a nice hard air sealing rubber on the outside and a nice soft grippy rubber on the inside, yay!
 
Downside is these can be a bit of a pain to get right, however it’s worth experimenting because the boost in accuracy and by extension effective range is a worthy payoff.
 
now i haven't covered bb's barrels gearboxes and springs because frankly it's pretty straightforward:
good bb's are consistent in size, weight, surface polish and roundness, check out Gasman's topic if you want to look at what makes up a good bb. good barrels are straight, there's no variation along their length, tight versus widebore is it's own topic but in my opinion that's secondary to quality (ie if you care enough to consider proper tight/widebores you should really focus on quality too) the argument for a tightbore is that it will allow less "wobble" of the bb as it can't rattle around as much, of course the counter argument is that the tighter tolerances mean the bb could hit the barrel and as a result gain spin in a different direction pulling the shot off. the inverse is true for widebores, whilst they could let the bb bounce around more the theory is the bb will be kept centred by a cushion of air and thus not bounce on the sides and get off-axis spin. barrel length isn't all that important for accuracy, anyone who's met the wrath of my 4" pdi barreled hicapa can attest to that, although for certain setups a long barrel can be rather useful (like trying to go for a quieter build, especially with hpa) i'll let you decide for yourself which side of the barrel argument you sit on, but remember quality is absolutely king. personally i get good results from pdi tightbores, but i've not really tried proper quality widebores to compare. good gearboxes don't leak air, so they have good o rings, good tolerances and good compression, apart from that most gearbox discussions are more about supporting higher rates of fire, reliable feeding etc. and springs give you more fps, pretty self explanatory, pick the right one for your setup and site limits. edit: hop units (ie the likes of madbull or pro-win) have more sensitive adjustments, features like the addition of tracer or holding bb capability, and are generally better quality, however they are not essential when compared to the rubbers and nubs they contain  
most of what makes an hpa system so good is it gives the same pressure and volume of air for every single shot and consistency of fps=consistency of spin=accuracy=effective range, it's also much easier to achieve reliable high rates of fire and the ability to tune your fps can be handy if you regularly travel to sites with different limits, of course the price you pay for this is having to carry around the small bomb air tank on your back all the time.
 
Part 8- conclusions
Well the primary conclusion from this is that I should really be getting back to doing proper work, and that it’s almost certain I’ve just annoyed several strangers on the internet with my wonky diagrams and half-baked ponderings who will proceed to tell me I’m wrong about something.
 
Now I’m not trying to lie to you, and if I am wrong I’d like to know because at least half of what I know has been learned through internet arguments.
hell I used to think running .2’s was the best way to go for low fps until a bunch of strangers on the internet told me I was wrong. When I properly tried it to prove to myself I was right I realised I was wrong, and now look at me preaching the benefits of heavy ammo, with science!
 
The best way to learn this stuff is to try it, it might be scary to crack open your first hop unit and cut it up with a pair of snips to make a flat hop but if you’re too scared to do it the first time you’ll never be able to try it a second or third time and eventually get it right.
 
But if you think I’ve made a mistake, or I’m spreading misinformation then please explain yourself so I can understand what the problem is and either admit i'm wrong and learn something, or prove you wrong and you'll learn something, either way someone gets to learn something and:

 
now if anyone asks, i've been researching de-lamination of fibre matrix composites all morning ;)
BB range study.xlsm
 
edit 1: cleared up an issue with travel time using heavier bb's (ie it's only slower over short distances and the difference isn't that much), added a rough guide to flathopping (more as a motivation as to it being easy and effective than an actual tutorial), fixed a few spelling mistakes and changed some wording to make it a bit clearer in parts.

I definitely get where you're coming from.
 
Without going off on a tangent, after having a SCAR L NGRS I do feel they're a bit overrated, don't get me wrong it's a great gun but not convinced it warrants the price tag at 290fps stock and no mosfet etc.

I've just realised I really want a TM Berretta M9a3.

There are stories told that TM have mock ups for many guns but what gets made is dictated by what they think will sell in Japan.

PMs not loading properly today for me. They send but they endlessly loop as you send them so they appear to not send even though they do.

280 on 0.25s, 30 yards and you'll have a person size spread.
It has been a great gun to be honest.

Quick review of the Golden Eagle m870, as some are from rather dubious sources. 
I've owned all sorts from model gun company oddities to the aa12, I'm not too fussed to say if I have bought something a bit shit, frankly I'll say so. 
 
Like the WE Luger I bought and am certainly not bitter about. 
 
Anyway, It comes in a decent box, with 3 shells, and a speedloader. 
 
I'm 2,000 rounds into this gun now, backyard arsing around and a full day of cqb at the mill. It's more than the luger managed. 
 
Externally: The paint finish is average to poor, however the wood is of a relatively decent standard of finish.
The controls feel positive and there's very little wobble.
 
Skirmishing: Mine has been consistently gas tight, and you can expect 4 to 5 shells from 1 gas fill. I initially thought the gun was broken from the start, as it took a lot more effort than I expected to cock. The mechanism has taken some wearing in, getting smoother and easier as it is used. 
 
6 shot is where it's at with this, it overhops 0.25s on 3 shot, whereas on 6 shot the grouping is perfect for airsoft use and the range is more than adequate. The same can't be said for a certain piece of Chinese made knockoff ger... Getting sidetracked.
It does seem to be quite picky on shells, this may be something that beds in with further use, or it may not be., further time will tell. 
 
Something important to mention is I've had 4 or 5 jams over the course of the day, all but one very easily sorted. Most of these were this morning. This may be another case of bedding in, and is also common to the original marui. 
 
On the whole, I'd reccomend one. 
 
Unlike a WE luger, they're shit. But that's another story. 
 
 
 
 
 
 
 
 
 
 
 
 
 

Looks like the Death Star that one....

Further update. 
The hop rubber was deformed by ASG blaster's 0.25s shit quality control. 
Nothing wrong with the gun at all. 

The whole bottle I skirmished with was like this, and I never noticed as they were poured straight into speedloaders. 

Thanks for the indepth look.

I had a Prowin unit out of my G&G, with a R hopped Prommy barrel. I chopped it down, and fit it. I did get the odd misfeed, but I found after lubing the magazines it works a treat now.

Doing that will allow a small drop in FPS, hops .28's like a champ, and will allow better use of the suppressor or a tracer unit.

I really like how short it is, and how light and nimble it is. But I really must buy a high torque motor for it. So im debating a SHS high torque or a Nuprol one to keep costs down.

 

Hello there chumps.
 
Are you into the pistol caliber craze? Do you want something this is lightweight and practical? Do you want something that is better than the ARP9, lookalikes, and everything else in its price range? Then, this is the one for you. Allow me to explain why: 
 
Introduction
 
So, I stumbled into this weapon not too long ago: https://www.evike.com/products/89987/ And, I was thinking to myself: "wtf is this". I'm sure most you would think that. It is a cross between an M4 and an MP5, using an M4 body contoured towards using MP5 mags. This creates a rather unique aesthetic, one that I grew to enjoy over time. I then discovered this version: https://www.evike.com/products/94439/ A grey bodied SBR with an MLOK rail and silencer. And holy shit, this thing was cool. They are also only around 2kg! Ridiculously lightweight. Perfect for fast and lightweight-geared players like me.
 
As I waited to gather funds, this thing eventually released in the UK and EU. Specifically, the black MLOK and silenced version from Taiwangun: https://www.taiwangun.com/en/electric-3/pdw-sbr-sd-black-king-arms?from=listing&campaign-id=14&q=pdw+sbr No, this isn't the cool grey version that I wanted. However, it still looked pretty cool and classy in black. For only £160.52, this competes against all those CYMAs, NUPROLs, Specna Arms, G&G Combats Machines, and the infamous G&G ARP9. Cool looking, cheap, practical, and compatible with generic parts. It was a no brainer that I bought it as soon as I had the funds available, as well as a few CYMA 120rd mid cap mags. This totalled around £200. Patrol Base also has them and sell for £180: https://www.patrolbase.co.uk/king-arms-pdw-sbr-sd-assault-rifle?pv=10344 This is more expensive, even with shipping. And, they do not have the CYMA MP5 mid caps; only the high caps. 
 
With the miracle work of UPS, the package arrived in once piece:
 

 
I had already removed the packaging earlier from excitement. It was wrapped in black plastic wrap with a lot of rounds of bubble wrap underneath. Pretty well protected by Taiwangun.
 
Opening its contents:
 

 
More bubble wrap to secure it in place. Respectable. Removing that further:
 

 
What a clean beauty. No problems or missing items. Although:
 

 
This tag is telling me this gun is shooting too hot for most UK sites. Seems like I will have to downgrade it before I can use it.
 
This is what the small bag off goodies contain:
 

 
2 different backstraps for the grip and a flat price to replace the bump on the front. I tried on a few and I quite like the smaller backstrap: 
 

 
Though, I will keep the standard one on for now.
 
External Feel
 
Picking this gun up for the first time, it felt incredibly light which was not surprising since it has a plastic body. It has a metal MLOK handguard, not plastic unlike most people say. The plastic body has a matte finish and does not feel cheap at all. The metal handguard is smooth and has a solid feel to it. The trigger is flat and metal, giving good leverage. The stock is plastic, retractable, and does not rattle or move around when shouldered. The stock tube is also plastic and has a decent amount of space for a large lipo. The metal rods that lock the stock in place are metal with a matte finish. 
 

 
Personally, I was not planning to attach anything to rails, so I removed them to reveal the smooth and straight rail:
 

 
The rails are easily removable using a metric 2.5 hex key.
 
It has an odd but understandable design on the other side:
 

 
It is essentially an M4 body, and all they did was overlapped the forward assist area until the dustcover matched an MP5 ejection port size. Quite hilarious but logical to be honest.
 
Pulling back to charging handle:
 

 
This reveals a traditional, and shitty imo, hop up chamber. Nothing special. It does not lock back; the bolt release on the other side does absolutely fuck all.

One small problem that I immediately noticed is that the o-ring for the silencer seeps out like a fat guy's beer belly splurging out of his t-shirt and over his trousers. Not a pretty sight:
 

 
I tried realigning it several times. But, it became clear that it just would not sit properly. So, I removed it and that was that.
 
Additionally, there seem to be small tolerance issues with the body:
 

 

 
The upper and lower don't quite align exactly. However, it is still sturdy and does not rattle when handling. Therefore, this is acceptable to me.
 
The handguard wasn't exactly straight out of the box also. I rectified this by removing the handguard by the 4 screws and clamping the rail and body together using a red dot:
 

 
I then reinstalled the screws and it appeared much better:
 

 
Next, I had a go at fitting and comparing the magazines:
 

 
On the left is the King Arms magazine, and on the right is the CYMA. The quality in build difference is noticeable: the King Arms feels like a flimsy bit of plastic, and the CYMA is much more sturdy in comparison. The King Arms magazine is also slightly thinner than the CYMA. This naturally meant that the CYMA magazine was a tighter fit. However, it works just fine with a bit of breaking in:
 

 
Weighing the gun:
 

 
2042g without a mag.
 

 
2120g with the King Arms mag.
 

 
And, 2188g with the CYMA mag. Overall, super impressive weight. Around 2.2kg with a battery, mag, and BBs, is an incredibly practical package. 
 
Getting to the battery compartment meant removing the stock:
 

 
To remove the stock, there is a large button under the buffer tube that you press to release the positioning of the metal rods. When it is at its extremity, you need to push down the button as shown in the photo above to get it completely off. A small buffer tube cover is then revealed and is it super intuitive to remove:
 

 
The battery space is fairly generous and should fit the vast majority of lipo sizes out there. 
 
Test Fire
 
Unfortunately, it is a tamiya connector. So, uh, gimme some time to zip back to early 2000s and back:
 

 
So, this is how it sounds out of the box using a half-charged, 9.6v 1600mAH NiMH battery without adjusting anything:
 
 
Not bad at all. Definitely sounds better than your average midrange AEG out of the box. Fire rate isn't too shabby. But, a bit sluggish for my taste. The foam-filled silencer does make a noticeable difference in sound.
 
Now, onto the chrono. I used 0.25g Amoeba BBs which was what I had at the time:
 

 

 

 

 

 
So, out of the box, definitely too hot. The fps also kept decreasing into the borderline 300s, and I confused as to why until I remembered that this gun has the shitty traditional style hop up. It slowly unwound itself over time. The hop up chamber definitely needs to be tightened. OR, you save yourself the pain and get this for £8: https://www.ak2m4.co.uk/zci-prowin-style-hopup-chamber-plastic-m4?search=zci This style of hop up is vastly superior because it is easier to adjust and more importantly, it is similar to a worm-gear style design where it cannot unwind itself.
 
 
Overall, nothing special which was to be expected with stock performances.
 
The Deep Dive Into the Internals
 
WooOOOoooOoOOooOoo... Time for some spooky voodoo stuff.
 
Disassembly is just like any generic m4. Simply remove this first pin at the front of the receiver:
 

 
This pin just falls out; there is no pin in the receiver to hold it in place like many other M4 AEGs.
 
Pulling apart reveals the gearbox:
 

 
And like a regular M4 AEG, the hop up and barrel assembly is housed in the upper receiver.
 
The hop rubber looks like a traditional nub:
 

 
Nothing special and gets the job done. The barrel is also very clean too. Websites say that it is a polished 6.05mm brass barrel,
 
Comparing to my custom M4 AEGs: ZCI rotary chamber, 229mm ZCI steel barrel, maple leaf macaron and omega nub:
 

 
If I were to install the custom M4s hop assembly into this gun, the foam sound would be more pronounced as the stock inner barrel does protrude quite far into the silencer:
 

 
Removing the stock is pretty easy, just like a standard M4:
 

 
Removing the mag release requires a metric 1.3 hex key:
 

 
You do not need to remove the MP5 style mag release to disassemble the gearbox.
 
The body pin and rear gearbox pin comes out with a pin and a hammer:
 

 
Then, the motor grip:
 

 
Comes out as expected:
 

 
The motor does not have any markings. I can also turn the pinion very easily which indicates that it is not very torquey.
 
After all those components are removed, the gearbox can be pulled out:
 

 
Looking inside the lower receiver, seems to be just as high quality:
 

 
Then, I was pleasantly surprised by something:
 

 
Quick change spring! This feature is a godsend as it makes the assembly process so much easier. And, as you can see, there is a small unit just below which is the mosfet.
 
Taking it out, however:
 

 
It's stuck... the spring is attached to the piston which is a bit of a lame move 😕
 
Nonetheless, the gearbox disassembly is a straight forward process since it is just a standard V2:
 

 
And revealing its contents:
 

 
The trigger spring is incredibly stiff, more so than normal. I do enjoy the red colour scheme. The contrast provides some nice eye candy.
 
A close up on the mosfet unit:
 

 
It stays in place with a single screw and does not wiggle at all. And as you can see, the grease is very stringy on the gears. Not very nice to be honest. Spinning the gears makes it look like I'm weaving silk. The gears are standard 18:1 and of decent quality. I can't comment on durability yet, or ever. Because I will be changing them out to create a high-speed build. This guy preaches about it though: 
 
 
 
Gearbox has a nice gap here to push the anti-reversal latch if the gearbox ever locks up:
 

 
Testing the compression:
 

 
It is excellent. I can't push the piston forward with my finger over the nozzle. Genuinely amazing seal for a stock gun of this price.
 
What the stock AOE looks like:
 

 
Not great. But, the standard for stock AEGs. Should last a good while like this, assuming everything else is stock.
 
Setup to test the stock shim job of the gears:
 

 
Testing the sector gear:
 

 

 
Has more than 0.5mm of travel. Leaves a bit to be desired.
 
Spur gear:
 

 

 
Seems to be about more of less 0.3mm of travel. Not too bad for stock.
 
And for the bevel:
 

 

 
Seems to have about 0.1 - 0.2mm of travel which is excellent for stock. Overall impressive.
 
The gearbox is even radiused at the top and bottom:
 

 
Now for the spring... it is attached to piston and requires a very long screwdriver to get out. Otherwise, you fight the spring tension which isn't nice (excuse blurry photo):
 

 
Which reveals a disc:
 

 
This is easily popped out with a bit of force:
 

 
However, you will need the disc when reassembling the piston. Otherwise, the piston head will be loose.
 

 
The reassembly is super smooth too:
 

 
The anti-reversal latch does not pop out like a maniac, unlike most V2 gearboxes. And, with the quick-change spring, I don't even need to hold anything down when putting the other half back on. This makes reassembling incredibly easy and pleasant to work on.
 
This gearbox is super impressive. By far and large, one of the best gearboxes for the price. This is even better than some of the higher up, premium price tag stuff.
 
Quick Comparisons
 
At £160.52 currently, this is roughly around the prices of many Combat Machines and Specna Arms rifles. I cannot comment on Specna Arms as I have not used one before. However, G&G Combat Machines I have. I have also wielded the ARP9 myself which is its direct competition which I will be mainly comparing it to.
 
If we start with combat machines, I recently worked on one of these which are very common rifles: https://www.patrolbase.co.uk/g-g-combat-machine-cm16-raider-2-0
 
They are decent guns for the price. However, the gearboxes are of lesser quality in comparison: no mosfet, worse shimming, worse compression, worse piston quality, no anti-reversal hole. The barrel quality is also worse. Cannot comment on the gears, but I'd imagine they are similar in quality. The overall construction is tighter on the King Arms compared to the combat machines. King Arms have been known for their tight construction, especially on their higher-end guns. Maybe not all bells and whistles since the construction on their MDT LSS, that I had for a while, was so tight that some parts of the metal had to be cut with a dremel to disassemble the gun...
 
Now, compared to the ARP9, the definitive reasons to get the PDW SBR over the ARP 9 are:
 
Gun itself is cheaper Bigger battery space  Mags are significantly cheaper Midcaps hold more rounds (60 vs 120) Less crazy, space-gat looking than the ARP9  
Of course, not to say that the ARP9 is a bad gun. It is definitely a gun that is good, popular, and worth the price that it is at. It's just that these features of the PDW SBR (the looks got me tbh) make me prefer it over the ARP9.
 
 
Verdict
 
Time to list some pros and cons.
 
Pros:
Cheap, entry-level price High-quality plastic and metal construction (SD version) High-quality gearbox Quick change spring Lightweight Short Customizable grip Compatible with most conventional V2 parts Super cheap extra midcap mags SD version has a cool foam-filled silencer Polished 6.05mm barrel  
Cons:
The mag that it comes with is flimsy and a loose fit Weak motor Shoots hot out of the box Some small fitment issues  
Overall, this is a top recommendation. For the price you pay (£160-ish), this thing punches so far above its weight, and it is an incredible base for a high-tier performing gun due to having a standard V2 gearbox and a normal M4 hop chamber. There are only a few rifles I can think of that can compete against the PDW SBR in terms of practicality: one being the ARP9, another being the ARES pistol M4 series. I have yet to get a hold of the ARES gun, so I cannot comment on that. However, I have seen decent DSG builds which utilize the ARES ETU.
 
This is my new main weapon now. Gotta upgrade the shit out of this thing, internally. Externally, gonna keep it mostly stock to minimize the weight. A red dot with a riser at most.

Groundzero_1.mp4





Tried many camos.i am a real fan of all camos good and bad......but have to think of the environment I play in if it's going to belp me during the game and I have found multicam tropic to be brilliant.dont see too many people in it either which is nice.

This one isnt mine, but it's just fantastic.
 
An airsoft lemat revolver with a functioning grapeshot barrel to boot.

hahah Yes I've had it since.. well a VERY long time!
...abit like this...
 
Marushin M1 Garand (GBB) with 10x 8rnd clips (8mm)
Bespoke CO2 tank in the stock for 16g CO2 cartridges
Tanio Koba rifled inner barrel

Usually whatever is on Planet Rock at the time.
 
However at camp at the NAE etc you can usually hear this drifting from our team camp
 
 
And at some point inevitably this will come on
 
 

I could post music all day dude. Im a music guy, its a vital part of my daily life 🙂
My mother is deaf in both ears, requires 2 of the most powerful hearing aids known to man kind cranked to full power. She cant hear music the way I do and its got to be one of the worst things I can possibly imagine.
This lockdown has cancelled/postponed so many of my planned gigs this year... im gutted... 
This is another one of my favourites. The drum drop at 2:40ish sends shivers down my spine each and every time.
 
 
 
And they only went and used it in one of the coolest episodes of Sons of Anarchy...
 
 

Too right 👍

@LoneTactix 👋
Interesting got me hyped and I didn’t do anything.... but now.... I want to play a game of Airsoft.... it’s been too long, hopefully soon!!!! 😜🤞
😎👍
💷GAMBLE💷

With a mix of driving, gaming and 80's action film style songs, check out this channel: 
https://www.youtube.com/user/NewRetroWave
Example song for psyched-up airsoft purposes:
 

This could be yours for the princely sum of £60 on discord.
 
Shame a brand new one costs £61 from TaiwanGun.

Yeah, It can be hard to find out how to check since the online self check has been down for years.
 
I always called 'Fire Support'
They won't give you info but will confirm if a name or address is correct for that number

Classic Army M249
 
WE 416 GBBR

 
G&P 16" Recce Rifle

 
WE Sa80 GBBR

 
KWA Kriss Vector and ICS Mp5a3

 
WE M4a1/M203 GBBR