Ballistics and how less power is more energy delivery.

[AirSniper]

I see and hear often about people wanting to and looking to power up their RIFs to the maximum permitted on anyone site.

People seem to think that throwing more energy in to something will make it go faster and that contrary to what is believed, it is counter intuitive to use lower power as its often more effective.

The best demonstration of this reality is a youtuber that made a video about his fire arm that was a PCP based rifle, long barrel and the calibre to make your eyes water but the principle is still the same, you just have to imagine that the 1150 grain slug is 3.08 grain BB (aka 0.2g)

So rather than me going on about it, watch the video and first be stunned at the pure awesome that helium is and then check your faces on the shots of the ballistics gel and the high speed camera.

You will see in the demo that the power in PSI from the High Pressure Whip in play, is lowered in stages to find the "Sweet spot" in the power setting to both gain accuracy and delivery of the energy, so it dumps that excess and as you can see what the 1150 grain pellet does is pretty scary. 

So apply that principle to airsoft guns, less power means better results all around, its a question of finding the sweet spot for your BB's to deliver the whack they need to. 

 

[Rogerborg]

So apply that principle to airsoft guns

If anyone is penetrating right through their targets with an airsoft BB, I think that might be a bit of an issue.

It's an interesting demonstration of how higher pressure gas / more puff doesn't necessarily impart more energy to the projectile, but it applies only to that pressure and that projectile.  The energy involved is so far beyond airsoft levels that I'd be surprised if we saw a similar effect.

However, airsoft is nothing if not surprising, so if any HPA Ghostbusters fancy try to to replicate that, I'd be very interested to see the results.

That's all before the BB leaves the muzzle though.  At the point where it emerges, the only ballistic considerations are angular velocity (backspin), and linear velocity (fps / Joules).

Sufficient backspin to fully hop that mass of BB + the maximum permitted kinetic energy for that BB = maximum range, and maximum energy delivered to the target at any range.

Effective range might be different if you get more consistency with less muzzle energy, but not maximum.  Even if you're lobbing a bit rather than trying for "laser accuracy", it's all about the linear velocity, and more is more in airsoft.

 

[AirSniper]

LOL, yeah I'd concerned too...

However, the same laws of physics and thermodynamics applies to airsoft as it does to airguns and real steel.

The laws of thermodynamics can't be broken, you can not get more energy out of an item that you have input.

Likewise, input too much energy and its just wasted energy as the projectile is unable to dump its energy, you know BB's that really hurt... thats effective power from the output and BB weight.

Ballistics works no mater the scale, so a 0.2g BB with too much fps is not as effective as one that is lower with the right BB weight, this is where joule creep comes in.

 

[Samurai]

Those seem to be some soft metal slugs. My guess is that it works like a bullet, and expands into the rifling. The more pressure it has behind it, the more it expands, creating more friction and slowing down the slug.

 

[Rogerborg]

Those seem to be some soft metal slugs. My guess is that it works like a bullet, and expands into the rifling. The more pressure it has behind it, the more it expands, creating more friction and slowing down the slug.

Or its blowing enough gas past the slug to create eddies in the space time continuum inside the barrel.

 

[Tommikka]

There is something to be said for this.

I don’t know how well it would apply to airsoft as you’re firing a plastic ball which will randomly spin unless it has some backspin applied etc

Airsoft physics will be close to musketry 

In paintball there can be a degree of compression in the barrel depending on paintball quality, and it’s arguable whether or not rifling has any benefit.

A particular company did market their range of size matched barrels which were available in smooth or rifled bores. Their user instructions advised to:

Use paintballs of a suitable quality 

Size match paintballs to the barrel

(There are arguments to support matched bore, undersize and oversized bore)

Adjust the internal regulator to the velocity as per site rules

Test fire against a target at desired range

Adjust velocity down until the optimum target grouping

With 280fps being the general standard for recreational paintball the optimum consistency of a bore matched quality paintball could often be around 260-270fps

If you then change to first strike paintballs which are half a sphere up front with fins at the back.  The fins cause spin in flight, and some people prefer a rifled barrel to impart spin inside the barrel

They are lighter so the air pressure needs to be dropped to maintain the correct velocity in FPS, but the different physics of the first strike maintains its energy making it fly further and hit harder at range despite being lighter

With underbore in paintball you sacrifice efficiency by surrounding the ball with a cushion of air while it’s in the barrel

With underbore you compress and force the ball through a smaller barrel, risking barrel breaks if the ball is too delicate or the batch is inconsistent 

 

[EDcase]

I don't think the video has any relevance to BB ballistics.

First off he's using hollow points which don't have an equivalence in airsoft.

What he's 'discovering' is the well understood projectile speed vs impact damage trade-off.

This is the fundamental dilemma between the two most common military rounds.

Slower 7.62 will do more damage to un armoured target but less penetration to armoured ones.

Higher speed 5.56 has more penetrating ability for armoured targets but less damage to unarmoured ones.

But none of this applies to BBs using the magnus effect.

 

[AirSniper]

Airsoft physics will be close to musketry 

Still, ballistics rules apply as they are real world physical elements that affect the BB, gravity being one of them.

It scales, that is it... I posted this in another comment about someone moaning about the joules and fps they were getting with a heavy BB, so after several posts trying to reiterate the point of physics and thermodynamics. 

What I did was distil it down to this, a diagram that illustrates the actuality of what is going on with all projectiles fired out of a barrel. 

The Joules of the weapon is fixed, why it is the fulcrum or balance point.

Want faster FPS, then lower your g weight of the BB's

It can't get any more simpler than that.

View attachment 80887

I don't think the video has any relevance to BB ballistics.

It does though.

It scales, it has to as its the same laws of thermodynamics you are bound by.

You use the algorithm for Joules to fps when you play airsoft to chrono your RIFs and you are using the very same ballistics calculations that real steel uses.

It scales, thats the thing, your airsoft is bound by the same laws of physics and ballistics as any other weapon that throws a projectile, gun, bow and arrow, catapult, sling shot, blow pipe... Airsoft RIF's... It is all the same, a projectile, energy and the elevation determine the distance and flight time and the power delivery from the power source that imparted energy on that projectile. 

 

[EDcase]

BBs don't deform on impact so the energy dissipation is not equivalent to hollow point bullet dynamics.

Energy dissipation is proportional to projectile cross section area which is why hollow points dump all the energy so quickly.

Energy = 1/2mv²  Where m=mass and v=velocity

Because it doesn't deform the energy dissipation of a BB will not change so lowering v will result in less energy at the target.

 

[AirSniper]

Again, deformation is irrelevant at this scale, were talking about energy being imparted and what it will deliver.

Point again is to demonstrate that ballistics calculations still are valid, maybe not as accurate but the fact that BB's are weighted and gravity exists as well as that pest we call time, you have then got a ballistics trajectory or its path of travel through its arc of travel.

I don't see why people are having such a hard time getting used to the idea that the relationship to energy delivery is the same no matter what scale you use.

Increase the joules as in move to air weapons levels, the same rules apply, they apply to everything that can throw or make a projectile move, including throwing rocks... earliest example of the relationship man found between throwing a stone hard and hard enough to polax an animal to subdue it or kill it. 

Its all around you and yes, even when I was training to be an FLT (among many thing) the relationship of KE to the mass being carried, forces in motion, etc, all part of the same thermodynamics that we are governed by, showed how if you were stupid, you ended up being flattened by a 4,000 lb battery if you tipped the truck over because of excessive speed.

The same rules apply to airplanes that crash, they know what sort of foot print to look at when they know things like angle of attack, speed, weight of craft including passengers and so on, can work out if its going to be recoverable as there have been some ballistic speed air crashes where there was nothing left but a scar and nothing could be recovered.

So the relationship of energy, weight and speed is a like a holy trinity, you can't break it, you can't escape it, well with enough velocity to leave this planets surface you can... but thats another story. 
 

 

[EDcase]

Perhaps I misunderstood your original point but if you're saying less speed equals more energy at the target then you've got something wrong there.

 

[AirSniper]

No, Less speed on a heavier BB at the rated joules. that is what you sacrifice when you go heavier.

You want faster, then put in a lower weight BB.

I have pointed out that the calculations are a balancing act.

The slower moving BB at the rated joules on that weight BB will result in a bigger delivery of energy as the heavier BB can retain its energy longer and deliver it more efficiently moving slower than a faster moving BB that won't be as effective of delivering its energy.

If you stood at a distance and lit up a target which would record your impacts from the BB's and worked your way from 0.2g to 0.4g, at some point you will see a sweet spot where the joules of the pistol or gun deliver the energy efficently as the FPS will be at that peak.

Key elements have been discussed and shown in effect in the helium gun, same principles, his demo showed that higher pressure was not as effective as lower pressure and that in terms equates to joules of energy, as his fixed point was the grain weight of his projectile, what was being moved around was the Joules.

OR... in pictorial terms, this was his equation, its still the same equation but the results are different as the measure is on the Joules energy and feet per second.

View attachment 80892

an over simplification as there is a "Bell Curve" to this type of maximising equation as it then swings back to slower after a peak.

Its peak being when the J and FPS are balanced.

 

[Adolf Hamster]

No, Less speed on a heavier BB at the rated joules. that is what you sacrifice when you go heavier.

You want faster, then put in a lower weight BB.

I have pointed out that the calculations are a balancing act.

The slower moving BB at the rated joules on that weight BB will result in a bigger delivery of energy as the heavier BB can retain its energy longer and deliver it more efficiently moving slower than a faster moving BB that won't be as effective of delivering its energy.

If you stood at a distance and lit up a target which would record your impacts from the BB's and worked your way from 0.2g to 0.4g, at some point you will see a sweet spot where the joules of the pistol or gun deliver the energy efficently as the FPS will be at that peak.

when it comes to airsoft projectiles when you do the math on this it ends up pretty linear:

for fixed bb weight, more energy at muzzle also means more energy at every point along its flightpath (including extending said flightpath)

for fixed energy, more bb mass means the same energy at the mozzle, but higher energy at every point along its flightpath (including extending said flightpath)

any combination of both (more energy and more bb weight) increases both. it is also possible for a given range that a heavier bb fired at a lower energy can land with more authority than a lighter bb fired at a higher energy.

there was some discussion a while back about the "drag crisis", most notable for its implementation with the dimples on a golf ball, but best i can make out our bb's are too small and travelling too slowly for this criteria to matter.

as for when it hits a target, well generally speaking our bb's don't really deform nor do they penetrate their target, so the energy transfer is pretty much whatever energy the bb has at the time.

 

[Rogerborg]

I think you may be over-thinking this a bit.

It's interesting to see too much puff equalling less energy at the muzzle. That could, possibly, be relevant to airsoft, maybe.

But in terms of ballistics, and energy at the target, it's just angular velocity and linear kinetic energy when the BB leaves at the muzzle that matters to that BB (and to us), not how it's imparted.

Get the angular velocity (backspin) right and you'll get the straightest possible flight thanks to Saint Magnus.

After imparting the perfect angular velocity, if you get the linear kinetic energy at the muzzle maximised for the site limit, you'll get the maximum possible range, and the most energy delivered to target.

I'm not really sure what else there is to analyse. We know that heavier BBs will retain that energy better due to the the cube nature of air resistance versus the square of velocity.  And I've been careful to talk in terms of energy, not speed, for the linear component.  I'm not even sure if you're saying that it's possible to somehow get more range out of less linear energy at the muzzle - I hope not.

 

[Adolf Hamster]

I'm not even sure if you're saying that it's possible to somehow get more range out of less linear energy at the muzzle - I hope not.

it is technically possible, depending on the difference in energy, and difference in bb weight used.

for example (and i haven't checked these numbers) if you were talking a 0.48g fired at 1j compared to a 0.2g fired at 1.3j then the 0.2g would lose energy faster, and at some distance would pass the 0.48g bb and from that point on the heavier bb would have more energy at range.

combine that with the fact that as the 0.2g slows it falls further out of the sweet spot for magnus lift and it magnifies it even further.

however if we're talking bigger energy difference, say 0.48g at 0.5j compared to 0.2g at 1.5j then it'd be a different story.

 

[Rogerborg]

and difference in bb weight used

OK, to be specific, I mean that for any given mass of BB, there's no rational argument to be made that less energy at the muzzle = more range or more energy at the target.

I get that in airsoft we tend to have a limited amount of puff to impart down a limited length of barrel, and there may be cases where some mass and muzzle energy of BB goes further/hits harder than another mass and muzzle energy of BB, given the limited puff we (generally) have available.

However, the context is an experiment where he had an excess of puff, enough to actually reduce muzzle energy.  That's interesting to see, but not hugely relevant to us, since it doesn't really matter how we tune our muzzle energy down to the site limit, just that we can do it.

 

[Adolf Hamster]

OK, to be specific, I mean that for any given mass of BB, there's no rational argument to be made that less energy at the muzzle = more range or more energy at the target.

ahh yes, that does seem to be the case, as i mentioned it doesn't seem the "drag crisis" which could do something like this, applies to airsoft.

However, the context is an experiment where he had an excess of puff, enough to actually reduce muzzle energy.  That's interesting to see, but not hugely relevant to us, since it doesn't really matter how we tune our muzzle energy down to the site limit, just that we can do it.

Internal mechanics are a whole different kettle of fish. there's a lot of work could be done for example in looking at pressure curves for given energies and barrel lengths/diameters to find out if there's an optimum.

so say an Xmm barrel with a Ymm wall clearance to the bb has the most stable airflow around the bb at X energy, what wall clearance would be needed to acheive the same stable airflow for a shorter barrel to acheive the same level of stability? where do the limits lie?

and that's before even considering the requirements for achieving this, such as for a given volume of cylinder whether it's better to have a full stroke piston that will start compressing with the piston already at a higher velocity, or a short stroked piston that starts at a lower velocity but has a stronger spring to compensate.

there's plenty of anecdotal based information, eg folks saying "x-y" is the optimum barrel length, or "use widebores for X application tightbores for Y application" but i've not seen any hardcore nerd-time testing/simulation on the subject. i suspect any benefit within the extremes is probably small enough that getting a system consistent enough to even notice would be it's own challenge.

the real answer of course, is whilst it's fun to think in hypotheticals, those who say "screw that, just get closer" do have a valid point

 

[EDcase]

I believe what the video shows is the guy finding the best energy/speed for the hollow point to open fully to its maximum without over deforming.

The higher speed/energy caused the bullet to deform too much (hollow point folding over itself or tearing the rim off completely) resulting in a smaller cross sectional area therefore higher penetration.

Again, this has no relevance to BBs

 

[AirSniper]

Ok, how about this?

Fact - Your Joules is fixed.

Your variables are BB weight or Velocity.

So where are your joules going?

Simple, if you want speed, you put your Joules in to velocity by lowering BB weight.. Tadah!

Likewise, you want your joules in the BB, then you lower your velocity.

You can not defy the laws of physics, even if you pump more joules in to the system, you are never ever in an eternity going to get more out than you put in... Scientific fact, anyone who has done physics or a science that relied on energy input to follow on a process, your only concern is not the input energy but where it's going.

So think of Joules as a fluid that flows to what you want to do, there is a trade off and that is you sacrifice something.

Ballistics even works in space of all places as there is still gravity in space, although not as strong as being stood on a planet, the gravity affect the projectiles, if gravity wasn't a factor then the Apollo missions would be floating off in to deep space with corpses in the capsules... because ballistics and trajectories and gravity count, you had things like the velocity of craft, doing what, about the speed of bullet, the weight of the craft and then sling shot around the moon. Approach too fast or on the wrong course, your done for... 

The same rules apply to you in your car when driving, you hit something, were do you thing that energy goes?

This is something so fundamental that you are affected by it just by standing on this rock and anything that is thrown about on it.

So, where do you want your joules to end up? In velocity or Energy delivery in the BB?

View attachment 80903

 

[Rogerborg]

I believe what the video shows is the guy finding the best energy/speed for the hollow point to open fully to its maximum without over deforming.

The higher speed/energy caused the bullet to deform too much (hollow point folding over itself or tearing the rim off completely) resulting in a smaller cross sectional area therefore higher penetration.

Again, this has no relevance to BBs

Yarp.

From a quick skim through it, he also seems to be saying that he got lower muzzle energy with higher gas pressure, or viewed another way, higher muzzle energy by putting a bit less puff behind it.  To be honest, I didn't really watch it, I don't think there's much for us to lean here, no matter how many spherical see-saws free-falling in a vacuum get postulated.