Barrel Length Vs Range and Accuracy

[doa88]

Hi all

 

 Disclaimers first, apologies if this the wrong place to post this or it’s been discussed before. I did try searching for it but failed, so, here I am. 
 

 I have a general question regarding the relationship between range/accuracy and barrel length on Airsoft Rifles. I mention specific guns below but am really interested in the general theory. 

 

I have a krytac vector at the moment that has a longer barrel concealed behind a mock suppressor. It’s a great gun but the barrel length is a bit frustrating for CQB. I play CQB more than outdoor so thinking about selling the Vector (there are other things I dislike about it, not just this) and buying something short. Like a G&G ARP 556.
 

However, I’m worried that if I do buy this, then when I go to play outdoor I won’t have the same accuracy at range that I have now.

 

I don’t really want to own two guns and have zero technical skill for swapping barrels and hop ups and all that. 
 

 So the question then. How much difference is the shorter barrel length likely to make at 20-30m? 
 

Thanks in advance for tips and thoughts. 👍

[Steveocee]

Barrel length has 0 effect on accuracy in airsoft.

[Speedbird_666]

9 minutes ago, Steveocee said:

Barrel length has 0 effect on accuracy in airsoft.

 

Except when the barrel is 0cm long. That has a pretty big effect...😉

[EDcase]

17 minutes ago, Steveocee said:

Barrel length has 0 effect on accuracy in airsoft.

True in principle but I duno about 0 ☺️

I doubt a good pistol would have the range and accuracy of a good rifle.

 

But yeah, assuming all the internals work perfectly a few centimetres here and there don't make any difference.

The complete setup will have more influence on range and accuracy.

[Shaydee]

No difference bar the extremes, like having a barrel so long that your air volume can't cope or something so short there's nothing to stabilise the BB. The key to accuracy in airsoft is consistency, so good barrel and bb quality, a hop up unit and rubber that act the same every shot and an FPS that doesn't fluctuate all over the place.

[Asomodai]

I'd say anything beyond 200-250mm sees no impact on range and accuracy in of itself. Longer barrels may have higher FPS which could effect range to a certain extent. But then again depending on the cylinder setup you might not have the volume to lift heavy bbs straight and true for the entirety of its effective range due to undervoluming. 

 

Quality of the barrel is more important then length. 

 

The longer the barrel the more problems you introduce and the more limited your setup can become. 

[Albiscuit]

I LOVE smgs and do not feel outranged in the field using my krytac vector (standard barrel) scorpion evo or Tm gas mp7, except when facing snipers...

 

now when I had my combat machine then I felt out ranged and out gunned by most people.

 

get a decent reliable weapon and it should hold its own.

heck my pistols are nearly as good for range as my primaries and that’s out of the box

 

[Speedbird_666]

Shall we mention widebore vs tightbore? Or is that too much....😜

[Davegolf]

Barrel lengths under 200 on AEGs will limit the accurate range to around 40M with everything tip top.

 

200-250mm sees an increase to around 50M

 

250-350mm sees around 60M

 

All based on AEG, 1J power.

Gas is another kettle of fish.

 

If you want a 'one-gun' I strongly advise getting a 200-250 barrelled gun.

 

A P90 is prime candidate, 225 barrel, gun overall length shorter than the ARP556

 

Alsoco sided going to a "9mm" type sub gun as this will knock an inch off the gun length right away.

(MP5, ARP9, UMP)

 

If you switched to gas/GBB you could run a Glock carbine with a 150 barrel which would get you up around 55M.

Or other things such as MP7.

A standard TM MP7 GBBR will do 50+M

 

[Steveocee]

1 hour ago, Speedbird_666 said:

 

Except when the barrel is 0cm long. That has a pretty big effect...😉

Got me on that one.

 

1 hour ago, EDcase said:

True in principle but I duno about 0 ☺️

I doubt a good pistol would have the range and accuracy of a good rifle.

Most Mk23 pistols will outrange AEG's and usually more accurately as well. My £40 STTi with a £25 crazy jet, £6 autobot and £15 TDC outranges my buddies £400+ VFC 416A5 (much to his annoyance), it's also far more accurate and consistent.

 

 

16 minutes ago, Speedbird_666 said:

Shall we mention widebore vs tightbore? Or is that too much....😜

You can if you feel it will make a difference, would a 200mm length wide bore be as accurate as a 400mm length wide bore barrel? The context is comparitive length not bore size.

 

[EDcase]

53 minutes ago, Steveocee said:

Most Mk23 pistols will outrange AEG's and usually more accurately as well. My £40 STTi with a £25 crazy jet, £6 autobot and £15 TDC outranges my buddies £400+ VFC 416A5 (much to his annoyance), it's also far more accurate and consistent.

Yes, that shows how much all the other components count.

I'm talking generally with everything else being equal

[Adolf Hamster]

as has been mentioned barrel length itself is secondary to a lot of other factors.

 

what's more important is the barrel quality, straightness, bore consistency, internal finish etc.

 

the other contributing factors like the voluming, fps consistency, ammo quality/weight and hop all have much more effect on practical range/accuracy.

[Zarrin]

Actually I have a similar follow up question as the OP with regards to GBBs.

As @Davegolf said they do seem to have some other considerations: in my mind it probably has to do with gas expansion rates between compressed air and a propane derivative like green gas and the extra time and space they have in a longer barrel to accelerate the bb - though I don't know a great deal about the topic and could be wrong. 

 

I have a crazy jet and maple leaf rubber in my sig - these two components greatly increased the guns accuracy and consistency over stock.

As i've mentioned in a previous thread I mean to put a suppressor on there and upgrade the 80 or so mm barrel to 230mm barrel of the same type.

 

Now with a GBB that should cause a marked increase in fps and potential accuracy.

 

Can anyone give an idea of just how much?

 

And also an explanation of why condensed rapidly expanding gases like propane would be more effected than just compressed air would be appreciated! 

 

[Adolf Hamster]

2 minutes ago, Zarrin said:

Actually I have a similar follow up question to the OP with regards to GBBs.

As @Davegolf said they do seem to have some other considerations: in my mind it probably has to do with gas expansion rates between compressed air and a propane derivative like green gas and the extra time and space they have in a longer barrel to accelerate the bb - though I don't know a great deal about the topic and could be wrong. 

 

I have a crazy jet and maple leaf rubber in my sig - these two components greatly increased the guns accuracy and consistency over stock.

As i've mentioned in a previous thread I mean to put a suppressor on there and upgrade the 80 or so mm barrel to 230mm barrel of the same type.

 

Now with a GBB that should cause a marked increase in fps and potential accuracy.

 

Can anyone give an idea of just how much?

 

And also an explanation of why condensed rapidly expanding gases like propane would be more effected than just compressed air would be appreciated! 

 

 

ok i'll have a crack at it.

 

the amount of fps change is a tricky one to quantify, it depends on the original barrel length and the new barrel length, so for example adding 3" to a 3" pistol barrel is going to yeild much bigger increases than doing the same to a 12" rifle barrel. the same thing with joule creep where it depends on the weight difference between the ammo. personally i wouldn't bother, especially as hanging a suppressor on the end isn't going to help the cycling.

 

the reason propane tends to be more affected than air (although air can still have a significant effect for example in hpa systems where the feed pressure is constant) is the whole "wet steam" effect, basically (whilst dodging the complex thermodynamics behind it) when you turn a gas into a liquid or a liquid into a gas it takes a lot more energy than just heating up the same amount of material in either phase, if we take a pan of water as an example, it'll heat up just fine until the water starts boiling, then it'll hold around 100 degrees until all the water evaporates off then the temperature will rise again, adding more heat in general just makes the boiling happen faster rather than a rise in temperature, it's a handy natural method of temperature regulation hence it's use in cooking.

 

for our propane systems it's the same phenomenon only with pressure (pressure, volume and temperature are of course linked in gases), the same reason the water's temperature remains relatively constant under boiling means our mag pressures stay relatively constant. part of the reason we get the likes of cooldown or poor cold weather performance is because there's not enough heat in the environment to keep boiling the propane and producing gas faster than we're venting it out the barrel (in our pan example we've turned down the hob and it ain't boiling as fast). for example if you've ever vented a mag against a hard surface you'll see the liquid sit there and boil (mandated HSE announcement: don't touch the liquid, it'll suck all the heat from your fingers and freeze them). propane in this case is used as it's possible to keep it at a high enough pressure to maintain the liquid phase without requiring ridiculously over-built pressure vessels or artificial cooling systems (eg when rockets use methane or hydrogen they actively cool the tanks). i have heard some talk of people using other gases such as propene which are supposedly a bit better in colder weather due to a lower natural boiling point.

[Zarrin]

48 minutes ago, Adolf Hamster said:

 

for example adding 3" to a 3" pistol barrel is going to yeild much bigger increases than doing the same to a 12" rifle barrel. 

 

Yeah this is what I assumed to be the case. Though I thought there would be more too it based on the nature of the propellant gases... could be over thinking it as usual though 😵 

 

48 minutes ago, Adolf Hamster said:

the reason propane tends to be more affected than air (although air can still have a significant effect for example in hpa systems where the feed pressure is constant) is the whole "wet steam" effect, basically (whilst dodging the complex thermodynamics behind it) when you turn a gas into a liquid or a liquid into a gas it takes a lot more energy than just heating up the same amount of material in either phase, if we take a pan of water as an example, it'll heat up just fine until the water starts boiling, then it'll hold around 100 degrees until all the water evaporates off then the temperature will rise again, adding more heat in general just makes the boiling happen faster rather than a rise in temperature, it's a handy natural method of temperature regulation hence it's use in cooking.

 

for our propane systems it's the same phenomenon only with pressure (pressure, volume and temperature are of course linked in gases), the same reason the water's temperature remains relatively constant under boiling means our mag pressures stay relatively constant. part of the reason we get the likes of cooldown or poor cold weather performance is because there's not enough heat in the environment to keep boiling the propane and producing gas faster than we're venting it out the barrel (in our pan example we've turned down the hob and it ain't boiling as fast). for example if you've ever vented a mag against a hard surface you'll see the liquid sit there and boil (mandated HSE announcement: don't touch the liquid, it'll suck all the heat from your fingers and freeze them). propane in this case is used as it's possible to keep it at a high enough pressure to maintain the liquid phase without requiring ridiculously over-built pressure vessels or artificial cooling systems (eg when rockets use methane or hydrogen they actively cool the tanks). i have heard some talk of people using other gases such as propene which are supposedly a bit better in colder weather due to a lower natural boiling point.

 

Okay interesting - it sounds as though I'm missing some core foundation knowledge to fully understand it for myself to be honest and may need to do some further reading. But what you are saying defo helps explain the deficiencies in the propane based gases 👍 

 

What I still don't understand and i don't think is touched on in the above is the correlation between barrel length and it's effect on fps increase in compressed air systems like that of an AEG versus gas (other than ofc the vast difference in percentage increase in barrel length - a pistol's going up by over a 100% and then an AEG maybe getting a 20% boost in length)   

 

I believe I understand the core principle of barrel length to speed/power - taking a real gun as an example, the explosion inside the cartridge propels a bullet forward and while it is being propelled forward through the barrel it is gaining speed, once it leaves the barrel it immediately starts to drop speed, hence a longer barrel gives the projectile more time and length to gain speed.

So the reason an M16 has a higher muzzle velocity than an M4 is that in that extra 5.5 inches of barrel the M16's bullet has continued to speed up, wheres the bullet out of the M4 exited 5.5 inches earlier at a lower velocity.

 

And i do believe you can essentially apply the same principle to an airsoft gun - the nature and source of the propellant being the main difference. The reason (again in my mind) that gas gun's might be more effected than compressed air, is that propane has that fast expansion rate, so that longer barrel may be giving the BB more time to accelerate with a higher rate of expansion behind it from the propane than that of compressed air - and by that i obviously mean the compressed air at the lower psi levels generated by an AEG gearbox - not an HPA system (and yes, not factoring in air temperature here may be unfair but, just assuming everything is.. around average or lets a say a warmish day so the propane is actually doing it's thing efficiently).

[Adolf Hamster]

14 minutes ago, Zarrin said:

Yeah this is what I assumed to be the case. Though I thought there would be more too it based on the nature of the propellant gases... could be over thinking it as usual though 😵 

 

 

Okay interesting - it sounds as though I'm missing some core foundation knowledge to fully understand it for myself to be honest and may need to do some further reading. But what you are saying defo helps explain the deficiencies in the propane based gases 👍 

 

What I still don't understand and i don't think is touched on in the above is the correlation between barrel length and it's effect on fps increase in compressed air systems like that of an AEG versus gas (other than ofc the vast difference in percentage increase in barrel length - a pistol's going up by over a 100% and then an AEG maybe getting a 20% boost in length)   

 

I believe I understand the core principle of barrel length to speed/power - taking a real gun as an example, the explosion inside the cartridge propels a bullet forward and while it is being propelled forward through the barrel it is gaining speed, once it leaves the barrel it immediately starts to drop speed, hence a longer barrel gives the projectile more time and length to gain speed.

So the reason an M16 has a higher muzzle velocity than an M4 is that in that extra 5.5 inches of barrel the M16's bullet has continued to speed up, wheres the bullet out of the M4 exited 5.5 inches earlier at a lower velocity.

 

And i do believe you can essentially apply the same principle to an airsoft gun - the nature and source of the propellant being the main difference. The reason (again in my mind) that gas gun's might be more effected than compressed air, is that propane has that fast expansion rate, so that longer barrel may be giving the BB more time to accelerate with a higher rate of expansion behind it from the propane than that of compressed air - and by that i obviously mean the compressed air at the lower psi levels generated by an AEG gearbox - not an HPA system (and yes, not factoring in air temperature here may be unfair but, just assuming everything is.. around average or lets a say a warmish day so the propane is actually doing it's thing efficiently).

 

if you're meaning why don't most aeg's joule creep i'm not 100% but my best theory is that it's due to the difference in the effect of back pressure.

 

assuming that the piston is reasonably lightweight the biggest load it's going to experience is going to be the pressure from shoving the bb out of the barrel, the more pressure it'll slow down (and in so doing will also slow down the bb).  whereas in a gas gun the pressure source is constant regardless of how much resistance it's getting from the bb, i suppose in more scientific terms a spring gun gives the bb a constant energy depending on the spring energy, whereas a gas gun gives the bb a constant force. therefore a longer barrel or heavier bb will extend the bb's time receiving said force thus increasing it's energy.

 

this would also explain why some snipers with heavy pistons can be made to joule creep, where the inertia of the piston is a significant factor in how quickly it can accelerate, needless to say super heavy pistons in aeg's become counter-productive for proper cycling. it also explains the energy drop from short stroking/dsg'ing as by reducing the stroke you're also reducing the stored spring energy, so you need a stronger spring (which for the same level of compression stores more energy)

[Davegolf]

All other variables held constant; the reason Gas systems generate more energy than an AEG or BASR is simply because;

 

As @Adolf Hamster touched on, the 'Gas' turns from liquid in storage to gas, all the while expanding and the floating valve automatically compensates the amount of gas provided for each shot relative to BB weight and barrel length.

 

By that I mean if you loaded a mag with a mix of 0.2 and 0.4g BBs the Gas gun would automatically provide more gas to the heavier BB.

 

This is because the floating valve works on pressure differential, so it KNOWS when the BB has reached the end of the barrel.

(when the BB leaves the barrel there is a massive pressure drop; the floating valve slams forward blocking flow; the bolt is powered back; the gas exit valve is shut off)

 

As the BB accelerates so does the flow of gas behind it, so the BBs speed actually ramps up exponentially (joule creep) - whereas a spring powered gun is using up its compressed air and accelerating the BB in a more 'linear' fashion.

 

This is why volume matching is very important with AEGs and BASRs to maximise performance toward your desired BB weight.

 

HPA is similar to Gas but not automatically compensating, the user has to do this via settings, poppet sizes etc

[Crazy_Crystal]

56 minutes ago, Davegolf said:

As the BB accelerates so does the flow of gas behind it, so the BBs speed actually ramps up exponentially (joule creep) - whereas a spring powered gun is using up its compressed air and accelerating the BB in a more 'linear' fashion.

 

This is why volume matching is very important with AEGs and BASRs to maximise performance toward your desired BB weight.

 

thanks for the explanation Dave.

 

I just thought I'd add that this volume matching is the reason why AEGs don't normally joule creep... the pistons in a lot of shorter rifs will be ported so that only the volume of air required is pushed down the barrel.

(this also should improve accuracy quite a bit due to less turbulent air behind the BB after its left the muzzle but that's another conversation and stops people breaking laws by using super heavy ammo)

 

however spring systems that do joule creep will have a much larger cylinder volume compared to the barrel ratio allowing much more air out the barrel and almost behave like the gas guns... so things like the VSR G-spec (short barrel) and the silverback HTI (insanely huge cylinder) will tend to creep a lot but this allows heavy ammo to be used which is good for a sniper rifle.

 

just a few bits for thought.

[Davegolf]

Tuning and testing of the volume ratio will allow maximum energy to be imparted to your desired BB weight, if done correctly the BB exit should not be turbulent as the pressure should have been 'consumed' by that point and there should not be any excess.

 

With this in mind short guns like MP5K, ARP556 etc are over volumed as standard and as such will joule up heavier BBs well, but this is normally nullified by the barrel shortness and lower FPS, as such limiting their range, and as @Crazy_Crystal said, making for a turbulent exit!

 

Also worth noting a Gas gun can achieve greater joule energy than is ever possible with an AEG or BASR or even HPA due to the expansion.

[Adolf Hamster]

this has turned into quite the debate lol.

 

3 hours ago, Davegolf said:

HPA is similar to Gas but not automatically compensating, the user has to do this via settings, poppet sizes etc

 

i literally had the poppet dwell settings for 0.3 and 0.48g ammo engraved in my stock so i'd remember what to set it to in the field lol.

[E21A]

Short answer to the original question. None 

[Davegolf]

I agree with regard to the 20-30M OP comment.

 

But 30M does not make a field gun in my eyes! I like a min 50M capability.

[Zarrin]

Thank you @Davegolf and @Adolf Hamster some great little nuggets of info in there which I didn't really know or understand before, though am starting to get my head round now 👍

 

I think one of my problems here was not actually properly understanding the nature and factors that cause and effect joule creep. 

[Adolf Hamster]

21 minutes ago, Zarrin said:

I think one of my problems here was not actually properly understanding the nature and factors that cause and effect joule creep. 

 

it's a very misunderstood topic, hell a lot of folk don't even know it's a thing.

 

funny i'm contemplating doing the math now, years ago for a project i measured the spring energy of an aeg and interestingly for a 1j muzzle energy the spring has ~2.5j of mechanical energy.

 

i suspect a lot of that is lost in the gas heating up under compression (as well as the usual leaks/forcing past the hop etc).

 

problem is it's been years since i've done thermodynamics in any great detail so imma have to polish up on it first lol.

[Davegolf]

Crack on lol! My brain isn't that smart!

I just go on applied experience and engineering common sense 😁