Barrel Length

[Slade xTekno]

I have been paintballing [mostly pump] for over 5 years, a sport in which barrel you choose to use can make a big difference. In paintball, if two unported barrels of identical quality and different lengths were used to fire two identical paintballs at 300fps,

-the accuracy would be the same due to their identical quality.

-the range would be the same because paintball begin to decelerate immediately after leaving the barrel and all objects of equal mass decelerate at the same rate.

-the amount of air needed to propel the ball out of the barrel would be different, as the paintball would have more length to accelerate.

The conditions are theoretical, but the results I have observed in practice.

 

Looking at airsoft, I was wondering if barrel selection is as important. If two barrels of identical quality and different lengths [ie a Prometheus Tightbore for the AUG and MP5] were used to fire two identical 6mm BBs at 1J out of guns using the exact same gearbox, motor, and battery,

-wouldn't the accuracy be the same due to identical quality?

-wouldn't the range be the same due to the fact BBs begin to decelerate immediately after leaving the barrel and all objects of equal mass decelerate at the same rate?

-wouldn't the fps of the shorter barrel be slightly lower due to the smaller length the BB has to accelerate with the identical energy used to propel it?

[stuka]

Hmm I see what your asking about, but personally I think that the accuracy would be different with the different length barrels heres my theory:

When the BB is fired it doesnt go in a straigth line but bounces around within the barrel thats why tightbores make a shot more accurate as it has less space to bounce around, so as the barrel gets longer the bouncing reduces meaning the shot becomes more stable and accurate(AUG Barrel), whereas the MP5 barrel is shorter so has not had enough time to stabilise so is less accurate because of the shorter barrel.

 

Just my thoughts and theory....

[Badly Browned]

Well, with hop up, the BB actually rolls out of the barrel. I always thought the tightbores helped with the air. The smaller barrels makes it so more air is there to push on the BB, which is why you see an increase of 8 or so FPS when you install a tightbore. I am not sure about shot groupings though, I bet its not too much a difference though since you do not get very long ranges in airsoft anyways.

[Sledge]

Any chance we could get Hissing Sid and some other people who've tested the theories in on this? Only I'm seeing a lot of speculation already.

 

*Fires up the Sid Signal*

 

[Badly Browned]

Any chance we could get Hissing Sid and some other people who've tested the theories in on this? Only I'm seeing a lot of speculation already.

 

*Fires up the Sid Signal*

 

<{POST_SNAPBACK}>

 

Hehehe, yeah, we need someone who ahs actually tested these, otherwise its just a thread with a bunch of guessers.

[Sledge]

Thing is, whilst it should be possible to work things out on paper, the real world has a nasty habit of doing the unexpected. Also, the last time I quoted one of Sid's posts on this subject, it triggered a shitstorm, so I'll let the man himself comment if he wants to. I'll keep me head down.

*Engages cloaking device*

 

[tmas]

This was actually my first question when I registered on Arnies (mid December) and it ended up being a 5 page thread.

[Sale]

Looking at airsoft, I was wondering if barrel selection is as important.  If two barrels of identical quality and different lengths [ie a Prometheus Tightbore for the AUG and MP5] were used to fire two identical 6mm BBs at 1J out of guns using the exact same gearbox, motor, and battery,

-wouldn't the accuracy be the same due to identical quality? 

-wouldn't the range be the same due to the fact BBs begin to decelerate immediately after leaving the barrel and all objects of equal mass decelerate at the same rate? 

-wouldn't the fps of the shorter barrel be slightly lower due to the smaller length the BB has to accelerate with the identical energy used to propel it?

<{POST_SNAPBACK}>

1) Most likely yes.

2) In practice, definitely yes.

3) Yes.

 

We haven't figured out exact border values for optimal barrel length, because the benefit of such knowledge is minimal compared to the extreme amount of testing it would require. There are so many different factors that I can only say a few guidelines and rules of thumb.

 

As with real guns, a very short barrel will not be as accurate as a very long barrel. We're talking like 10-15 cm lengths here. However, increasing barrel length will increase accuracy only to a certain point. If someone seriously says a 2 metre barrel will be more accurate than a 50 cm barrel, we can stop discussing right away.

 

So what is the optimal length? We have to disregard realsteel info here, because rifles usually have long barrels to give the bullet a high muzzle velocity. Tests by Hissing Sid and a few of my team mates along with my personal observations have shown that around 20-25 cm the barrel of an airsoft gun will be as accurate as it can get. I'll compare 247 mm Prometheus and KM barrels and a 363 mm Prometheus barrel in may. If I notice anything wild, I'll let you all know.

 

Even if we assume that the barrel is perfect quality and always sends the BB's exactly to the same trajectory, even a slight wind will make the possible difference in accuracy marginal. What good is a theoretical 0 mm grouping compared to a 25 mm grouping when imperfections in BB's and wind might throw the BB's off over 250 mm? All numbers are only examples.

 

The difference in muzzle velocity is easy to compensate with other parts, and skirmish limits are usually so low that they are easy to reach no matter what kind of barrel you have.

 

-Sale

[Hissing_Sid]

Any chance we could get Hissing Sid and some other people who've tested the theories in on this? Only I'm seeing a lot of speculation already.

 

*Fires up the Sid Signal*

 

<{POST_SNAPBACK}>

Just what I've been looking forward to:- Another opportunity to be forced to defend myself against a bunch of pricks with nothing better to do than try to justify owning guns with stupidly long barrels because they have small penises.

 

So, anyway....

 

First thing is that a longer, or tighter, barrel will increase power - to a point.

 

If you take, for example, an MP5, and bung a tighter barrel in it then the power will go up, but only slightly. If you fit a longer barrel on it then you will increase the power proportionally until such time as the cylinder runs out of puff and the BB will then begin to slow down before it exits the barrel.

 

So, the first thing to understand is that if you take 2 identical guns and bung a tightbore or longer barrel on one you will immediately see a small increase in power compared to the stock gun.

 

Let's say you have two guns with the same muzzle energy and one has atightbore and the other doesn't. What can you expect?

Well, when you shoot the gun the BB hits the hop-up and flips up and actually scuttles along the top of the barrel as it moves along it. Try this for yourself. Colour a bunch of BBs with felt pen. Fire them. See where the felt pen line is inside the barrel. It'll be along the top.

 

Now, I'm only guessing but I suspect that the real difference between a normal barrel and a tightbore is simply that the BB can't yaw so much as it travels along it.

Imagine rolling a tennis ball down a drain-pipe and it'll come out rolling in a pretty straight line.

Roll a tennis ball down a 24" diameter pipe and it gets chance to zig-zag as it rolls and it's more likely to come out rolling at an angle to the pipe when it exits.

 

There's other stuff to consider too.

On a gun with a long barrel you use an unvented cylinder. This has the maximum possible volume to accelerate the BB along the barrel.

The issue is that the piston accelerates from zero and, as it does, the BB moves along the barrel and through the hop up - as soon as the piston starts moving.

On a gun with a shorter barrel the cylinder has vents. This means that the piston travels forward, the BB stays still and the air is pushed out of the vents until the piston passes them. Once that happens the BB can start to move. The piston is already moving at high speed so the BB will accelerate much faster.

 

You can try this for yourselves too kids. Take an MP5K and chrono it. Now take it apart and cover the cylinder vents with sticky tape. Now try shooting it.

You should find it's shooting about 10fps lower with the unvented cylinder.

Also, remember this cos it'll be important later (if I remember).

 

Anyway, point being that the BB is going slower as it passes the hop-up in a long barrelled gun than it is in a short barrelled gun.

So what?

I dunno.

I expect this means that you get a sharper hop-up on guns with vented pistons and a softer hop-up on guns with unvented pistons.

Of course, this is all kind of irrelavent since the user will just adjust the hop to whatever is required to make the BB fly straight.

On some small level I bet that guns with vented cylinders probably use less hop than guns with unvented cylinders.

Never tested that though so it's just speculation.

 

So what have I checked?

 

Well, I got myself a stock Marui P90 and tweaked it so it is giving about 1J energy. I used a P90 cos it's very easy to swap the barrels out.

I'd already tweaked it and knew it was shooting at 1J so I had a baseline figure for comparison with future results.

I fitted the gun with an unvented cylinder so that it'd have enough puff to propel the BB through the longest barrel I planned to test.

 

Remember I said about it being important that the MP5K power decreased when used with an unvented cylinder?

 

So, after I fitted the unvented cylinder in the P90 I tested it again and found that the power was still 1J.

This is important cos it means that a BB isn't travelling at full speed when it gets shot out of an MP5K barrel but it has reached full speed by the time it gets shot out of a P90 barrel.

Again, this fact will become important later for reasons which will become apparent.

 

Anyway, on a day when I was bored I gathered up a whole pile of barrels that people had been foolish enough to leave at my house or which I had lying around. I also gathered up 2 mates to do the testing with me, to try to avoid subjective results. I've posted the results of the tests I did elsewhere so, suffice to say, there was no practical difference in accuracy between any of the barrels I tested, ranging from a P90 barrel to an M16 barrel (IIRC).

When I chronoed the gun with each barrel there was a small power increase from the longer barrels, just as you'd expect.

The stock P90 was firing at 325FPS and, when fitted with the longest barrel, it was firing about 10FPS higher thn that.

 

Next I tested tightbore barrels. I happen to have a whole bunch of 460mm G3 barrels so I was able to test similar barrels. I wasn't testing an MP5K 6.03 barrel against a 6.04 M16 barrel. They were all G3 barrels. I had (again IIRC) a Systema brass 6.04, a KM TN 6.04, a stock Marui Brass 6.08, a TK twist barrel and a Prometheus 6.03.

Everything went as you'd expect. The tighter the barrel the better the groups. The only oddity was the TK twist barrel. That would score some good groups and then just lose it completely for a few shots.

At 20m The 6.03 could shoot almost through the same hole. The 6.04s were shooting 1" groups. The Marui barrel was shooting 3" groups and the TK barrel would put 3 or 4 shots through the same hole then put another 2 into the wall 3ft to the side of the target.

What about power?

The stock barrel was shooting about 330fps. The 6.04s were shooting about 332-333 and the 6.03 was shooting about 333-334. A small difference but a repeatable, definate one. The TK barrel was, alas, shooting way down at about 315.

I suppose it's possible that the TK barrel would have blossomed into a beautiful butterfly if I'd fettled the gun to increase the power back up to 330fps but, pah. Life's too short.

 

So, you're saying that you tested a bunch of barrels and they were all just as accurate as each other?

Uh huh.

 

Aha! You're saying that a 5cm barrel is as accurate as a 50cm barrel. That's nonsense!!!

Erm, I didn't say that at all. I said that I tested a bunch of barrels ranging from a stock P90 barrel to an M16 barrel and there was no noticeable difference.

 

Remember I said it was important the MP5K was affected by different cylinders but the P90 wasn't?

Here's what I think, and it's pure speculation:-

I think that it's important to see that the MP5k barrel was so short that the BB didn't get chance to accelerate fully when the unvented cylinder was fitted.

I think that it's important that the BB did accelerate fully (irrespective of cylinders) in the P90 length barrel.

I think that once you've got a barrel as long as a P90 one then you don't need to worry about any of this stuff cos, at that length, the BB starts to do the same thing inside every barrel.

In short, unless you've got a stupidly short barrel, such as an MP5k, then barrel length makes no difference. Unless you've got a tiny penis.

 

Anyway, that's how it all works out in my little head.

I try to explain my methods and justify my conclusions. Now watch as a bunch of muppets show up and say "Joo suxx0rz!!! Long barr3lz r00lz!!!"

 

[edit]

Oh, Sale nailed a couple of points I forgot about but there was one other thing I meant to suggest.

BBs are not exactly marvels of engineering.

I think it'd make an interesting test to shoot 500 BBs (into a foam target) and put all the ones you perceived to be "accurate" in one dish and all the ones you perceived to be "flyers" into another dish.

Having done that, it'd be interesting to take all the "accurate" ones and shoot them again.

I wonder if they would all be accurate or if you'd still end up with some of the supposedly accurate BBs being flyers?

That experiment would show if flyers are poorly made BBs or inconsistancies in the operation of the gun.

Frankly, I've got better things to do.

 

also, for anybody with a deep masochistic streak, HERE'S the other part of this thing.

[Sledge]

joo sux. i put a psg1 barel on mi glock 18 aep and now it does 560fps and can shoot 3 miles

 

Or something. But now to await the flaming muppets.

*Turns off Sid Signal, and waits for random people to argue*

 

[Catman]

joo sux. i put a psg1 barel on mi glock 18 aep and now it does 560fps and can shoot 3 miles

 

Or something. But now to await the flaming muppets.

*Turns off Sid Signal, and waits for random people to argue*

 

<{POST_SNAPBACK}>

 

Lots of room in your pocket then

[snorkelman]

course theres always the view that for an average shot the simple process of laying out 50 clams for a better barrel could well encourage them to make a bit more effort at improving stance aim etc and actually acheiving a more consistent grouping

 

the money out their pocket concentrating their mind

[staticzero]

-a bunch of neat words-

<{POST_SNAPBACK}>

AH, I am so happy you got to this thread first. I sure didn't want to spend my evening writing all that. Bravo!

 

 

I'd like to add that, based on my own experience (I have Prometheus tightbores in six of my guns and have used other brands as well), in terms of accuracy so much more can be done to improve the shooter than the gun in airsoft. While I've seen a change in accuracy after switching to a tightbore in a given gun it's only really noticeable in an ideal, controlled situation rather than in a practical skirmish situation. There are probably far better things to spend money on than a tightbore in most cases.

[onizuka-gto]

AH, I am so happy you got to this thread first. I sure didn't want to spend my evening writing all that. Bravo!

I'd like to add that, based on my own experience (I have Prometheus tightbores in six of my guns and have used other brands as well), in terms of accuracy so much more can be done to improve the shooter than the gun in airsoft. While I've seen a change in accuracy after switching to a tightbore in a given gun it's only really noticeable in an ideal, controlled situation rather than in a practical skirmish situation. There are probably far better things to spend money on than a tightbore in most cases.

<{POST_SNAPBACK}>

 

ok, im confused now, someone said the best thing to do is increase your FPS cos harder is better, but then someone did some test, and said actually, getting a tightbore is a better upgrade, cos higher fps means a faster lost of speed at longer range, so accuracy is more ideal, but now you say tightbore isn;t worth the upgrade...so.....what is the best or most worth while upgrade we should think about first?

[Hissing_Sid]

I'm sorry.

 

I don't see where I've made any comparison between power and accuracy.

All I've done is compare barrels of differing lengths.

 

Depends on what the gun is for.

If it's an all-rounder then bung a spring and bushes in it to set it at 1J then begin to tune the guns accuracy.

If it's a CQB gun then it may well already be shooting near the limit for CQB (maybe 300fps) in which case you can move straight to the stuff which improves accuracy.

 

Still confused?

[onizuka-gto]

I'm sorry.

 

I don't see where I've made any comparison between power and accuracy.

All I've done is compare barrels of differing lengths.

 

Depends on what the gun is for.

If it's an all-rounder then bung a spring and bushes in it to set it at 1J then begin to tune the guns accuracy.

If it's a CQB gun then  it may well already be shooting near the limit for CQB (maybe 300fps) in which case you can move straight to the stuff which improves accuracy.

 

Still confused?

<{POST_SNAPBACK}>

 

 

ok. I think i get the idea. i think.

 

But i have to ask one more question, sorry if i sound like an idiot.

 

When you mention "then begin to tune the guns accuracy." what does that enticle?

 

If i upgrade an all-rounder weapon to 1J already i.e. change springs, gear box/cylinder, what else do i have put in, to "tune the guns accuracy"?

Besides improving my aim.

[ChiefLouk]

ok. I think i get the idea. i think.

 

But i have to ask one more question, sorry if i sound like an idiot. 

 

When you mention "then begin to tune the guns accuracy." what does that enticle?

 

If i upgrade an all-rounder weapon to 1J already i.e. change springs, gear box/cylinder, what else do i have put in, to "tune the guns accuracy"?

Besides improving my aim. 

<{POST_SNAPBACK}>

A tightbore and new hop-up bucking are about all you can do in most guns.

[onizuka-gto]

Thanks! And here i was thinking of putting a tightbore 400mm extended barrel into my newly expected MP7A1 because:

 

"Obivously The world of America Forum with gazillion user says, agrees , no, duh, commonsense, everyone knows a longer barrel is more accurate stfu its the FTW cos I say so and it's true for Real steel so it ust be true for Airsoft, n00b!".

 

I'm glad i found some real advice that applies to Airsoft weapons ONLY.

 

[ChiefLouk]

Thanks! And here i was thinking of putting a tightbore 400mm extended barrel into my newly expected MP7A1 because:

 

"Obivously The world of America Forum with gazillion user says, agrees , no, duh, commonsense, everyone knows a longer barrel is more accurate stfu its the FTW cos I say so and it's true for Real steel so it ust be true for Airsoft, n00b!".

 

I'm glad i found some real advice that applies to Airsoft weapons ONLY.

 

<{POST_SNAPBACK}>

Not all Americans are like that, but there are a lot of them.

 

I am someone that actually tries to help those who try to help themselves.

[Sale]

If you get variance in muzzle velocity, the gun won't be as accurate as it can be. Pneumatic parts may improve accuracy in this case. They are the nozzle, cylinder head, cylinder and piston head.

 

-Sale

[Hissing_Sid]

If you get variance in muzzle velocity, the gun won't be as accurate as it can be. Pneumatic parts may improve accuracy in this case. They are the nozzle, cylinder head, cylinder and piston head.

 

-Sale

<{POST_SNAPBACK}>

Absolutely.

 

Repeatibility is the key to accuracy. It doesn't matter if your barrel has a U-shaped bend in it. If the gun will put BBs on the same spot, time after time, then the gun can be said to be accurate.

 

OTOH, if your air nozzle doesn't quite fit into the hop-up every time then some of your shots will fall short and some of them won't. In this case, even if some of your shots are on target the gun can't be considered "accurate".

 

Which, in un-related news, is why my KJW M700 is the worst sniper rifle in the world.

[Redox]

Its skarclaw on my brothers account.

 

A few weeks back I had the opputunity to compare a non tightbore gun with a tightbore gun, the tightbore was a 6.04.

 

The only difference the tightbore made was less discrepancys, so less bbs would be off the rough group you have. (In terms of accuracy)

 

I would buy other things with the money myself.

[Aod]

just a thing to Add, if you have a Cylinder meant for a short barreled gun (MP5 for example) and then you have a 500mm barrel (or something) which is about 5times as long as it should be for the Cylinder, you'll also lose FPS, this is due to there being a set amount of air-compression size in the cylinder, and this is then matched (roughly) to the barrel

 

if the barrel is to long, eventually the pressure infront of the bb will be greater then behind it and it will decellerate rapidly while still within the barrel (eek).

 

moral of the story, always match cylinder type to barrel size.

 

btw, can someone furnish me with the inner diameter/radius of a Cylinder?

[lewis hiscock]

if the air nozzle wasnt fitting into the hop unit wouldnt it create a snap like noise and genrally damage the nozzle?

[Sale]

if the air nozzle wasnt fitting into the hop unit wouldnt it create a snap like noise and genrally damage the nozzle?

<{POST_SNAPBACK}>

No, because it's pushed forward with a relatively weak spring. A poor fit will only cause loss of pressure, which may vary from shot to shot.