Barrel Length - How Important?

[MagnetoPenguino]

Well, I've read a lot of conflicting information lately. I have a TM P90 that I plan to use as a primary field gun. I know it's often considered an SMG, but I've gone through and M4, a large G3, and a P90, and tried a few others, and I still prefer the P90 for a lot of reasons:

 

1) Sooo user-friendly to take apart, upgrade, and maintain.

2) Bullpup configuration

3) I love the hicaps

4) Ergonomic

5) Two stage trigger

 

So, I figured that if I was going to make it a primary field weapon, I'd have to run an m4 or AK length barrel through the silencer, right? Then I ran into this post, along with a few others on other forums:

 

ome have balked at my (highly customised) APS-2 for the fact that it has a properly crowned 8 inch internal barrel. Only to be shown up in the field by so many a headshot from the very same rifle.

 

Interesting stat, after cutting the stock APS barrel down to almost half its length and properly re-crowning it, my benchrested groupings tightened to a third of what they had been previously.

 

In the 80s, during the height of airgun design and modification, many, many tests were done by fanatical airgunners, many of whom are names you might recognise today, like Theoben. In the high end Airgun world it is generally accepted that on any spring-piston design there is no real improvement after 6.5 inches. Once the round is stable in the barrel, you don't want it in there any longer. The longer its in there the more things like vibration or kinks in the barrel are bound to effect it adversely.

 

So, would I see any advantage to running, say, an M4 or AK47 length tightbore in a silencer over a normal P90 length one? It would be a Dee's custom 6.01 barrel either way. I would probably leave the silencer on most of the time anyway, but being able to take it off would be a nice feature if I don't lose any accuracy or range from being able to do so. It would also have internal upgrades to a bit over forum limits, if that matters.

[terrorist killer]

the p90 barrel is the same size as an m4 barrel,and there is only slight accuracy differential using barrels over 200mm

 

and the P90 isn't an SMG cos it takes 7.62 bullets

[DarkLite]

Longer barrels with the same bore, past 300mm or so, do not have much of an effect on accuracy at all.

 

It is preferable to have a shorter, more well supported barrel - this is a big problem on running barrels through silencers - than a longer one.

 

So I'd say stick with the P90 length barrel, but make sure that your cylinder matches it.

[DarkLite]

the p90 barrel is the same size as an m4 barrel,and there is only slight accuracy differential using barrels over 200mm

 

and the P90 isn't an SMG cos it takes 7.62 bullets

<{POST_SNAPBACK}>

 

Wrong.

 

The M4 barrel is 363mm long, the P90/CAR-15/G36c barrel is 247mm long.

 

Hissing Sid did an exhaustive test a few years back that proved that past 300ish mm it makes no difference.

 

And the P90 is a PDW as well as an SMG since the 5-7 takes the same ammo it can be considered either.

 

And it chambers 5.7mm, fool.

[Aod]

i've found that there's actually little improvement past 250(ish)mm.

 

other than that, spot on.

[MagnetoPenguino]

Alright, thanks.... That's what I was thinking, but I wanted to make sure I made the right decision. I'll just stick with P90 length.

[lewis hiscock]

yeah the difference in accuracy would be neglegable.

[SlvrDragon50]

A tightbore would be more important than barrel length..

[Sledge]

Don't forget hop up. Make sure it's in good condition.

 

[Stealthbomber]

Don't forget hop up. Make sure it's in good condition.

 

<{POST_SNAPBACK}>

Good point...

 

...added to which, a superior design of hop-up is usually worth more than a long-*albatross* barrel.

 

Guns such as the P90, M14, TM G3-series and ICS M4 have a hop-up that allows you to dial in more accurate amounts of hop.

Guns such as the CA M15 and (even worse) the TM MP5, with its poxy lever, have the same range as other guns but, because their hop-up can't be adjusted accurately, tend to go from shooting skyward to shooting into the ground within the space of a tiny movement of the hop-up.

 

A hop-up that allows small adjustments allows you to get MUCH better range out of your gun.

 

On topic, my bone-stock (265fps) TM P90 was already out-shooting CA M15s even before I fitted a 1J spring and a tightbore. Now it wipes the floor with them.

 

At higher powers I suspect a longer barrel helps straighten out inaccuracies caused by poor hop-up. I bet a P90 shooting at 450fps would be just as accurate as an M16 shooting at 450fps.

Equally, I bet an MP5 shooting at 450fps would always be worse, even if you fitted a 500mm barrel, because the hop-up is pathetic to start with.

[GuzziHero]

Strike Chambers. Wonnnnnderful.

[Kama]

the p90 barrel is the same size as an m4 barrel,and there is only slight accuracy differential using barrels over 200mm

 

and the P90 isn't an SMG cos it takes 7.62 bullets

<{POST_SNAPBACK}>

 

As said the p90 fires 5.7 ammo, and a lot of true subemachineguns fires 7.62, ppsh and scorpion for example.

[Sale]

It is still not precisely defined what the optimal barrel length is for accuracy. I would suspect it depends on the power and weight of BBs, so there's no one optimal length. I have a figure of 250-300 mm in my head.

 

The P90 has a 247 mm inner barrel, and it is among the most accurate AEGs by Tokyo Marui. Other infamously accurate guns are the Beta-Spetsnaz, G36C and SIG 552. Is it a coincidence that all of these have around the same barrel length, and most importantly, a wonderful hop-up mechanism?

 

-Sale

[DarkLite]

Good point...

 

...added to which, a superior design of hop-up is usually worth more than a long-*albatross* barrel.

 

Guns such as the P90, M14, TM G3-series and ICS M4 have a hop-up that allows you to dial in more accurate amounts of hop.

Guns such as the CA M15 and (even worse) the TM MP5, with its poxy lever, have the same range as other guns but, because their hop-up can't be adjusted accurately, tend to go from shooting skyward to shooting into the ground within the space of a tiny movement of the hop-up.

 

A hop-up that allows small adjustments allows you to get MUCH better range out of your gun.

 

On topic, my bone-stock (265fps) TM P90 was already out-shooting CA M15s even before I fitted a 1J spring and a tightbore. Now it wipes the floor with them.

 

At higher powers I suspect a longer barrel helps straighten out inaccuracies caused by poor hop-up. I bet a P90 shooting at 450fps would be just as accurate as an M16 shooting at 450fps.

Equally, I bet an MP5 shooting at 450fps would always be worse, even if you fitted a 500mm barrel, because the hop-up is pathetic to start with.

<{POST_SNAPBACK}>

 

This is all true, unfortunately.

 

However, the most important thing to remember (and is also, co-incidentally why most armalites and MP5s have bad accuracy) is that the barrel must be supported well to reduce vibration and movment when the bb is in the barrel.

 

Look at the TM AK and AK-Beta. The inner barrel and hop-up are set VERY solidly into the outterbarrel, which is solid, supports the inner barrel all the way through and mates directly to the hop-up unit. I've seen a AK-Beta shoot more accurately than an M4, even though it's barrel is shorter. Why? Barrel supports.

[lewis hiscock]

As said the p90 fires 5.7 ammo, and a lot of true subemachineguns fires 7.62, ppsh and scorpion for example.

<{POST_SNAPBACK}>

 

that is the 7.62x25mm pistol round ,

not to be confused with the 7.62x39 used in AK47's ect.

 

and the scorpion fires 7.65x17mm

[supportgunner]

So, I gather replacing the barrel on my M249 MKII with a para length would not affect range or accuracy?

 

Also, how do you reduce inner barrel length? Just chop the barrel?

 

Thanks

[SlvrDragon50]

Or replace it entirely

[Aod]

So, I gather replacing the barrel on my M249 MKII with a para length would not affect range or accuracy?

 

Also, how do you reduce inner barrel length? Just chop the barrel?

 

Thanks

<{POST_SNAPBACK}>

chopping the barrel isn't wise. if you leave a burr/don't crown the barrel properly you accuracy will disintegrate.

 

you might bend/dent it while cutting and ruin it that way too.

[lewis hiscock]

although i have succesfully cut down barrels in the past , it is not advisable as depending on the bore , the tolerances for bur and imperfections are very low