What is the most accurate barrel length?

[gskrmn]

I have an STG-58 built on an Imbel receiver. I ordered it with the 16" barrel and a muzzle brake. I'm not happy.

The weapon is too loud and the accuracy is unacceptable.

I want to order a replacement barrel. I can have a gunsmith cut the barrel to any length. With a focus on accuracy, what is the optimum barrel length for an STG-58?

[kcsturm]

Check with Brad at Gunthingshe's got some new Chrome lined barrels 21" I think.

What kind of groups are you getting? You can also get a complete bull barrel front-end from DSA that come without the brake.

[gskrmn]

The groups are 6 inches at 100 yards with 147 grain reloads.

With 168 grain reloads, the ammo I use in my M-14 (with 2" groups), the size opens larger.

With Hintenberger ammo the results are even worse.

I'm thinking of order a barrel from DSA and have the threads cut off. It's the barrel length that I want to know about.

[Dano]

Everything else being equal, barrel length has NO effect on accuracy. Barrel length affects velocity, but not accuracy.

A bad barrel is a bad barrel whether its 16" or 21" long.

What you want is a quality barrel regardless of length.

DSA barrels are excellent quality, but so are the original Steyr Mil-spec barrels in new or excellent condition.

Good luck with your choice.

[Farmer from Hell]

It almost sounds like when they cut and attached the MB they buggered it up some how. Because the sight radius doesnt change when you chop the barrel the groups should be about the same as any full length barrel. The velocity will suffer a little. I would take a good long look at the end of your barrel. I get 2-3 inch groups at 100 yds out of my CAI gun.

FfH

[limey]

Which barrel are you looking at $175 or $275

[FALPhil]

Barrel length, per se, has almost nothing to do with accuracy. On guns that have the front sight at the muzzel, barrel length affects sight plane, which for some shooters, allows them to shoot more accurately, but has nothing to do with the physical accuracy of the weapon. On most FALs this is a moot point since the distance between the sights is pretty standard.

Some of the factors which do affect accuracy in a barrel are
- Bore condition (in terms of interior surface)
- Bore uniformity
- Muzzle condition
- Chamber concentricity and alignment with the bore
- Twist rate and bullet length ratio
- Perpendicularity of the bolt face to the axis of the bore.

As long as the barrel is long enough to impart the requisite spin to the bullet, length doesn't matter in terms of accuracy.

Originally posted by gskrmn:
It's the barrel length that I want to know about.

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..Phil
Download free targets at
http://harringt.home.mindspring.com/targets.htm

[Scott S]

Though it won't help with the muzzle blast, you might consider recrowning the barrel. That is if the bore seems OK.

[thorlin]

Removing the muzzle brake might help...

I have two FALs, one with an Entreprise no-rise muzzle brake, one cut/crowned to remove the threads.

Both are of approximately the same rifled length. The shorter one had only 3/4 inch removed to eliminate the threads.

With identical ammo, they both shoot with teh same accuracy, cosistent groups of 2-3 inches at 50yds. I haven't gotten serious about it, I'm not sure if this can be improved.

The braked rifle is MUCH louder. And I feel the blast on my arms/face. Doesn't bother me. I built that one for my brother...it's going to be tough giving it up...

If you cut/crown the barrel to remove the brake, you would certainly lower the noise. You would also now have a clean new crown I imagine that if done properly, this would only help, and would be much cheaper than buying/installing a new barrel.


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Mike Thorlin
Peoria, AZ
STG/R1 - 99%
R1/Blg BBL - 99%
R1A1- 50%

"It hurts where I drilled." ...speaker's identity withheld to protect the stupid.

[Mfg Eng]

I do not believe it is legal to have a barrel shorter than 16" (including permanent muzzle attachment), so cutting & recrowning may not be an option, unless you reattach something to make it 16". Someone please correct me if I'm wrong.

[thorlin]

Originally posted by Mfg Eng:
I do not believe it is legal to have a barrel shorter than 16" (including permanent muzzle attachment), so cutting & recrowning may not be an option, unless you reattach something to make it 16". Someone please correct me if I'm wrong.

You are abslolutely right. I forgot that it was only 16". One could add a barrel extension (permanent). Might be an excellent usage of a sleeved flash hider. No effect but to lengthen the overall length of the barrel. And no blast/noise effects from a brake.

Also, it might be possible to remove the brake (cut welds, desolder, drill pins??) and attach a new one in place of the other. Or a sleeved unit.

??

Mike


[This message has been edited by thorlin (edited November 30, 2000).]

[gskrmn]

Thanks to everyone for all of the excellent input.

Putting this all together I suspect that the muzzle brake installation messed up the barrel crown.

Cutting off the muzzle brake and recrowning the barrel would be a good option but as noted the barrel would be too short at about 15 inches.

I can get a 21 inch replacement barrel. After having the threads cut off and the barrel recrowned it should leave me with about a 20 inch barrel.

If I don't see something on this site that indicates that is the wrong thing to do then that is the way I think I'll go.

Thanks again for all the wonderful information.

[FootLongCuban]

I would clean the gun then take it to the range and shoot a box of Federal National Match or Winchester Ballistic Silvertip. It is important to eliminate ammo as a variable. -FLC

[S.Kargoh]

ever seen that guy on american shooter (television program)?

he shoots a 2 inch snubbie at 1 hundred yards and hits his targets (often balloons). Think his barrel is 'too short' to be accurate?

[Dirtfarmer]

I find that a 100 yd. long barrel is most accurate. ......................................sorry.


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Goodwill,
-Dirtfarmer

[GCF]

Noticed the same thing w/ my STG58. You may want to check (if you haven't already) the side play (wear)on your rear sight. Mine was loose as a goose. Tightened it up by sqeezing, & groups improved dramatically!

Seems to be a pretty common problem. I would like to know if anyone manufactures a high quality replacement. Good luck!

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[New Shot]

Interesting topic. So the only reason my 20" AR is more accurate than my 16" (same manufacturer, same ammo) is that the 20" has a longer sight radius? I always thought it was the barrel length. Learn soemething new everyday.

[Gecko]

Er, maybe I'm a little naive, but why would you crown a barrel in the first place if you are going to add a muzzle break??

[Wadman]

The muzzle brake doesn't touch the bullet. Its inner diameter is much greater than the bore diameter (or at least it should be!). So the muzzle is still the last part of the rifle in physical contact with the bullet as it leaves the barrel. So yes, it had better be crowned.

================================================== =====

Sight radius notwithstanding, a shorter barrel can be more accurate than a longer barrel of the same diameter. Barrels flex and vibrate as a bullet passes through it. A shorter barrel is stiffer than a longer one and vibrates less. This is often referred to as barrel harmonics. When making a barrel shorter is not an option (because of loss of muzzle velocity), manufacturers compensate by making them thicker. This is why you have bull barrels on target rifles. A side benefit of bull barrels, especially with pistols, is that the extra weight serves as added stability.

Some of you may have heard about the BOSS adjustable muzzle brake. The usual way to achieve accuracy was to tune the ammo to the rifle. Some loads generate the right harmonic frequency where the barrel flexes the same way for each shot. If the muzzle is at or very near the same point when the bullet leaves the barrel, your groups should be much smaller. The BOSS system attempts to control the barrel's flexing by allowing you to tune the barrel harmonics to the ammo. This system involves moving a weight (the muzzle brake) forwards and back until you find the "sweet spot" for that particular ammo. Neat stuff, huh?



[This message has been edited by Wadman (edited December 03, 2000).]

[DK]

Originally posted by Dirtfarmer:
I find that a 100 yd. long barrel is most accurate. ......................................sorry.

Yeah, but it gives you those nasty burns on your target!

DK

[DK]

Originally posted by Wadman:

Sight radius notwithstanding, a shorter barrel can be more accurate than a longer barrel of the same diameter.

Interestingly, my Belgian 50.63 w/ 18" barrel is my most accurate FAL. It outshoots my 21" FAL's, and I have gotten 3 shot 1" groups w/ iron sights off a sandbag.

DK


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Historically Freedom is bought with steel, not gold...

[Wadman]

One inch groups? Excellent! What kind of groups were you getting from the 21" rifles though? Admittedly, there could be other factors such as your para model locking up tighter than the other rifles. Either way, that's good bench shooting.

[stimpsonjcat]

Now see here!

all this talk about vibrating barrels has gotten me wondering if I shouldn't cut my 21" down to 18" or so?

Right now I am about to build a R1 kit with a 20" barrel or so. My plan right now is to take both to the range and see who performs better...then whack the other one off to 16.5" or so. Maybe I should consider chopping in increments instead?

I already have the 90 facing and 45 degree chamfer tools to redress cut barrels...so what the heck right?

Gimmee feedback here guys...please!

peace!

[Wadman]

Oh geez, no! If you like the 21" barrel, don't worry about any potential accuracy gain from shortening it. Hell, it's not free floating anyway. If you use the barrel mounted bipod, the whole thing is moot because of the upward pressure you exert on the barrel. Sorry, I should have added that the flexing and vibrating depends on the barrel being allowed to do so. For normally stocked bolt-actions, they (gun writers) always talk about relieving the stock so that a business card will pass between the stock and the barrel.

Personally, I think the 21 inchers are accurate enough and I like the long barrel look. Plus I'd rather have the extra velocity. If you want to make a carbine, go ahead and make it. Don't go through all that work with cutting in increments.

[W.E.G.]

Anybody wanna flail on this a little more?

[FR]

Nope.

[Upside Down @ 100 MPH]

There's an old warehouse down here in Houston where some benchrest shooters used to practice without the effects of wind. They did a lot of testing on a lot of different things. One was optimum barrel length. On their 6PPC's they liked 21.75".

One of the guys also had a hunter class rifle in .308 Winchester, guess what it liked? 21.75"long.

I think there is an article about this in one of the Precision Shooting issues, don't remember which one though.