.308 and barrel length


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Monkeybear
March 16, 2008, 03:25 AM
If you were in the market for a HK 91 or other miliary type rifle chambered in .308/7.62 NATO what barrel length would be optimal both in terms of balastics and ergonomics?

I have heard too short a barrel in 7.62 NATO will adversely affect its terminal ballistics. As far as ergonomics consider this a rifle for a guy with multiple rifles and has no bipod, rest or sand bags.

In a nutshell for what barrel length would you want on a 7.62 NATO battle rifle that you may one day have to shoot off hand at Zombies.

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General Geoff
March 16, 2008, 03:28 AM
military style semiauto rifles chambered in 7.62 NATO are never barreled with anything longer than 22" (an M1 Garand rechambered for 7.62 is 24" but I don't count that). Bolt actions, you can sometimes find in 24" or 26". As for ergonomics, it highly depends on what you plan on using the rifle for.

ZombiesAhead
March 16, 2008, 04:02 AM
I was just thinking about this when considering the purchase of an FAL. I was trying to decide between 16.25", 18", and 21".

check out this thread - http://www.thehighroad.org/showthread.php?t=333692

Apparently, you lose 120-140 fps going from 21" to 16.25".

I would have been happy with anything 18"-21" but I went with 21". If you're planning to lug this rifle around a lot, I'm sure an 18" barrel would be a fine compromise.

powermad
March 16, 2008, 04:47 AM
As a FAL fan, 18" is the shortest I would go with a full length gas system.
16" works but looks off balance to me. If I was to have a carbine length one I would have to get a short gas system.

I was going to send mine out to me shortened to 18". But as of right now I am getting 2" groups with it using the irons at 100 yds.
So I think I am gonna leave well enough alone.

Frightener 88
March 16, 2008, 04:50 AM
Is there a functional difforence between 16, 18, and 21? Assuming they all use the same gas system. More to the point...Will the 16" work as reliably as the 21"?

Nightcrawler
March 16, 2008, 05:29 AM
Is there a functional difforence between 16, 18, and 21? Assuming they all use the same gas system. More to the point...Will the 16" work as reliably as the 21"?

On some rifles, the gas port in the barrel has to be widened to allow functioning with a shorter barrel. If you get a conversion done the gunsmith will do this too, if he's doing the conversion properly. Factory 16" carbines (DSA SA-58C, Springfield SOCOM, etc.) have the gas systems tuned already.

This doesn't apply to G3 family rifles, which are not gas operated.

Personally, I don't see a point in going longer than 16" unless you're going to get a full-length barrel and scope the weapon. The velocity difference between the 16.25" DSA carbine and the 17.75" orginal FN Para barrel will be insignificant, and I'm a believer in making your weapons as short as you can. Note that the "Standard" SCAR-H from FN has a 16" or so barrel.

A .308 with a less than 16" barrel is more of a specialized, short-ranged weapon, but even an 11" barreled .308 will offer better ballistics than, say, 7.62x39 out of a standard AK barrel.

Regolith
March 16, 2008, 05:46 AM
I'd say 18-21 inches. Too much shorter, and you lose too much velocity to compensate for the increased handiness, and too much longer and the increased velocity is not enough to compensate for the decreased handiness.

Edit: Personally, I think if you go with a 16" barrel, you're turning it into an intermediate rifle, which is something that the .308 is not suited for. If you want an intermediate rifle, get it in an intermediate cartridge, like the 5.56x45NATO or 7.62x39R.

A longer barrel allows the .308 to do what it does best: work as a full power rifle round capable of hitting hard both at a distance and close up.

Just my opinion.

H2O MAN
March 16, 2008, 09:11 AM
A 16.0" barrel is perfectly acceptable and useful out to about 500 yards if it's done correctly :cool:

http://www.smithenterprise.com/imagesprod/M14K_01_2006.jpg

The M14K will be available in a SAGE stock and LAW483 is working on a synthetic E2 stock for the K gun.

wayne in boca
March 16, 2008, 10:05 AM
The poll does not have a choice for 22",so I was unable to vote.The M14 has a 22" barrel,as John C. Garand intended.

Nightcrawler
March 16, 2008, 03:06 PM
I don't see that an additional 1.5" of barrel (going from the carbine to the para barrel) would make the rifle any more effective. The velocity gain might well be within the standard deviation of a lot of surplus ammo. If you handload (which given .308 ammo prices isn't a bad idea anyway) you can tune the ammo to make the most out of your barrel. A lot of hunters have taken a lot of game with .308 T/C pistols with 14" barrels.

If you want an intermediate rifle, get it in an intermediate cartridge, like the 5.56x45NATO or 7.62x39R

Nah. I've shot steel targets with both types of rifles. .223 makes a "ping". .308 makes a "thwack". If someone was trying to kill me, I'd rather thwack them than ping them, regardless of barrel length.

I think the idea that a .308 rifle needs a long, unweildy barrel to be effective is something of a myth*. As I said, the SCAR-H, going to SOCOM, in its standard "battle rifle" variant has a barrel all of sixteen inches long. Only the "sharpshooter" barrel is longer, and that's only 20". The M110 sniper rifle the Army just adopted sports only a 20" tube, and this weapon is replacing large numbers of M24 SWS rifles in service.

*I have heard, however, that properly stabilizing 175 grain match ammunition for long-ranged shooting requires 18" of barrel. I don't know if this is true or not. For me, personally, it's not an issue; a FAL with an Aimpoint isn't exactly the type of weapon you run a lot of 175grn Gold Medal through. :D

.223 is a LOT more dependent on velocity for effectiveness than .308, and yet people have no trouble chopping it down to sixteen, fourteen, even twelve inches.

Some rifles look/handle better with an 18" barrel, though. The Springfield SOCOM looks funny to me, but the Scout-Squad looks nice. It might come down to which barrel length and weapon you feel fits you best. That's the most important consideration.

H2O MAN
March 16, 2008, 05:22 PM
Nightcrawler
*I have heard, however, that properly stabilizing 175 grain match ammunition for long-ranged shooting requires 18" of barrel.

The SEI CRAZY HORSE® US NAVY MK14 MOD 0 has been credited with a few 800+ yard kills.
All MK14 SEI EBRs have a four land and groove 18.0" medium heavy barrel chambered for M118LR with a 1:10 ROT.

Art Eatman
March 16, 2008, 08:53 PM
Dredging up from memory from back when the .308 first showed up on the scene: It allegedly the first computer-aided design. The goal was to have near-'06 performance but with a shorter barrel. With Ball-C and a 150-grain bullet, some 2,700 ft/sec was achieved from a nineteen-inch barrel. Goal achieved. However, this was done with a chamber pressure of some 55,000 psi, compared to the M2 Ball '06 round's 49,000 psi. (47,000? Disremember.)

Now: With a longer barrel and slower burning powders, better velocities can be had.

Memory. Don't quote me. :)

Art

Frightener 88
March 16, 2008, 10:01 PM
Assuming Im not shooting to 500 yards...Would a 16" FAL carbine work as reliably as an 18" or 21" barrel. I wouldnt attempt to hit anything beyond 300 yards with irons anyway. And as always...Minute of man.

wilson
March 16, 2008, 10:05 PM
I voted 21 I would have voted 20. My m44 does good with a 20 " I just wouldnt go too short.

Nightcrawler
March 16, 2008, 10:09 PM
Assuming Im not shooting to 500 yards...Would a 16" FAL carbine work as reliably as an 18" or 21" barrel. I wouldnt attempt to hit anything beyond 300 yards with irons anyway. And as always...Minute of man.

If you order a DSA 16.25" carbine, it'll work as well as any of their other rifles. You have a choice of a short or a long gas system.

http://www.dsarms.com/images/SA58TAC.gif

http://www.dsarms.com/images/SA58CP.gif

If you take a standard FAL and rebarrel it to 16.25", you may have to drill out the gas port for reliable functioning. On a factory carbine, though, this will already be done. Get the short gas system if you're really worried about it; this supposedly was originally designed to aleviate the problems associated with shortening the barrel, though I think it looks weird.

iamkris
March 16, 2008, 10:27 PM
120-140 fps going from 21" to 16.25".

I used to believe it was around 50 fps per inch. However, I've done tests over a chrono with multiple handloads comparing between a 21" StG58 and a 16.25" Para FAL. From that work, I was seeing around 20 fps per inch for all loads.

If you want max velocity, go 21". If you want max "handiness" but still a good THWACK, go 16". If you want a compromise, go 18".

Alpine Storm
December 4, 2008, 01:50 AM
If you are going for a DMR you really need to have those last few inches. ..308 calibers burn cylender powders which are relatively slow burners. And you need those last few inches. We always used the rule of thumb that you are gaining 100 fps for every inch of barrell beyond 16" out to 24". I may be wrong on that outline, so don't burn me at the stake. But from my reloading experiance, it should be relatively close with some level of variation

The .30 caliber bullets drop fast, about 36" with If I remember right with a factory 30.06 165 gr. at 300 yards. So if you are loosing 400 fps, you are making a 20% reduction. If a carbine is what you want, and you are shooting close, then no big deal.

jpwilly
December 4, 2008, 02:01 AM
If you are going for a DMR you really need to have those last few inches. ..308 calibers burn cylender powders which are relatively slow burners. And you need those last few inches. We always used the rule of thumb that you are gaining 100 fps for every inch of barrell beyond 16" out to 24". I may be wrong on that outline, so don't burn me at the stake. But from my reloading experiance, it should be relatively close with some level of variation

The .30 caliber bullets drop fast, about 36" with If I remember right with a factory 30.06 165 gr. at 300 yards. So if you are loosing 400 fps, you are making a 20% reduction. If a carbine is what you want, and you are shooting close, then no big deal.

Wow, did you read any of the previous posts?

30-06 drops about 13" give or take depending on the load at 300yrds. As previously mentioned the loss in FPS is only around 20fps or so per inch from 22" down to 16"

Browning
December 4, 2008, 12:51 PM
Depending on the load and caliber from what I understand you lose between 25 to 50 FPS for every inch you lose when the barrel is shorter than 22 inches (Source) (http://www.chuckhawks.com/rifle_barrel.htm). However I don't have access to a chronometer, so I haven't been able to confirm this.

The 2001 Edition of the Shooter's Bible states, in the introduction to the Centerfire Rifle Ballistics section, "Barrel length affects velocity, and at various rates depending on the load. As a rule, figure 50 fps per inch of barrel, plus or minus, if your barrel is longer or shorter than 22 inches." But they do not say what category of load to which this 50 fps average pertains.

Jack O'Connor wrote in The Rifle Book that, "The barrel shorter than standard has a velocity loss which averages about 25 foot-seconds for every inch cut off the barrel. Likewise, there is a velocity gain with a longer barrel." He went on to illustrate this using a .30-06 rifle shooting 180 grain bullets as an example, so his estimate was obviously for rifles in that general performance class.


To me for for a semi-auto rifle in .308 Win an 18 to 20 inch barrel is about perfect and it's the right combo where you're rifle is still handy, but where you're not sacrificing a great deal of velocity.

H2O MAN
December 4, 2008, 01:09 PM
It looks like the 16.0" M14K has been put back on the shelves for a few
more years, so I'll stick with the proven MK14s and their 18.0" barrels.

http://www.athenswater.com/images/Mod-1.jpg (http://www.athenswater.com/images/Mod-1_T-1.jpg)

gvnwst
December 4, 2008, 01:11 PM
18" is the best compromise, IMO.

beatcop
December 4, 2008, 01:32 PM
Try a few, you may find that there's a lot less flash and concussion with the standard barrel. That may help your decision out a bit.

Wanta B
December 4, 2008, 07:15 PM
I'd say go 18" for best compromise.If you are looking at getting an FAL then go with the full length gas system if you are considering parts availibility.If that is not a concern than,IMO the 16" short gas system is the handiest and best balanced for fast work.Also might consider the ACE telescoping stock adaptor that does NOT fold as the tele-folder hinge will hit you in the nose if you are not careful.Std length Para stock is good but still need a it of caution shooting southpaw.

I voted 18" but only for best compromise.I think the new SOCOM rifles are going 16" simply do to the current combat enviroment,ie street and h2h.In Africa the 18"Congo NON-folding was the best of both worlds bar none.If I were more urban than 16",more rural than 21".

Bowfishrp
December 4, 2008, 09:40 PM
If you are shooting inside 300 yards then I see nothing wrong with the 16". I have a DPMS LR308AP4 that is 16" and can shoot 300 yards with some hold over....however less than that and it is a killer!

UnTainted
December 5, 2008, 01:53 AM
http://i33.tinypic.com/nyaesi.gif

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