.308 20" vs 26" barrel


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jgo296
May 23, 2008, 11:15 PM
im wondering what would you gain in moving from a 20" to a 26" barrel
if it matters the fire arm is a rock river arms lar-308

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Ridgerunner665
May 23, 2008, 11:22 PM
No more than 250 fps or so...22 inches is the optimum length for a 308.

armed85
May 23, 2008, 11:22 PM
Rock River makes a 308 AR-10 now?

Well I don't have any experience with 308 Win. gas operated rifles, but I do know that a longer barrel will give you greater velocity. The shorter barrel would be more handy.

I imagine a 26" barrel on an AR-10 would be quite a handful.

Beagle-zebub
May 23, 2008, 11:27 PM
Six more inches of barrel should lead to it being a lot quieter, too. Muzzle-flash would be diminished, but that might not be an issue in the first place.

jgo296
May 23, 2008, 11:35 PM
besides the length it 2.5 pounds heavier but one is a stainless barrel the other chrome moly
both are advertised a 1moa

jgo296
May 24, 2008, 12:19 AM
ok so if 22"inch is optimal is 2 inches shorter or 4 longer less worse

jmr40
May 24, 2008, 12:28 AM
The .308 is pretty efficient and does pretty well at 20" There have been tests that have shown less than 100fps between 24" and 20". Individual loads and guns will vary of course.

To me 20" is about right for a .308. If I need a longer barrel I want a cartridge with more powder.

taliv
May 24, 2008, 12:42 AM
if you plan to shoot long range and if you're only going to shoot it from a bench or prone, go with the longer barrel.

if it's going to be a 'practical' rifle and you're going to wander around with it on a sling, or shoot from any non-prone, non-bench position, definitely go with the shorter barrel.

2.5lb is a lot of weight. i'll leave you to do the math to see how much 2.5lb feels like on the end of a 20" lever.

one more consideration is that 26" is right on the borderline where people start digging the muzzle in the dirt. high temps, lack of hydration, something else on your mind, a barrel sticking way out past your bag/rest... it'll happen.

Ridgerunner665
May 24, 2008, 12:43 AM
ok so if 22"inch is optimal is 2 inches shorter or 4 longer less worse

That would depend on the powder burn rate...

4 inches longer could very well be worse than 2 inches shorter if the powder used has a faster burn rate...

On the other hand, with slower powders...2 inches shorter could be worse than 4 inches longer...

Confused yet?:)

jgo296
May 24, 2008, 12:46 AM
how much advantage would you expect if you were doing benchrest shooting

Ridgerunner665
May 24, 2008, 12:50 AM
Little to none...the 308 does not need a long barrel.

taliv
May 24, 2008, 12:58 AM
That would depend on the powder burn rate...

4 inches longer could very well be worse than 2 inches shorter if the powder used has a faster burn rate...

On the other hand, with slower powders...2 inches shorter could be worse than 4 inches longer...

Confused yet?

yeah. so what powder have you shot that results in lower MV on a 26" barrel than a 20-22" barrel? or even, what reasonable 308 load in theory would produce those results?


jgo, the longer the barrel, the higher the MV. The higher the MV, the farther your bullet will go before dropping subsonic at which point, accuracy degrades noticeably.

Ridgerunner665
May 24, 2008, 01:12 AM
so what powder have you shot that results in lower MV on a 26" barrel than a 20-22" barrel?
38 grains of AA2495 (very fast powder for a 308) under a 180 bullet gets 2368 fps from my 22 inch barrel...it only gets 2327 from my 24 inch barrel.....when using fast powders...the pressure can and does start dropping before the bullet leaves the barrel...if the barrel is too long...and a 308 does not need a long barrel.

Ridgerunner665
May 24, 2008, 01:19 AM
40 grains of Reloder 15 (a slower powder) gets 2362 fps from the 22 inch barrel...
2412 fps from the 24 inch barrel

Those are with 190 grain bullets.

Ridgerunner665
May 24, 2008, 01:20 AM
Any more stupid questions?

rangerruck
May 24, 2008, 02:06 AM
anywhere from 250 to 300 fps, may not mean much out to 300 yds, but after that, you will see a large diff in the trajectory.

Grump
May 24, 2008, 02:14 AM
ok so if 22"inch is optimal is 2 inches shorter or 4 longer less worse
That would depend on the powder burn rate...

4 inches longer could very well be worse than 2 inches shorter if the powder used has a faster burn rate...

On the other hand, with slower powders...2 inches shorter could be worse than 4 inches longer...

Confused yet?

So, you're asking us to thing about which type of worse is worse?

Unfair.

By the way, I'm more like I am now than I was when I started reading this thread.

Sunray
May 24, 2008, 03:21 AM
"...Any more stupid questions?..." Why does Budweiser think rice belongs in a beer recipe? You asked.
"...There have been tests that have showing..." 100fps loss of velocity per inch of barrel length too.
"...what would you gain in moving from a 20" to a 26" barrel..." Some velocity, but less 'handiness' of the rifle. Every handle an M1A? It has a 22" barrel without a lot of 'handiness'.
IMR4064 with a 165 grain hunting bullet and 168 or 175 grain match bullets. 190 grain bullets work best out of a .300 magnum.

xringer3
May 24, 2008, 05:35 AM
If you're a reloader, you're gonna have to try the different powders and bullets to get your best load. I've got a 700LTR with the 20 inch barrel and was shooting right with the guys with the longer barrel robars at 400 and 500 yards. I've not shot it any further than that. I've taken alot of deer inside 300 with this one and it's very handy.

I once had a short 20inch barrel 243 that after trying different powders, found a load with a 95grain ballistic tip that chronographed an average of 3120fps. The book rated the load at around 3000 and other rifles we tried the same load in with longer barrels wouldn't get as much velocity as my short barrel.

Find the right powder combination with your bullet and you'll get the same velocity or close as the longer barrel in most cases.

jgo296
May 24, 2008, 09:34 AM
ok there doesnt seem to be a decisive answer

what about differences in barrel material stainless vs chrome moly

Ridgerunner665
May 24, 2008, 11:57 AM
Guys...I want to apologize for the "Any more stupid questions" comment...it was late and I was tired...and I get agitated when I sense somebody that is trying to say I don't know what I'm talking about.

I don't know it all, thats true, but I have learned a few things in the past 25 years of reloading and shooting.

Most precision shooters (myself included) prefer stainless barrels...the throat lasts longer.

Ridgerunner665
May 24, 2008, 12:02 PM
Sunray,

190 grain bullets also work really good in a 308 when you are more worried about penetration than trajectory...Like when you are hunting bear in thick cover.

rbernie
May 24, 2008, 01:39 PM
40 grains of Reloder 15 (a slower powder) gets 2362 fps from the 22 inch barrel...
2412 fps from the 24 inch barrel
Twist rate, groove/land configuration, throat condition, fouling, and a myriad of other factors contribute to a given barrel's ability to achieve a certain velocity with a specific load. Unless you're comparing two identical rifles (save for barrel length) from the same production run for the barrel - you're comparing apples to tangerines.

As a general rule, you will continue to gain velocity well past 26" in most any rifle chambering. However, the differences will be diminishing, and in exchange for a longer barrel and incremental velocity gains comes a definite decrease in rifle portability and a very likely decrease in overall accuracy.

Shorter barrels of a given contour from a given manufacturer are GENERALLY more accurate than longer but otherwise identical barrels. Longer barrels from a given manufacturer are GENERALLY faster than shorter ones.

In 308, I have seen experiments that indicated that the return on length past 16" is somewhere between 25fps and 40fps per inch.

Many folk that shoot 308 at extended distances seem to feel that 24" in a heavy contour (for stiffness) is a good length. It's not really useful for offhand shooting, though. For offhand shooting, most folk seem to prefer a 20" barrel and sacrifice a little velocity loss in exchange for better handling in the field.

It all depends on what you want to do.

GarandOwner
May 24, 2008, 01:41 PM
so...22 inches is the optimum length for a 308

20" was tested to be the "best" length for .308, as far as best accuracy goes. (Though you wont see much difference in accuracy between the lengths, especially if you are an average shooter and dont use reloads) The longer barrels average faster velocities thus increasing your range. I assume you are just going to use this for target shooting, so I would recomend the 22"

RugerOldArmy
May 24, 2008, 03:49 PM
I dunno about the advice given in this thread. It seems self evident that if you look to .308 Win in competition, longer barrels are in play. Especially F-Class and Palma.

Wishful thinking?

skinewmexico
May 24, 2008, 03:55 PM
...and a 308 does not need a long barrel.

Odd that all those F Class guys use a 28-30" barrel, when a 20" is best.

Ridgerunner665
May 24, 2008, 04:16 PM
those F Class guys use a 28-30" barrel,

They also use large doses of REALLY slow burning powders (Reloder 19 for example)...so they do need the longer barrels.

H2O MAN
May 24, 2008, 04:41 PM
My favorite and most accurate (sub MOA) M14s have 18.0" barrels ... :)

SlamFire1
May 24, 2008, 05:00 PM
I would consider a 26 barrel on an AR to be quite unwieldy. If perhaps you were shooting it as an iron sighted target rifle, the sight radius would be an advantage, but it still would be long. I use a 24 barrel on my .233 Compass Lake Space Gun.

I recently conducted some load testing. One rifle had a 18 barrel, one a 22 barrel and one a 26 barrel. Nothing in the data below is an exact match across three rifles, it will give you and idea of a comparison.

As I was load developing, I shot Australian ball over the screens as a known load..

When I compare the velocity of Australian ball in the 18 barrel against the 26 barrel, you get about 25 fps additional velocity per inch of barrel. Give or take.

Palma shooters have a weight limit. If they did not have a weight limit some of them would have barrels so long the barrel would have wheels and it would take a crane to emplace. They use the thinnest brass they can find, cram the most powder, and push a 155 as fast as they can. It has to travel 1000 yards.


PTR91 18" barrel


150 gr Australian Ball MF83 headstamp

30 April 2008 T = 75 F

Ave Vel = 2599
Std Dev = 23
ES = 63
High = 2630
Low = 2567
N = 10

M1a 22 Douglas 1:10 six groove


150 gr Hornady FMJBT 43.5 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR
OAL 2.785
18 May 2008 T = 70 F

Ave Vel = 2700
Std Dev = 30
ES = 85
High = 2736
Low = 2651
N = 10

Ruger M77 26 Factory Barrel

150 gr Australian Ball MF83 headstamp

30 April 2008 T = 62 F

Ave Vel = 2819
Std Dev = 19
ES = 64
High = 2859
Low = 2795
N = 10

150 gr Hornady FMJBT 43.5 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR
OAL 2.785
30 April 2008 T = 65 F

Ave Vel = 2756
Std Dev = 28
ES = 97
High = 2806
Low = 2709
N = 10

taliv
May 24, 2008, 05:07 PM
when I sense somebody that is trying to say I don't know what I'm talking about.

i really wasn't trying to agitate you. sorry if my post came across the wrong way. i don't use any powders faster than R15/varget in my 308s so I haven't seen the effects you're talking about. I agree that at some point, obviously, velocity would be reduced, but I am surprised you managed to reach it that quickly. I'm still a little skeptical, to be honest. I'll have to try it at some point when I've got a barrel I don't mind cutting down.

ants
May 24, 2008, 05:32 PM
With the right powder and bullet in .308, the 26" can excel at extended ranges like maybe 600 to 1000 yards.

He said the rifle is a rock river lar308. Is that the right rifle to set up for extended range? Or should he use the lar for 300 yards or less, and build a bolt action rifle for the long shots?

jmr40
May 24, 2008, 05:55 PM
In my opinion the .308 is at it's best as a light handy rifle with a 18"-22" barrel. It is perfectly capable of taking 95% of the game animals hunted in the US at ranges farther than most of us are capable of shooting. It also makes a fine precision rifle for shots out to 300 yards or so. Sure you can put a 3 foot long barrel on it and develop special loads that will make it work at longer ranges, but beyond 500 yards there are better cartridge choices.

Ridgerunner665
May 24, 2008, 05:56 PM
Taliv,

Its not evident is some calibers...243 for example still gets better velocity from slower powders...regardless of barrel length.

I know this because my sons 243 (Remington youth model) has a 20 inch barrel...and I tried every trick in the book to get up to 2800 fps with 100 grain Hornady bullets... I made it to 2780 fps with the bullet seated just off the lands and 44.1 grains of R19.

R15 loaded the same way (forgot the charge, but it was starting to flatten primers) got 2712 fps. Varget = 2730 fps.

But my 308's don't seem to play by these rules.

USSR
May 24, 2008, 06:13 PM
Twist rate, groove/land configuration, throat condition, fouling, and a myriad of other factors contribute to a given barrel's ability to achieve a certain velocity with a specific load. Unless you're comparing two identical rifles (save for barrel length) from the same production run for the barrel - you're comparing apples to tangerines.

As a general rule, you will continue to gain velocity well past 26" in most any rifle chambering.

+1. Barrels vary, even when made by the same manufacturer. For example:

I have two bolt action rifles, both in .30-06 and both with 26" match barrels. With identical loads consisting of 60.0gr of N160 behind a 178gr Amax bullet, the one gets 2950fps, and the other 2875fps. To say that shorter barrels will consistently get higher velocities than longer barrels when a faster powder is used is ludicrous.

Don

Ridgerunner665
May 24, 2008, 07:14 PM
Never mind.

jgo296
May 25, 2008, 08:09 PM
wow i wasnt expecting it to be said that a longer barrel is less accurate
i wouldve thought the opposite

taliv
May 25, 2008, 08:33 PM
did someone say a longer barrel was less accurate? i missed that

armed85
May 25, 2008, 08:55 PM
I'm no expert, but it does make sense that a 20" barrel would be more accurate than a 26" barrel of the same profile. If both barrels are the same and the only difference is the length, the shorter barrel will be more rigid.

There's also barrel harmonics that come into play though that's not a subject I'm very familiar with.

We're talking mechanical accuracy here. I doubt you'll see a practical difference.

rbernie
May 25, 2008, 08:56 PM
If both barrels are the same and the only difference is the length, the shorter barrel will be more rigid.
Exactly.

You can make a long tube accurate, but it requires that you use a very thick profile that renders the rifle unsatisfying for most any offhand work.

Dr. Tad Hussein Winslow
May 25, 2008, 09:54 PM
ok so if 22"inch is optimal is 2 inches shorter or 4 longer less worse

My vote is, 4" longer is "less worse" - i.e. better. I'd rather have the extra velocity - if the gun is high quality, the accuracy difference between 20" and 26" will be miniscule if at all.

But it depends on the use (of course). If lugging it around long distance, the lighter rifle would be a better choice.

atlanticfire
May 25, 2008, 11:20 PM
30" + varget has worked out nice for me.

USSR
May 26, 2008, 08:07 AM
It's the quality of the barrel and the chambering work done by the gunsmith, that will have the most impact on whether a particular barrel shoots well or not. As for the length and contour, let your intended useage determine that.

Don

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