Optimal barrel length for 308

Rotaxpower

Rotaxpower

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I am thinking about getting my barrel shortened on my 700P in 308. The 26" barrel that's on it is a little long for my taste, and was wanting to get it shortened but not sure what length I should go with. What would you guys recommend? I was thinking about 20" or should I go shorter/longer? I also do plan some day to get out to 1000 with it just for fun not competition. Thanks all!
 
The shorter and thicker a barrel is, the less the barrel harmonics will affect grouping, particularly if you vary loads. However, there's a fine line between too short, where you lose velocity for long range and too long. Most powders used for .308 are in the medium burn category so somewhere between 22" and 24" barrel length you reach the point of diminishing returns in muzzle velocity and effects of barrel heating up on barrel harmonics and grouping. Bench rest guys use even 20" barrels but for them very long range shots are not the primary concern. I'd go with a 24".
 
What do you want out of short? I hunt my guns in bush, so short for me means quiet while on the stalk. Because of that, mine is 20inch, though if I did it again, I would go a couple inches short if I could.

If you just want to get rid of some weight, I'd go with 20, like what is on the LTR.

It still makes it at 900m, though I don't shoot that far often.
 
I think 20" is as short as is practical for a long range target gun. With a 20" .308 you should be able to keep most bullets (just) super-sonic at 1000 and for that reason I would not choose to go any shorter. The barrel vibrations, as stated by previous posters, will be less than with your 26" barrel, so in theory at least your rifle might be more accurate.

I went the other way. My .308 wears a 28" barrel, weighs 20 pounds, and is arguably the most accurate rifle I've ever owned.
 
I can hit most the the same nodes with my 22" barrel that I hit with my 26" barrel and my friend's 28" barrel, and velocity is about the same. Unless you're shooting factory ammo, a few inches of barrel length isn't going to make a big difference. The longer barrel can hit higher maximum velocities, but most people shoot at a node and you aren't going to hit the higher ones unless you get into the the 30-32" range.
 
Some of the sniper schools in the US feel they can go as short as 18 with no detrimental effects.Not my idea of fun but apparently works none the less.
 
Shorter is stiffer for a given barrel profile, therefore more accurate but you lose 20fps of velocity for inch of barrel when cutting a barrel.

In short a 18-20 inch barrel work very well at 200-300 yards.
Once 600 yards is reached, you simply need 24" - 26" of barrel.
The extra 6 inches of barrel, gives you an extra 120fps which translates in 50-75 yards more in effective range for hunting and around 9 inches less in wind drift (10 mph crosswind) at 1000 yards.

As a note, M14 have 22 inches barrel are effective at up to 500 yards while both M24 and M40 have 24 inches barrels.

Alex
 
Maybe with factory ammo and equipment from the 1970's...

The statement that you need a 24" to go past 600 yards is laughable.
 
Wow, I guess I will tell my 21" barrel to stop shooting 1000 cause its missing 3-5 inches. I get 2740 fps from my rig, yes its a full custom, but not accurate at all saying you neeeeeeeed 24-26 past 600.
 
I don't like long barrel but they do work better at long range

c4pyro said:
Wow, I guess I will tell my 21" barrel to stop shooting 1000 cause its missing 3-5 inches. I get 2740 fps from my rig, yes its a full custom, but not accurate at all saying you neeeeeeeed 24-26 past 600.
Click to expand...

A 24" is not required at all and won't stop you from getting great results, it's simply "optimal" for 308 Win.
I have a 20" 243 Win which shoot incredibly well at any range but I do lose 180fps in muzzle velocity compared to a 26" barrel and that means a large increase in wind drift and drop at long range.
It's still works very well but the same rifle with 6" more of barrel would be much better.

At any range and for a given barrel profile, shorter barrels (18" - 22") are more accurate and longer barrels (24" - 32") give higher muzzle velocity.
The question becomes is simply becomes what is more important at a given range: pure accuracy or external ballistic performance.

Personally, I'm not a big fan of long barrel because of weight and handling issues and, like most hunters, prefer 20-22" barrels but admit that a long range rifle benefits from a longer 24-26" barrel.

Alex
 
Oh come on c4pyro! Everyone knows that a 308 can't shoot past 800 yards to begin with:

308_traj-1.jpg
 
Longshot said:
Some of the sniper schools in the US feel they can go as short as 18 with no detrimental effects.Not my idea of fun but apparently works none the less.
Click to expand...

Yes, and they can put on a CAN for more fun.

longer barrels usually mean more speed BUT unless to do a whole bunch of tweaking, not much gain past 26"

Shorter barrels do not necessarily mean more accuracy BUT it sure makes it easier to tune

Accuracy at lr has more to do with the bullets tolerance of going subsonic then anything else. Some bullets will, some will not.

If a bullet WILL be stable, then initial muzzle velocity is not that big a deal. Accuracy, and the lack of vertical dispersion will be far more important then another 100fps.

If you go far enough, everything goes subsonic.

My tactical 223 Savage wears a 22" barrel. I like the compact size and have no issue chasing 338 LM's out beyond 1400yds.

My F TR's use 28" barrel and are loaded to the 'nth degree. I get some really exciting speeds AND accuracy.

Jerry
 
AlexF said:
A 24" is not required at all and won't stop you from getting great results, it's simply "optimal" for 308 Win.
I have a 20" 243 Win which shoot incredibly well at any range but I do lose 180fps in muzzle velocity compared to a 26" barrel and that means a large increase in wind drift and drop at long range.
It's still works very well but the same rifle with 6" more of barrel would be much better.

At any range and for a given barrel profile, shorter barrels (18" - 22") are more accurate and longer barrels (24" - 32") give higher muzzle velocity.
The question becomes is simply becomes what is more important at a given range: pure accuracy or external ballistic performance.

Personally, I'm not a big fan of long barrel because of weight and handling issues and, like most hunters, prefer 20-22" barrels but admit that a long range rifle benefits from a longer 24-26" barrel.

Alex
Click to expand...

There was a REALLY smart group of guys who did some really exhaustive testing of optimal barrel length for the 308 in Houston Texas back in the 70s who conclusively deduced that the optimal length for 308 Win in a bolt rifle was 21.75 inches. They determined that anything longer was only going to enhance sight radius on iron sighted rifles.
I have been with C4Pyro and several others at a shooMystic put on a few years ago and the bunch of us who were shooting 308s had NO problem with consistant extreme accuracy at 1400 yards.
IIRC Black Cloud put something in the area of 23 shots at clay birds before missing 1 at beyond 1000 yards.
I have video of C4 shooting a 4" gong at 1100 yards.

Sorry Alex, but you DON"T need a long barrel to make a 308 WORK at real long range distances.
 
I quite like my 24" barrel on my Rem M700 Varmint SPS because I can use the same cleaning rod for all my other short (18.5" and 22") barrel rifles! :D

That rundown in Match 67 (?) of DCRA's NSCC matches; I believe makes me grateful my barrels are only 24". For those of you who don't know Match 67, it's a 500m to 400m mound rundown to knock down 8 x 12" square steel plates with only 5 rounds each for you and your spotter. One of you runs with the rifle and the other carries the spotting scope. YEEEhA! :D

Go with what works for you and your game (also yer budget! ) ....

Cheers mates!

Barney
 
alberta tactical rifle said:
There was a REALLY smart group of guys who did some really exhaustive testing of optimal barrel length for the 308 in Houston Texas back in the 70s who conclusively deduced that the optimal length for 308 Win in a bolt rifle was 21.75 inches. They determined that anything longer was only going to enhance sight radius on iron sighted rifles.
I have been with C4Pyro and several others at a shooMystic put on a few years ago and the bunch of us who were shooting 308s had NO problem with consistant extreme accuracy at 1400 yards.
IIRC Black Cloud put something in the area of 23 shots at clay birds before missing 1 at beyond 1000 yards.
I have video of C4 shooting a 4" gong at 1100 yards.

Sorry Alex, but you DON"T need a long barrel to make a 308 WORK at real long range distances.
Click to expand...

Good evening, let me start by saying that I'm honored to have an expert from Alberta Tactical Rifle reply to one of my posts even if it's to confirm that I'm wrong.
I do agree with the point that you don't need a long barrel for 308 to work well but the question is: what is the optimal length?
Can a shooter with a 21.75" barrel outshoot himself with a, say, 26" barrel?

Luckily at least one experimental answer is easy to find: look at what barrel length wins in world class F-TR competitions (I don't know the answer but will look it up).
The optimal barrel length has to be the median or average winning barrel length (or there is some hidden bias, always a possibility).

Regards,
Alex
 
Here is an article about the Houston warehouse: http://www.angelfire.com/ma3/max357/houston.html

The 21.75" figure was supposedly optimal for accuracy, not velocity. There is no such thing as "optimal length" as far as velocity goes, and there is no fixed value for velocity loss per inch. Both of these are highly dependent on the caliber and cartridge, in addition to the bullet and powder combination being used.

I chopped one of my 308 barrels from 26" down to 22". I only lost 20 fps. on my 190 SMK + 42.3 gr. Varget load, but a whopping 200 fps. on my 110 VMAX + 48.0 gr. Varget load. Why? Because the load with the heavier bullet had less powder and it was running at a higher pressure than the load with the lighter bullet. The burn was nearly complete in the 22" barrel, but it wasn't for the lighter bullet load. Similarly, take two loads with the same bullet running at the same velocity, but using powders with very different burn rates and start chopping down the barrel. The load with the faster burning powder will maintain most of it's velocity down to a shorter length than the load with the slower burning powder. It requires less barrel length for a complete burn. This idea that a 24" 308 barrel is required for long range is decades old and was based on the bullets and powders available at the time. It's probably based on a single load. Technology has changed, we have more efficient powders and bullets with higher BCs.

Talk to a bunch of guys shooting 155's with Varget and ask them what their velocities are. The answer will most likely be somewhere between 2800-2950 fps. and where they are on that scale isn't proportional to their barrel length at all. You'll usually only get velocities over 3000 fps. from Palma guys running a 30-32" tube. Guys shooting the 175 SMK will give you a velocity between 2600-2750 most of the time, again with no relation whatsoever to barrel length. When you ask them why they shoot it at that velocity, the answer is almost always: "well, I can run it up to X fps., but it shoots much better down here at Y fps.". And Y fps. is obtainable whether you're running 20" barrel or a 28" barrel. This guy was winning the US F-Class Nationals shooting the 175 SMK at 2610 fps.: http://www.6mmbr.com/gunweek031.html You can easily hit that node with a 20" barrel. What F-Class barrel lengths are winning is irrelevant. Most people are getting longer barrels because they've always been told that they need a long barrel to be competitive. Then they run them at nodes that you can hit with shorter, stiffer barrels...

A few inches of barrel length has a lot more effect when you're using factory ammo, not as much with handloads since you tend to tune them to nodes vs. running the same charge weight for every gun.
 
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