I have an OBR and an AR-10 with 18 inch barrels.

My SR-25 (long gone) had a 20 inch barrel.

The 18s handle much nicer and dont feel terribly long when you add a suppressor.

The gas system length is longer on 18s and 20s that make them cycle much smoother.

 

On my 6.5 Creedmoor, I installed a 22" heavy barrel on it. It is now a rifle that will only be fired from a bench. It is soooo barrel heavy. That may have to change. Don't make that mistake.

I read a test on long-range accuracy and barrel length with the .308. They started with the barrel at 26" and cut the barrel and tested accuracy at every 1/2" if I remember correctly all the way down to 16". But they determined that the longer barrels only made the slightest difference.

So between 18" and 20". You should probably go with the one that handles better.

 

Yes, I have see a couple of tests like this and the one that stands out in my mind showed anywhere between 20 fps and 75 fps difference per inch of bbl. The shorter you got, the bigger the loss of velocity.

The two 308 rifles that I have now (neither one is an AR) both have a bbl length of 22". I have never fired a 308 with a shorter bbl than that and was wondering what the realistic differences are. Most numbers I have see seem to show an ES of anywhere between 50 and 100 fps for any given load, so I don't think the difference between 18" and 20" is that big in terms of performance, while the difference between 16" and 20" might be.

I have also heard that the shorter you get in bbl length, the louder you get. Not having different length rifles in the same caliber, I have no way of judging that for myself so was wondering what others have seen. Is it really the bbl length, or is it the muzzle break that seem to be more prominent on shorter rifles?

 

What is your objective and or accuracy expectations for this rifle? I get that you mention 500yds or less, but do you expect MOA or under at any distance or can you accept a little more. The 16" AR308's are very handy, and can be quite accurate, but if your expectation is under MOA, you would be better served with a longer heavy barrel. My first AR308 was a 20" heavy bbl and it was just too much of a tank for my liking. I built a 16" with a folding and telescoping stock and it is much more enjoyable to have fun with at the range. I have not put a scope on it, I just use a dot sight. 2" groups are about normal with it at 100 yds. Limited primarily by my sight.I have no issues out to 300yds with it ringing 10" plates. Were I to stretch its legs I would put a good variable on it and I'm certain it would reach out there.

I have never been able to notice a sound difference on a center fire rifle based solely on a couple inches of barrel length. All else being equal. Your choice of muzzle device has more influence.

 

My company says that we will still be getting our annual bonus in July and I am planning on taking some of it and getting a 308 rifle.

I am planning on it being a general purpose rifle, used for pretty much anything from paper to plinking to hunting. I don't ever see myself shooting beyond 500 yards with it, in fact I honestly can't recall the last time I shot beyond 300 yards. My requirement is reliability and sub 2 MOA, although the more accurate it is the better, with a weight of less than 10 lbs - with scope and empty magazine, and obviously the lighter the better.

Right now, I am split between an AR and the M1A Scout. The two distinct benefits of the AR, for me anyway, are the ease of mounting optics and the drop free magazines. I am planning on going with either a combination of a red dot and a traditional 3-9x scope, switching between them as the situation requires, or an LPVO scope. However, if I do end up going with the M1A Scout, I might go with a 2-7x LER scope.

Trying to make sure that I have enough information to be able to make my decision by the time I see that bonus. Otherwise, my wife might decide that I just don't need it and use it for something foolish, like paying bills or something.

 

You will be equally served by either a 16" or 18" in my opinion. Accuracy will be more a result of the quality of the barrel than the 2" difference. Are you planning to build it yourself or Buy off the shelf? If buying off the shelf, what are you considering?

 

I will definitely be buying off the shelf.

If i go with an M1A Scout, it will be Springfield.

If i go with an AR, i need to decide on two things before narrowing down my choice. First is the bbl length, and right now I am leaning towards 18". The second is DI vs short stroke piston vs long stroke piston. I have used both DI and piston in 5.56 and have not found a tremendous amount of difference in performance, although I do not shot any SBR. The biggest difference i find between the two is how much easier it is to clean the BCG on a piston gun. I haven't see many short stroke piston driven ARs in 308, although there are a few. As for the long stroke piston, I have only seen one and it is the PWS Mk 2.

 

I bought a Springfield Armory AR10 and used it when deer hunting back in the fall. It has a 16 inch barrel as well. Accuracy was okay for hunting deer in brushy terrain where most short are under 50 yards. However I found it to be much louder than the 742 Remington 30.06 that I've used for the last 40 years. I'm not sure if it's the shorter barrel or the flash suppresser that Springfield uses that seemingly increased the noise level.

 

I was torn between a 16 and 18 inch barrel when I bought my Windham. Ultimately I settled for the 16 inch barrel and have been well pleased with it's performance. It's not a long range gun but it wasn't bought for that purpose. It does everything I want it to do.

 

22" 6.5cm. Pass on the heavy barrel though. Light or medium cuts are fine.

I've got 556 and 300blk carbines for carbine stuff.

 

Armalite first sold their 24" "T" uppers with Lothar-Walther stainless barrels. Those were some of the finest barrels you could buy at the time. They were heavy but very accurate. I bought one for one of my very first AR10 builds and had it cut and crowned to 20". Still one of the most accurate rifles I own.

200 yds, 10 rounds, FGMM.

They also used those barrels for their SASS rifles. I built a 16" SASS clone with one of their barrels and all Armalite match hardware to go along with it. Rifle shoots .4-.5 moa.

For my 6.5 "AR" build I chose a Ballistic Advantage 22" 5R stainless barrel. I built this for nothing but long range.

Did pretty well for first five rounds (100 yds) Hornady 140 ELD.

 

Lilja 22" SS heavy barrel. :rock:

 

Stainless will always provide the accuracy edge. And makers like Lilja, Criterion, Krieger barrels, etc., will always be the most accurate. Although these barrels aren’t going to hold up in the kind of environment a “battle rifle” is designed for. But when building an AR, decide right away. Are you building a battle rifle? Or are you building a target rifle? You can have a relatively accurate “battle rifle”, although it won’t be nearly as accurate as could be.

Do you want sub-MOA gun that will last & last, and be as tough a piece of gear as you can get? Or do want those 1/4” groups, but knowing that rifle has a service limit? Can’t have both. Anyone thinks they can is fooling themselves.