16 18 or 20 inch 1:8 barrel choice for accurate 5.56 AR-15 100 - 500 yard rifle

[Linko]

I am purchasing an accurate 5.56 AR-15 Rifle. I am going for accuracy 100 to 500 yds. My choices, all in 1:8 twist are 16, 18 or 20. What are the inherent accuracy gains as I go up from 16 inch?

 

[Linko]

Didnt have any response but, here is mine. I ordered a 16" LaRue .223 POBR cant wait to receive the rifle. All recommendations were 16 will be best for out to 500yds. No need for the longer choices.

 

[DHD]

You are asking about an accurate AR here aren't you? My answer to your question is about that only as I have zero interest in a blasting type rifle as I don't just put rounds down a barrel to blast. I don't know your experience level, so if you already have a lot of time with this type of rifle my post may be of no value.

No sarcasm implied or intended, but how do you know you are purchasing an accurate AR if you haven't shot it yet. I'll say that the LaRue you are purchasing has a very good chance of being an accurate AR as long as you shoot ammo that is compatible. A lot of what makes these rifles accurate is good parts and good assembly. However, you won't see that accuracy if you don't shoot them well. Like a benchrest rifle, only more so.

It can be a very frustrating type of rifle. I have found time and again that you can throw as much money at it as you can afford (and more) and not see huge improvements (think bad marriage to a high maintenance cheating beautiful woman). I have some serious money tied up in 3 different AR's and they all shoot good. There are times they shoot great only to back up that fantastic group with a so so group (same ammo, same conditions, same day, same.......). Groups I am referring to here are under .5 moa then .75 - 1 moa at 600 yards off of a very good rest with wind flags. You have to remember that there is a lot of things going on when you fire these rifles.

As far as barrel length is concerned, I have played with 16", 18", 20", and 24" barrels and every gas tube length except for pistol. They all shot good but I prefer a long gas tube for barrel length (say a mid length gas tube for a 16 " barrel). I would say it's a moot point for you as you are purchasing a 16" and it will have whatever gas tube LaRue puts on it. 16" is a good compact length that is handy to carry.

If I had to pick a barrel length I preferred, I would pick an 18" with a compensator that was not obnoxious. I use a linear type compensator as I don't shoot alone. The bird cage and super duper tactical flash hiders are obnoxious son's of bitâ—‹}~'s.

Long answer to your question, wasn't it. Enjoy your bad marriage to a high maintenance cheating beautiful woman. Hey, it promises to be exciting at the very least.

 

[michael martin]

I am currently developing loads for an AR-15 with a 1 in 8" White Oak varmint style barrel. It is 20 inches long.
Groups, so far at 100 yds., have been from 1.25 inches to .75 inches, all off of an Atlas bi-pod.

Also, keep in mind that these type guns are tactical in nature and accuracy is not at the top of the list.
That is why the only rest I use is the bi-pod which, I believe, gives me a true indication of it's value in terms of accuracy.
Besides. It's fun to shoot.

 

[fm1947]

Linko did you already buy he rifle, stag arms has a model 6 varmint rifle they guarantee 1/2 moa at 100 yards and it will do that and better with your own loads these are 24 inch barrel

 

[Linko]

DHD, you nailed it and I agree on all points, especially the marriage part. No way we can compare the rifles we shoot on this forum and any AR, thats for sure. I had a few of them and sold them to consolidate with one nice one. Appreciate everyones inputs and comments. I also got tired of the adding and changing parts of home built and moderate AR's. Thought to buy just one nice one.

After this I am intrigued with the 20 Practical cartridge. I like the idea of being able to use the 223 brass. Considering a build for that.

My skills shooting and reloading are not ready to graduate beyond my .223 Savage model 12 F TR yet.

And yes asking AR15 question here is odd. But the comments from the members of this forum are not like elswhere. Here they are ACCURATE!

By the way DHD I like your humor.

And funny that you 223rd post was about a .223 AR-15!

 

[Linko]

Linko did you already buy he rifle, stag arms has a model 6 varmint rifle they guarantee 1/2 moa at 100 yards and it will do that and better with your own loads these are 24 inch barrel

Actually that was one of the rifles I sold. It was accurate but just about as heavy as my Savage target rifle. I guess I was looking for something a bit smaller. Was kind of a wierd rifle, like a cross between a heavy bolt action with all the AR moving parts. I liked it but needed a change.

 

[Linko]

I am currently developing loads for an AR-15 with a 1 in 8" White Oak varmint style barrel. It is 20 inches long.
Groups, so far at 100 yds., have been from 1.25 inches to .75 inches, all off of an Atlas bi-pod.

Also, keep in mind that these type guns are tactical in nature and accuracy is not at the top of the list.
That is why the only rest I use is the bi-pod which, I believe, gives me a true indication of it's value in terms of accuracy.
Besides. It's fun to shoot.

Fun to shoot, yep that what this rifle is for.

 

[BoilerUP]

I have a FrankenSPR with 18", 1:8, rifle length gas, HBAR contour BHW barrel. With a DNZ Freedom Reaper 5.66 mount, Weaver GS Tactical 3-10x40 and an empty 20rd Pmag it weighs right at 9lb.

My load is simple: 77gr Nosler CC @ 2.255" COAL over 23.5gr 8208XBR into prepped RP brass stuffed with a CCI-450.

I'll never win a benchrest or service rifle competition with it, but I can put 5 rounds into about 0.6" @ 100yd and 10 rounds into about 0.8" @ 100yd *after* I warm up behind the rifle...gas guns have a learning curve and I'm simply not as comfortable behind it as I am my bolt guns. The rifle gas is very soft shooting compared to a 16" carbine.

When I bulk load (charges thrown with a Lee Perfect Powder Measure into mixed brass), I lose some accuracy but still maintain sub-MOA and don't have any issues hitting a 6" square @ 450yd or a 8" round @ 550yd.

It isn't the most accurate rifle I own, but it is more "fun" and less "work" than most others.

 

[cmillard]

I have an 18" 1-7" twist (Douglas tube) from compass lake engineering. I have shot out to 891 yards with it shooting 77 grain bergers and aa2520. no problem hitting the target whatsoever

 

[DiRTY DOG]

Accuracy difference between 16/18/20 inch barrels? Zero. The 16" will have a little more blast and slightly lower velocity. The 20" will have a little less blast and slightly higher velocity. The difference in velocity between 16/20 inch barrels is not enough to make that a determining factor- you'll need a chronograph to measure the difference and it's effect in the field is less than you'd expect. The 16" is easier to carry and hunt with.

The 18" barrel is more expensive (especially in a factory build) than 16/20 because it has the word "special" attached to it, as in SPR (Special Purpose Rifle). The tactical world believes a 16" is "just" a carbine, but if you add 2" to the barrel and add a scope then suddenly it's a bad@$$ "special" mini sniper rifle. Jump up to 20" and it stops being "special" and just becomes a regular old rifle like thousands of others. The difference between a 16/18 inch barrel or 18/20 inch barrel is just too petty to really discuss. Very very small differences.

More velocity means slightly less drop at 500 yards. If that is actually important to you, skip the 16/20 inch barrels and go 24". Go 24" for a dedicated "target" rifle. I doubt you're that kind of shooter, if you were then you'd know the answer to your question.

In reality, a 16" barely will get you to 500 yards no problem for occasional purpose.

 

[Linko]

Accuracy difference between 16/18/20 inch barrels? Zero. The 16" will have a little more blast and slightly lower velocity. The 20" will have a little less blast and slightly higher velocity. The difference in velocity between 16/20 inch barrels is not enough to make that a determining factor- you'll need a chronograph to measure the difference and it's effect in the field is less than you'd expect. The 16" is easier to carry and hunt with.

The 18" barrel is more expensive (especially in a factory build) than 16/20 because it has the word "special" attached to it, as in SPR (Special Purpose Rifle). The tactical world believes a 16" is "just" a carbine, but if you add 2" to the barrel and add a scope then suddenly it's a bad@$$ "special" mini sniper rifle. Jump up to 20" and it stops being "special" and just becomes a regular old rifle like thousands of others. The difference between a 16/18 inch barrel or 18/20 inch barrel is just too petty to really discuss. Very very small differences.

More velocity means slightly less drop at 500 yards. If that is actually important to you, skip the 16/20 inch barrels and go 24". Go 24" for a dedicated "target" rifle. I doubt you're that kind of shooter, if you were then you'd know the answer to your question.

In reality, a 16" barely will get you to 500 yards no problem for occasional purpose.

You nailed it. It took me a little while to think it thru. I was trying to have just one AR, hence the original question. So yesterday, Instead of the large investment in a "special" rifle and since I have an extra upper I spent a little for a 24" bull barrel and will have a dedicated target upper.

I am not a hunter, just a old guy with a couple of years trying to get as good shooting and reloading for my Savage target rifle as the rifle can out shoot me. The AR project is another part of my love for this sport. Wish I had started this when my eyes were sharp like a hawk.

Thanks for writting all that down. I appreciate.