Pros & Cons of a 16 inch barrel vs. 18 inch barrel for an AR Question?

[Hecktic]

What are some pros & cons of the 16 vs. 18 inch barrel on an AR? I am looking to get an AR in a couple of months and I wanted to know what were some advantages & disadvantages of the 18 inch barrel compared to the standard length of regular ARs.

[SuperSet]

Primarily, the 18" barrel buys you the rifle length gas system, which will feel softer to shoot. Additionally, you'll have a little bit more muzzle velocity and that'll come into play if you are shooting match ammo at smaller targets 300y>.

[BucDan]

Interesting, usually the question is 14.5" vs 16". But it would depend on what you are using it for. If it is just a range gun, the 16 will serve you well. Now if you were benching the gun, then the 18 will work nicely for the FPS.

[BigBamBoo]

The whole FPS loss or gain is really very minimal. I have a 14.5,16,and 18"...and recently sold a 20".

Shooting the same ammo through the three rifles over my chronograph showed a avg. of 35 FPS less with the 16" vs the 18" and a avg. of 90 FPS less with the 14.5".

So as you can see....even the difference between the 18" and 14.5" is not any kind of "deal breaker" IMHO.

Now the difference in handling is night and day with the 14.5" being super handy and fast on target.
Remember that even though the BARREL is a given length, you have anywhere from 1" to 3" extra length depending on your muzzle brake or flash hider your using.

And then there is your gas tube length....this is a non issue with my rifles as all of them has adjustable gas blocs and I "tune" them so they have very slow bolt velocity.

Take care,Stan

[Hecktic]

What is FSP?

[freonr22]

Hav had a 20, 14.5, 16 1/12, 1/7, 1/9 respectively. My future will be a 1/8 18" for my plinking Wish I would have done it sooner.

[gemini1]

The velocity of a 55 gr M193 on a 16" barrel is 3132 fps, the 20" barrel is 3259. So its 127 fps for that 4" difference, which makes it 63.5 fps difference for an 18" barrel.

[motorwerks]

Primarily, the 18" barrel buys you the rifle length gas system, which will feel softer to shoot. Additionally, you'll have a little bit more muzzle velocity and that'll come into play if you are shooting match ammo at smaller targets 300y>.

I feel like I see most in Midlength

[BigBamBoo]

What is FSP?

Not sure what FSP is????....oh...you mean FPS Feet Per Second....the speed that the bullet travels.

The velocity of a 55 gr M193 on a 16" barrel is 3132 fps, the 20" barrel is 3259. So its 127 fps for that 4" difference, which makes it 63.5 fps difference for an 18" barrel.

Are your #'s from shooting over a chronograph or generic tables? The only way to know for sure is shooting over a chronograph. And I have never seen it (bullet speed) linear like your suggesting.

Every load will shoot differently in different rifles due to chamber and barrel specs. Example a slower twist barrel is generally faster then faster twist twist barrel due to friction with a given bullet.

And again with the gas length system...get a ADJUSTABLE GAS BLOCK. Then it does not matter if it is a carbine length or rifle length. And you can tune your rifle to run very efficiently.

Take care,Stan

[reidnez]

What are some pros & cons of the 16 vs. 18 inch barrel on an AR? I am looking to get an AR in a couple of months and I wanted to know what were some advantages & disadvantages of the 18 inch barrel compared to the standard length of regular ARs.

Just to clarify...14.5" is actually standard for a carbine, i.e. military M4 spec. But that means you need a 1.5" (min) muzzle device permanently attached, in order to comply with the minimum legal barrel length of 16". 16" barrels are a little more popular on the commercial market because they allow you to remove or swap out the muzzle device without legal issues.

18" barrels can come with mid-length or rifle-length gas systems; both seem to work fine. Using a rifle-length, the gas port size needs to be a bit larger than it would be with a (M16-standard) 20" barrel.

As for my recommendation, it all depends on your intended use. The difference in performance (as others have noted) is pretty minor. For plinking, carbine classes, etc. I would go with a short barrel, as the longer ones come with a handling penalty and won't give you any benefit <300yds. If you want something to mainly shoot off a rest skip the intermediates and go with a heavy, 20" (or longer) barrel.

[Hecktic]

The velocity of a 55 gr M193 on a 16" barrel is 3132 fps, the 20" barrel is 3259. So its 127 fps for that 4" difference, which makes it 63.5 fps difference for an 18" barrel.

Got it, thanks for the exapmle. I understand fsp better now. I think I'm going to go with the 18' barrel. Does anyone have a good recommendation? I was looking at the Larue PredatAR, the Stag 3g or the Noveske Rouge Hunter.

[Hecktic]

Correction... feet per second

[SuperSet]

You have good taste as those are all excellent. What's the purpose of your build? SHTF/HD, 3-Gun, Precision/High Power, Plinking?
I run 18" Noveskes for my 3-gun uppers and they have been excellent. One even survived a Kaboom and still shoots MOA with 77gr SMKs. White Oak also makes excellent barrels although they don't last as long from my experience.

[Hecktic]

I will definitely consider getting an adjustable gas block. Thanks Stan

[Hecktic]

I’m thinking most of my shooting will be precision/high power & plinking. I will probably put a nice scope on it and use it for distance shooting.