Cutting a 20" AR barrel back to 16"

[Precision40]

Is the bolt-face to gas-hole distance on an AR barrel the same on a 20" as it would be on a Mid-length or CAR? I have a 20" barrel that I'm thinking about having cut back to 16" and would rather not find out the hard way you can't.

[GentlemanJim]

No three different spacings

And a 16" barrel with rifle gas is kinda iffy

Jim

[M ammo]

I have a 16 in barrel, it works, well, I have a pig tail gas tube on it as well.

BUT when it comes time to get a new barrel I'll go with a 20"

The reason is powder burn rate. With a 16 in barrel I can only get the bullet going so fast, no matter what powder I use, or how much I put in.

I have shot all kinds of 3 Gun matches, and the extra 4 inches, is not going to hurt your maneuverability in enough situations to worry about.

Being able to get your rounds FPS to 3200,, will be more of a help than the short barrel maneuverability advantage.

Just my opinion.

Jim M ammo

[Aircooled6racer]

Hello: If you feel you need to cut it then cut it to 18". Thanks, Eric

[Charles Bond]

Hello: If you feel you need to cut it then cut it to 18". Thanks, Eric

I agree that this is much better advice than cutting it back to 16 inches. Still better is sell your 20 inch barrel and buy a 16 if that is what you want. Lately 16 inch barrels are easy to find but 20s are on back order. Depending on a number of factors, you might find someone who will just swap.

[BPiatt]

I've been running a 16" barrel with a long gas system for a long time. They will run just fine.... however, when changing from a 20" to a 16" you might have to enlarge the gas hole a touch. No big deal just keep in mind that the bullet dwell time between gas port and muzzle is now shorter and may affect cycling.

I've always been fond of the feel of the long gas system. Carbine barrels kick harder and exert higher pressures at the bolt.

DPMS sells the Tactical 16" rifles in just this configuration. It's the same barrel I used last year in competition, as did Tony Holmes. 1/2 - 3/4 minute right from the factory. I also have a Tactical 16 as one of my AR's I use at my PD job. I found one ammo that would just not run my gun but that was old SAMSON ammo the department found cheap several years ago. Everything else runs great, factory 55's, green tip, 50 gr. reloads, right up to current military 77 gr Sierra's.

Bushmaster offers a 16" barrel with a long sight radius but they have the short gas system UNDER the handguards. The sight block at the end doesn't have a gas port in it.

Edited October 5, 2009 by BPiatt

[jmurch]

+1 on what BPlatt says.

I have a 16" cut down from a 20". 1:7.7 twist, rifle gas, full length hand guards, 20" sight radius. It operates on any ammo so far from commercial PMC to my handloads (LC, Rem 7 1/2s, 24.5 varget, 77grn hpbt).

Yes the gas port is enlarged I think to .100. It runs very smooth, not anywhere near as sharp a recoil as a carbine 16". With the Miceluck (spelled wrong I'm sure) compensator it is really nice to shoot.

Jeff