AR-15 barrel shorten/rechamber question

[pdhntr]

I have a Krieger 20 cal barrel that I want to cut down to make it lighter for another coyote rifle. I built it as a bench AR-15, and it just doesn't get used anymore so trying to make it more practical.

My question is, should I take off more barrel towards the chamber, giving more barrel out front and use a carbine length gas tube? (green arrows) OR, use a mid length gas tube, putting the gas port farther away, and taking more off in front of the gas block? (black arrows)

Maybe it doesn't matter, but I don't know if the gas port should be closer or farther away. The gas port is very large so I will have to use an adjustable block either way.

Thanks.

Jim

 

[jelenko]

How about just having the barrel recontoured?
My understanding is rifle length gas systems have fewer 'tuning' issues

 

[Walt Krafft]

Cutting off the chamber end and getting it headspaced and timed with an existing gas port can be a real pita. I would shorten the muzzle and recontour under the handguards as suggested to lighten it up.

 

[mac86951]

What do you have it chambered in? Maybe more cost effective to call White Oak Armament and get a new barrel.

-Mac

 

[Mark M.]

If you want to have the chamber end cut, not a big deal for a competent smith that is familiar with the AR,
Your basically just changing from a rifle to a carbine or mid gas length, consult your smith for options that make sense for your intended use.

 

[204 AR]

What's your overall length going to be either way? From your pic, definitely stay mid-length at least. I've thought about shortening the chamber end on a burned out 204 barrel but I figured on plugging the gas port hole and starting over. At the end of the day, by the time you pay someone to do it, it's not worth it.

 

[troupe]

Cut at the muzzle end, rifle length gas can go all the way down to 17" and maybe 16" depending on the gas port size. I have 3 rifles with rifle gas on 16" barrels, they shoot very soft and accurate. Also, you can take some meat out of the 1" behind the gas block.

 

[pdhntr]

How about just having the barrel recontoured?
My understanding is rifle length gas systems have fewer 'tuning' issues

Cutting off the chamber end and getting it headspaced and timed with an existing gas port can be a real pita. I would shorten the muzzle and recontour under the handguards as suggested to lighten it up.

I want to run a suppressor on it for coyote hunting, and with the suppressor, thermal, back up battery, I am trying to save as much weight as possible, and keep it as short as possible.

So far I haven't had any tuning issues with the two others I have, but I am using adjustable gas blocks also. Jelenko you are probably correct, but I think I might have a go at it.

Walt, I have headspaced and timed fluted barrels so unless I am missing something I think I can do it.

Jim

 

[pdhntr]

What do you have it chambered in? Maybe more cost effective to call White Oak Armament and get a new barrel.

-Mac

20 Practical. And this barrel is not practical for me any longer so I would like to change it and put it back in use.

If you want to have the chamber end cut, not a big deal for a competent smith that is familiar with the AR,
Your basically just changing from a rifle to a carbine or mid gas length, consult your smith for options that make sense for your intended use.

I am the "smith" in this case. I have my own lathe, reamer etc. That is why I am asking questions here as I don't know if I have thought of everything.

Jim

 

[pdhntr]

What's your overall length going to be either way? From your pic, definitely stay mid-length at least. I've thought about shortening the chamber end on a burned out 204 barrel but I figured on plugging the gas port hole and starting over. At the end of the day, by the time you pay someone to do it, it's not worth it.

I would like to go 16". I will be doing the work and not paying myself for it.

I was thinking mid-length also.

Jim

 

[pdhntr]

Cut at the muzzle end, rifle length gas can go all the way down to 17" and maybe 16" depending on the gas port size. I have 3 rifles with rifle gas on 16" barrels, they shoot very soft and accurate. Also, you can take some meat out of the 1" behind the gas block.

And I hadn't thought of that, but I kind of wanted to run a shorter hand guard.

Just a rough measurement with the calipers, of the gas port, and it looks like it is close to .090. I have an adjustable gas block for it.

Jim

 

[troupe]

16" barrel works great with a 15" tube, as long as your Gas Block fits inside of the tube. It would be a great setup for carrying. Very handy.

 

[troupe]

18" of coarse will give a little more velocity and still be handy. When I used to shoot 3 gun, I ran 18" barrels. My AR-10 is a 18"

 

[Minshooter]

Those telling you to use go to 16" and keep the rifle gas tube are absolutely correct.
These make the smoothest shooting 16" ever, in particular with a rifle buffer system.
Used with a suppressor, you might possibly find the adjustable gas block set to wide open.
The exception might be if using a .45 caliber rifle can (Hybrid, etc). That almost 1/2" hole
doesn't hold back much gas (but in your case, that .090" hole is already pretty big).

 

[pdhntr]

18" of coarse will give a little more velocity and still be handy. When I used to shoot 3 gun, I ran 18" barrels. My AR-10 is a 18"

Those telling you to use go to 16" and keep the rifle gas tube are absolutely correct.
These make the smoothest shooting 16" ever, in particular with a rifle buffer system.
Used with a suppressor, you might possibly find the adjustable gas block set to wide open.
The exception might be if using a .45 caliber rifle can (Hybrid, etc). That almost 1/2" hole
doesn't hold back much gas (but in your case, that .090" hole is already pretty big).

I just didn't think a rifle length gas tube with a 16" barrel would work, but I have no background in this endeavor. That is why I am asking for advice.

I don't know if this will help, but the setup I am looking for is very specific. The thermal I am using gives me confidence of identification and shot placement to about 300 yards. I have a 223 AR that I was going to use it on, but if I can get this thing figured out for 20 Practical shooting the 35 Berger, it would make the occasional 300 yard shot somewhat easier to make.

18" barrel length might be an idea also.

Minshooter, I think the gas port is .090, and the suppressor is a 30 cal.

I know it blows a hell of a lot of gas back into the chamber on the 223 AR.

Jim

 

[edwardware]

I just didn't think a rifle length gas tube with a 16" barrel would work, but I have no background in this endeavor.

You would be making an olde timey Dissipator, a rifle length bbl with rifle gas, cut off with just enough room to screw the flash hider on ahead of the rifle length handguards.

Starting with a large port, and a willingness to fool with buffer and spring as necessary, you should be able to tune up a very soft shooting gas gun. Since you can do the work yourself, you should absolutely try it.

I know it blows a hell of a lot of gas back into the chamber on the 223 AR.

If your gas system blows gas into the chamber, you may have a more fundamental problem. . .

 

[pdhntr]

You would be making an olde timey Dissipator, a rifle length bbl with rifle gas, cut off with just enough room to screw the flash hider on ahead of the rifle length handguards.

Starting with a large port, and a willingness to fool with buffer and spring as necessary, you should be able to tune up a very soft shooting gas gun. Since you can do the work yourself, you should absolutely try it.


If your gas system blows gas into the chamber, you may have a more fundamental problem. . .

I don't think there is a problem, just didn't state that right. The suppressor causes a lot of dirty brass, a problem that seems to be very common.

I won't find most of (the brass) that goes through this, so it really doesn't matter.

Jim

 

[troupe]

I have that setup you are speaking of, only in a 223. My can is on a 223 and it is a 308 can, it won't be bad (dirty) since the can has a larger bore. Wont be as quiet as a dedicated can, but it will work. Also, you should not loose much brass with the thermal, the brass will glow in the dark with the thermal.

 

[pdhntr]

I have that setup you are speaking of, only in a 223. My can is on a 223 and it is a 308 can, it won't be bad (dirty) since the can has a larger bore. Wont be as quiet as a dedicated can, but it will work. Also, you should not loose much brass with the thermal, the brass will glow in the dark with the thermal.

Interesting. I have had the can on a 223 16" AR for several years. Brass comes out filthy, but the gun keeps running fine, so I don't care. At this point I have about 5 grand into that gun/thermal, and all the gear to hunt coyotes at night. I don't know how long the brass will glow in the snow, but I ain't going to be lookin' for it.

Jim

 

[troupe]

Makes sense. My scope is a Pulsar. I have not had a chance to kill coyotes back this way with mine. It is a ball to have.