Gunsmithing AR 15 barrel set back??

[CanSniper]

I have a AR barrel that I could utilize if it was set back. In other words, cut the tenon off and rethread.

This would move the gas port back toward the action. Meaning the gas tube would need to be shortened. The same amount that is cut from the tenon.

Is this a acceptable practice??

 

[kl3309]

How many rounds down the barrel? How much erosion at the gas port? Will you have to drill out the gas port to get proper cycling?
If you're doing this yourself as a project, go ahead and see if you can make it work. If you're paying for it to be done, I'd say just get a new barrel.

 

[whatsupdoc]

Buy a new barrel, unless you are doing it yourself to play and learn.
Setting back a AR barrel is not something that is commonly done for a reason.

 

[Ledzep]

The amount you set it back has to match exactly in 1/16" increments (thread pitch) in order to get the barrel extension to time up with the gas port at proper torque. Depending on the contour, length, and gas system currently, I'd aim to shorten it enough to hit the next common gas port location personally.

I agree with the above, if this is for a project, go ahead. If it's something you're going to have someone else do ($$$) then pass. If I were a GS I'd charge more to do what you're describing than I would to start from scratch because it's honestly more work.

 

[CanSniper]

Sooo kind of a long story on the barrel.
It has less than 50rnds on it. I bought it from what I thought was a reputable smith. The chamber was cut so rough it looked like a 1st grader cut it with a sharp rock. The brass that came out of it looked horrible. Surprisingly it was very accurate even with a shitty chamber.

I did call the smith and he did say send it back. But he took forever the first time, and I am of the mind set that if you can't do it right the first time chance's are pretty good that it is not going to be timely or right the second time.

I did buy a lathe, and I have been practicing and trying to learn on my own. Been practicing on some old scrap barrels. I thread and chamber one, then cut it off and start all over. Untill I run out of useable barrel. Been doing that for a couple months. Felt pretty confident...chucked this baby up, set the shoulder back .062" or one turn on the the extension to put it back in time with the gas port. Was going to set the chamber back a equal amount with the proper reamer. My dumb ass cut it to deep. I don't know how much further back I can go with the gas port as a result of setting everything back (shoulder/ chamber).
I am just trying to learn and it has been something I have wanted to do for a long time. Maybe jumped the gun on this particular project, but you never grow if you don't try.

 

[Hateca]

There are so many good off the self barrels for the AR’s unless this is some custom chamber I would never pay or chamber one myself. It’s just not cost effective.

Could it be done? Sure but it would depend on how far, what the barrel profile is or was, and a lot of other questions that can‘t be answered without seeing the barrel.

 

[Ledzep]

In that case, yeah just cut it back another thread then lop 3/16" off the gas tube and call it good.

ETA: To be sure (whether or not you need to cut the gas tube), you can do the barrel work, install it in the upper, install a gas block w/tube, then close the bare bolt carrier in the upper. It should hit the breech face of the barrel extension before the tube bottoms out in the key.

 

[81STFACP]

I have a AR barrel that I could utilize if it was set back. In other words, cut the tenon off and rethread.

This would move the gas port back toward the action. Meaning the gas tube would need to be shortened. The same amount that is cut from the tenon.

Is this a acceptable practice??

I have done a few, salvaged 18 inches or even 16 inches from service rifle 20 inch take off barrels.

As far as the old gas ports, I just drill and tap them for 8-32 set screw. I do not drill all the way through, run a plug tap just enough to sink the set screw below the surface. Drill/ream the new gas port. Sometimes, depends on the set back, I don't even plug the old port. I just let the gas block cover it. A blind hole does not hurt anything.