I'd like to get a length that is exactly 16" with a regular A1 flash hider pinned.

Problem is cutting down a 0.625" barrel will make the contact area with the flash hider too small, since I lose the up-taper near the muzzle. Looks like I'd need something of this sort:



Photo courtesy Randall (ar15barrels). I don't think I'll be sending it to him. Does anyone else do this work/manufacture this bushing?

Without trying to turn this into a GD thread, I've nothing but good dealings with Randall because he performs the work while I wait.  The subject of installing a collar or bushing on a cut-down 16" pencil barrel did come up in one of our many conversation in his work shop.  Randall no longer install the collar or bushing as he does not think it's necessary, especially if you're going to use an A1 FH.  Randall believes that if you use an A2 FH, you're more likely to need the bushing due to potential over torquing in an attempt to time the A2 comp.  I just like the look of the bushing since the original Colt barrels had them.  Just my 2 cents.

I was going to attempt the same thing - There is another option.  But requires permanantly attaching muzzle device.

Get a 14.5 LW barrel.  J&T has them.  They take forever to ship but they have 14.5 and 11.5 LW barrels.  You can extend an A1 flash hider out to the 16" mark by using another washer and welding or pinning.  Unfortunately its a fairly permanent thing,

Adco does this all the time, among others. You're overthinking this.

This, every carbine barrel I have ever owned was cut down and the shoulder was never a problem.

Yeah, JT did the chop on my faux Israeli "Nickel Grass" gun. He just said not to go crazy torquing it down, and there was no need to since the flash hider didn't need to be clocked.

I also had a 16" pencil barrel cut-down to 14.7" and had an A1 FH permanently attached. No issues.