I just picked up a 20" Bushmaster barrel and I can't decide what to do with it. It is a 20" HBAR with a target crown. I am thinking about getting the barrel threaded....Anyone know how much this might cost? Also, I can't decide whether to build a standard A2 using the HBAR, a 20" Varminter, or something else? Any suggestions would be much appreciated.

I believe that AR15barrels.com does it pretty cheap. Well respected also. No sure how much but I think it is less than $50 plus shipping both ways.

If it is an Hbar you could just build it into a model with standard handguard model or you could do it with a FF tube. My personal choice would be FF, either round tube type or railed.

Qutoed from "shop services" @AR15Barrels

Barrel Threading $30
This is the most commonly requested service. The barrel gets mounted in the lathe with a live center in the muzzle. The muzzle gets turned down to the required size and then threads are cut with a single point tool. This ensures that the threads will be perfectly concentric and parallel to the bore. After the threads are done and deburred, a new crown is cut to eliminate the damage caused by the live center. Other shops would consider this a 'precision' threading job. I can turn any of the common thread sizes such as 1/2-28, 1/2-36, 9/16-24 or 5/8-24 with verification from my gauges and tooling. The threaded area will be finished with touchup bluing.

AR15Barrels.com