Can usually be completed correctly, same day as dropped off.
I have blueprints from all major  suppressor manufacturers

Barrel threading for suppressor/silencer, or muzzle-brake.
Barrel can be cut to any length before threading (All NFA applies).
14.5″ M4 barrels can also be (ATF-approved) pin/welded w/ muzzle-brakes to meet 16.1″ legal length.

Threading is done Concentric to the bore, for correct suppressor alignment.  Much care/time is taken during accurate set-up.
AR Warner tooling (The Highest quality) is used for cutting threads.
VERMONT calibrated go/no-go gauges are also used, to make sure threads are within the Class-2A (+/- 0.003″) tolerance.

Remchoking is also available.