I was wondering how they mathed this one out. 13.5" barrel, pinned and welded brake, meets the 16" requirement. Well, I certainly know now - the brake is HUGE!
OAL on the brake is 3.438", and max internal threaded depth is 0.850". Even if the 13.5" barrel has a threaded end that's 0.850" long, the brake will still add 2.588" to the barrel length, when permanently attached. That's a 16.088" overall length.
The brake came with 6 drill-able inserts, and timing shims to set it up. Very nice. Barrel gets here Tuesday.
This will escalate quickly.