As far as I know the preproduction models had a brake that was pinned and the pin was welded to the brake after pinning. Apparently the pin could be drilled out and the brake removed. Someone may correct me on that. The hole for the pin is on my brake but there is nothing in it, I can see the threads on the barrel through the hole.
The barrel and bolt look similar to an AR but that would be a good question for a dealer.