Another board has a post about one of these snapping the last couple of threads off in a bit of unusual circumstance.
The shooter's allen wrench was stuck in the head, so he turned it back in a couple of threads to hold while he pulled on the wrench.
The last couple of threads snapped off when he pulled back on the wrench.
Again, this was an unusual situation, but it is worth noting, in case the same thing happens with your allen wrench.
The liner is counterbored and the threads are very thin on the tip, so be sure and turn it back in more than a couple of turns if the wrench is stuck.
