Will a barrel with a fsp that has been shaved fit under the MK 18 rail without protruding? Seems like it will be a close fit.
Yes, a carbine length gas system with shaved FSB fits nicely and is fully covered by the Mk18 rail. I’ve done three like this and have been very pleased with the results.
I hacksaw the A frame off, then use a Dremel cutting wheel to profile the gasblock, with final finishing touches with a hand file, degrease, paint with Norrell flat black moly, let dry overnight and install the next day. I don’t oven cure the moly as I figure a few good fullauto mag dumps will take care of that…