Cool thanks! This one's cheaper..
I just got back from Mexico and I looked at my FSP again and it looks like my gunsmith tapped them from the right direction. Can't really remember his explanation that well but it seems like he knows what he's doing. He said he was an armorer for the Canadian Forces and he is from a store that specializes in black rifles, with him being the "AR guy". Anyway, after checking out the suggestions, it seems that the Troy Charlie/Delta rails are the way to go as they drop in and require no gunsmithing at all and are cheaper than the Centurion which requires a bit of modification. Thanks for all the replies!
If I'm not too late to the party - did he let some penetrant like Kroil work it's way into the piece before he started bashing? Just curious.
The Centurion arms c4 is worth the extra $$ over the Troy... I have both.
The CA is the best quad rail that uses the standard barrel nut hands down.
Troy has had issues with rails being crooked or curved from the manufacturing process. I have the centurion and can tell a difference in the quality. I'm not sure how there would be any modification needed compared to the troy rail on installation that you were referring to.
I was thinking of the B rail. From looking at the pics of the mounting surface of the C/D rail, I wouldn't trust it at all. It barely hangs on to the barrel nut and relies on a ring to hold in place on the remaining barrel shoulder, which depending on your barrel profile could be very minimum. Also when you tighten the screws from the rail wouldn't it pull the ring away from the barrel making the only thing to really contact the barrel is four points of contacts from the screws protruding through the ring or just pulling the ring away if they don't protrude at all? Rather than clamping tighter onto the barrel/barrel nut like the Centurion rail? Surely if your GS can't remove the pins he could at least remove the barrel and take the delta ring and retainer off and only modification would be cutting the handguard end cap. Sometimes the shortest easiest route isn't the best.