"When using one I had 3 failures to lock the bolt back on an empty mag. I will test it further to see if it will go haywire with a FatBoy and LMT bolt/carrier next week."
My bet is YES it will go haywire.
If you are getting the Fatboy and LMT blockII carrier to cycle you either are one lucky bastard or have an erroded gas port. I took out my LMT 10.5 and put the Block II B/BC in it and fired about 65 rds and it was experiencing short stroking and FTF's about every 3rd round, toward the end it smoothed up a little and I managed to get off one 13rd burst. Yeah it was SLLLOOOOWWWW sounded like a greasegun POP-POP-POP-POP-POP-POP-POP-POP-POP-POP-POP-POP-POP my guess would be it was at about 450RPM.
Maybe with time this combo will become reliable but I know I won't need to use an H-buffer untill I get my KAC M4 QD.
[b]The fatboy and the LMT BC are both doing the same thing, robbing the gas of it's power to cycle the weapon (retarding the cyclic rate)- if you can get it to work it is cadillac smooth slow ass FA fire though. I had those 13rds inside a coffeecan at 25yds[/b]
My deer rifle (16in DISSY) has a PRI Fat boy tube and AAC buffer, I'll let you know how that works out by next week. (I have to find time to get to the range, my rifle isn't sighted and deer season is 9 days away!)