View Full Version : Need HELP on LMT MRP Piston!!!

02-21-2011, 10:26 PM
I have a LMT MRP Piston upper w/ a 16" barrel and after i did my first clean around 350 round, i have a similar problem with the BCG not locking back after the last round been fired. Anyone know why this is happening? I currently use the LMT H2 buffer. I cleaned the gun again after another 350 round and the bcg is only occasionally locking back.

Currently using pmags 10 round 30 body
tried pmags 10 round 20 body, no difference really, was working fine before my first clean, so im kinda confused

had three occasions where gun jamed, the bolt only pushed half of the bullet into the chamber, thats out of 700 rounds

shooting mostly pmc and fiochi 223 55 grain fmj, i know pmc make gun dirty easily but even if i just cleaned and lubed, its still not locking

All feed back greatly appreciated !!!

02-22-2011, 7:47 AM
You need to back track your cleaning/dis-assembly that was done.
My GP rifles have an adjustable gas block. Normal and suppressor modes. Set to normal.
LMT? Gas rings on op rod need checking?
Next look to your bolt stop/BB adjustment. Too tight or too loose can cause problems.
H2 buffer because H wouldn't work?
Ammo choice has never caused me any problems with my GP guns.
Lastly swap mags with range buddy and rule them out.
Good luck.

02-22-2011, 8:21 AM
And if you continue to have an issue call Gene Swanson at LMT -- he is the shop boss and when I had a short stroking GP last year it turned out to be a magazine problem.

Group B
02-22-2011, 9:55 AM
LMT MRP Piston uses H2 buffer normally, and gas block positions are closed and normal.

02-22-2011, 10:30 AM
I had the same exact same issue with my MRP DI, but the issue was gone after 300rds or so. I think the clearance between BCG and the upper receiver is the issue.

02-22-2011, 12:22 PM
cool, thanks alot for all the feedbacks!!! i will try out other mags/ammo and see if things change out