Common bolt over, and would dare to guess from lack of cleaning and lubing.

Start by cleaning the rifle, including scrubbing the chamber with a Chamber brush and CLP.  after the rifle has been correctly cleaned, lube the upper receiver bearing areas by apply CLP to both the inside and outside or the B/C, put the CLP wet B/C in the rifle, the cycle it a few times to transfer the CLP on the B/C to the upper bearing areas (leave the action wet with CLP to run the rifle this way).

Next, pull the mags apart, and CLP clean then as well.  On the mags, do not leave them dripping in CLP like you did the upper, but just slightly moist with CLP instead.


As for the steel coated ammo, run the rifle on the wetter side of CLP lubed as pointed above.   Also, during the break in peroid of the first 500 rounds, pull the B/C every 200 rounds (if you are going to fire that long of strings), and relube the B/C as pointed out above (don't worry about wiping the fouling off the B/C, just relube it as is, and put it back on the rig).  CLP has a cleaning agent in it, and will disolve the fouling as the rifle is being shot).