Tons of bolt-over-base malfunctions...help
What causes bolt-over-base malfunctions?
Weapon was a Noveske complete SBR with H2 buffer, mil-spec spring, 10.5" barrel, Surefire 556-212, and was lubed generously with FireClean (after a thorough cleaning and de-greasing per Larry Vicker's instructions with MPro7). I even had a few of these failures when using the bolt-release on a fresh mag. I could only shoot 5-10 rounds in a row between failures. The weapon never was very reliable, and is just my plinker, but this outing was particularly pitiful to the point where I couldn't even make it through a 2-2-2 or 1-5 drill. The only thing I changed was going from an H to an H2 buffer, and lubing with FireClean instead of Rand or Froglube. Multiple PMAG's were used and PMC XTAC M193 was the ammunition. Shooting was done both from the bench monopoding off the mag, and kneeling/standing with mag not touching anything.
Sometimes, the round would be in the chamber, but the bolt would not be closed fully. Just resting on the case head. Dead-trigger. Other times, it was a classic bolt-over-base with the bolt slamming into the side of the half-fed cartridge.
Could this be part of the out of spec lower on the rifle not holding the mag at the correct height in relation to the upper? I've always had SOME issues with these Gen II guns, but this was just absurd, and worse by far than in the past.