At the TVI shoot on Saturday, my M&P15FT wasn't behaving well. Fairly consistently, it would jam on the 3rd round of a magazine. MassMark and others helped me with it and it looks to be ammo related but here are the clues:
- Problem happened with QMMO .223 reloads. I tried 20 rounds of XM193 5.56 and those went through just fine. I have previously used about 600-700 rounds of the QMMO stuff with no problems until Saturday.
- I cleaned the gun (really just the upper and bcg) the night before the shoot and lubed it well with Mobil 1.
- I tried a variety of different magazines, all did the same thing.
- If the bolt was closed, magazines don't seat with a satisfying click. If the bolt is open, all is well.
- The jam was a ftf. The round would be jammed on the feed ramp with the bolt on top of the case, always right before the case necked down, leaving a crease in the case.
- I could feel and hear the difference in the first two rounds of one of these incidents. The first round would feel and sound good. The 2nd round would feel a bit week and the 3rd would jam. It seems the bolt wasn't cycling all the way back between rounds 2 and 3.
- We tried Mark's BCG in my gun and it gave the same behavior.
Mark was thinking the buffer spring was too strong and he's probably right but I wanted to see what the brain trust here though. By the end of the day, I was thinking of selling it and getting a Sig 556.
Any help is appreciated.
- Problem happened with QMMO .223 reloads. I tried 20 rounds of XM193 5.56 and those went through just fine. I have previously used about 600-700 rounds of the QMMO stuff with no problems until Saturday.
- I cleaned the gun (really just the upper and bcg) the night before the shoot and lubed it well with Mobil 1.
- I tried a variety of different magazines, all did the same thing.
- If the bolt was closed, magazines don't seat with a satisfying click. If the bolt is open, all is well.
- The jam was a ftf. The round would be jammed on the feed ramp with the bolt on top of the case, always right before the case necked down, leaving a crease in the case.
- I could feel and hear the difference in the first two rounds of one of these incidents. The first round would feel and sound good. The 2nd round would feel a bit week and the 3rd would jam. It seems the bolt wasn't cycling all the way back between rounds 2 and 3.
- We tried Mark's BCG in my gun and it gave the same behavior.
Mark was thinking the buffer spring was too strong and he's probably right but I wanted to see what the brain trust here though. By the end of the day, I was thinking of selling it and getting a Sig 556.
Any help is appreciated.
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