Took my new LMT M4 out today for the first time. The only problem I had was with Hornady TAP FPD 55gr. I only shot 10 rounds of it but had two FTFs due to short cycling. I could tell that the 55gr ammo was not as powerful as the 75gr FPD. Anyone else had a problem with it? My LMT has an H-Buffer.
First:
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Second:
More that likely you are ‘over-buffered’, try a CAR weight buffer and lube your rifle very well and use known good mags. LMT uses smaller gas ports and makes their rifles to reliably work with 5.56mm NATO pressure ammo with a CAR weight buffer. If you add a heavier buffer and use weaker .223 REM (SAAMI spec) ammo along with a heavier buffer you can encounter problems. It would be the equivalent of putting 87 octane in a truck that specifically requires 93 octane and then loading it down with 5000lbs additional pounds…it’s probably not going to run well.
More than likely you won’t need a heavier buffer until you have 5K rounds or more through the LMT.