Quoted:
3 thousand? Thats way to early for worn parts.
Actually, that's about when mine gave out on my LMT. Same failure. Retaining pin popped out (you can see the little hole in the picture) and completely locked up the FCG
I don't know if I can blame it on the LMT though. The lower is from a M&P15 and the commercial extension tube came with a Magpul ACS stock I found cheap at a gun show. Between the crappy ATI extention tube and M&P15 lower, there could have been enough tolerance stacking to cause excessive wear. To be fair, most other LMT pistons I've seen don't have nearly the carrier tilt problem mine did.
I'm now running a Magpul UBR stock and Slash's H2 buffer. There is now some cosmetic scuffing (from the enlarged carrier and skis) after about a thousand rounds, but nothing anywhere near as bad as before.