I took my AR out to the range today for a little fun time and trying out all the new stuff I put on it. I have never had an issue with the AR jamming or anything at all. Had a good day today, tore up a target pretty good. However... I normally only take about 200 rounds with me to the range to shoot. I decided to bring an extra 100 today and put 300 rounds down range. It was at round 201 that there was an issue. I put the mag in and the round wouldn't chamber. So I removed the mag, kicked out the round and put the mag back in. It was fine. Until the next mag. I put it in, the round partly chambered and I pushed it the rest of the way in with the forward assist. From this point on, with every mag, I had to put the first round in with the forward assist. It got through 200 rounds without this issue, but that 201st round did it in. And didn't matter if I used the release or the charging handle to get it started, I still needed to use the forward assist. And this is the first time I've ever actually had to use that. As for the gun itself, it was very clean going in. It gets cleaned as soon as we get back from the range every single time, and once a month when not in use. The changes I made to the gun were purely cosmetic and nothing was changed about the actual functionality of the gun. Stag Model 2. PMC FMJ 55gr. ammo, all 300 rounds. I assume it just got an attitude from being dirty, but after only 200 rounds? Any ideas?