My load is: Once fired LC/WC 5.56 brass (left uncut, once fired) LC 55gr FMJ projectiles #41 primers H335 power COAL @ 2.2150" So I've been working up a load for this bullet, all was well with ~100 rounds downrange loaded with 22.8-23.6grs. of H335 when I went to try out my max/target load for this project, which was 25grs H335. Some sources/manuals show a max load as high as 26.5grs. All specs on these rounds are the exact same, except that I used exclusively Winchester brass for the 25grs. At the range, I warmed up the rifle with 3 of the 25gr rounds having fired the lesser 23.6s before. All three chambered fired, cycled and ejected perfectly. I then fired ~50ish rounds of the 23.6gr rounds, which also all worked perfectly and in a consistent manner. When I went back and fired 8 more of the 25grs, none of them ejected or allowed the next round to feed. The BCG would have to be locked to the rear and the magazine removed (but never ripped, as there was never a half chambered live round). Most often the live round would be jammed against the feed ramps, and the spent casing, ruined, jammed by the bolt above the barrel in the chamber. ...should have taken pictures :/ The rifle has a M4 feed style 16" barrel with a 1:9 twist and carbine length DI operation, fed from the same problem free Magpul mags. It has a commercial spec buffer tube and spring that I feel are the only low quality area of the rifle, save for the 'blue' rifle extractor spring where it should have a carbine one. I do a lot of handgun reloading, but this is only my forth project for my rifle. Thanks much for any advice. D.