Greetings fellow reloaders. I have a simple question, that I'm sure will draw debate. LOL! Today I was reloading some ammo for my MP15. I started loading Winchester .223 cases. At some point, I began loading NATO marked Winchester 5.56 cases with the same load. I am using 25.9 grains of Ramshot Tac behind a 53 grain Sierra HP Matchking bullet. Which should be pushing about 3100 fps with the .223 cases. My Sierra book lists something like 26.7 grains as a max load. I'm guessiing that these will be ok to fire, but I thought I should double check with some of the experts here first. Will the NATO cases cause any signifigant changes that could be a problem?