So I took a new toy out this afternoon, an AR15 pistol in 9mm with a barrel length of 8.3 inches. I put together the lower last weekend, the upper came assembled. Today since the weather was nice and since we have winter storm weather moving in, I decided to take a half day off to get familiar with the gun. Before I took it to the range, however, I tried chambering some ammo just to test things out, and I found that ammo with a shorter OAL seemed to have issues feeding. The 9mm ammo I normally make is 125gr LRN over 4.9gr of Unique, loaded to 1.100 OAL, which is pretty short. For this test, I loaded up 30 that were loaded to 1.155 OAL instead. I started off shooting WWB ammo. I noticed that the empty cases were very dirty. I assume this is because WWB is loaded pretty light - does that makes sense? The primers looked normal to me. I finished up shooting those 30 reloads. The brass looked quite a bit cleaner. The thing that really jumped out at me was the primers. When I load these to 1.100 (shorter, higher pressure in theory) and shoot them in my compact gun with a 3.4 inch barrel, the primers look normal. Some of these look very flattened, more so than I've seen before, personally. FYI, primers are S&B. So, what do you say? Does anything here look alarming? Thanks!