I am was surfing and found this forum and thought I would chime in. I shoot Sigs....Now before I get run out of town on a rail, I have been reloading for many years and went over the "glock" bulge issue first hand a few years back. I reload for myself and a friend (who is Glock only) and found the bulge to be an issue. I get all my brass from a police range and know for a fact that 99% of that is fired from Glocks. In the beginning I did not use the bulge buster or the redding Grx and it was O.K most of the time, however there were several occasions of failure to feed in both Sig and Glock, they were not chambering all the way. Since using the Redding Grx that has gone to no failure to feed.
When the entire case is pushed through the die it sizes all the way to the base (base is now .420 my books give .424 as max at the base). That gives me confidence in my brass with out a question. There is one caution with using the push through dies, measure your cases after decaping/size and the push through. In many cases the brass becomes longer on one side, the bulge side. It so happens that sometimes one side of the case is .848 and the other side is .853 or longer, .851 is too long! I will set my calipers to .849, and if the brass passes through I'm good to go, if not then trim or toss.