I'm reloading .204 Ruger for a DPMS upper receiver using RCBS AR dies. My issue is that once the brass has been fired it doesn't seem to fit in the resizing die. I can force it in of course, but then it gets stuck. I've used RCBS case lube, Frankford Arsenal case lube and 3 in 1 oil as a substitute case lube. They all produce the same results. I'm using the #10 shell holder and it rips right through the rim of the case. It seems as if my DPMS upper has a larger than normal chamber and the die won't accept it. This issue is the same on both Hornady and R-P brass. I plan on trying Imperial case lube once I get a hold of some but it's getting pretty frustrated. Any advice would be appreciated.