Anyone notice that cases fired in .45 Glocks are difficult to resize ?
Has your brass been cleaned? Try a little spray lube even if you are resizing with Carbide dies!
jcelect
Lots of variables here. Glock chambers are usually on the large size, so Glock brass plus a tight resizing die could result in extra pressure required to resize the brass. The brand of brass could also play a role. Not all brass is created equal, some are thicker than others, some alloys are harder than others. Then there are the steel cases, which some are plated with brass, making them look like regular brass cases.