Well, so as to cover the buttocks... Users manual says not to use reloads in Glocks (as do all pistol manuals).
Now, on to the problem. The first thing I'd do is take an empty piece of brass and run it thru your sizer. Disassemble the pistol safely and insert the resized brass into the chamber. Note any fitting errors as compared to a factory round. Also, if you have a set of calipers, check dimensions of factory round vs. resized round at mouth and base.
My first guess is that you need to reset your sizer die so that it sizes the whole round. This would be the problem if the round is failing to seat or go into full battery.
My second guess would be that you need to check the OAL (over all length) of the rounds. Make sure they are within specifications, if not adjust your seating depth to correct specifications. Also check the brass length. If you've shot those pieces of brass alot, they may need to be trimmed back a little.
A little more information on what kind of jams you are getting will help to diagnose the problem as well.
Hope that helps out. Let us know