I'll walk you through a couple steps that should get you going with far less frustration and collapsed cases.
First thing, resizing. This only requires that you insert the shell holder in the ram, extend the ram fully, then thread the resizing die in until it just makes contact with the shell holder. Too much hard contact can fracture a carbide sizing ring.
Pick up the expading die / belling die, back the top threaded stem out all the way. Now extend the ram fully, then thread the die in until it makes contact with the shell holder, then back it out 1 - 1-1/2 turns, lock it down. Now with the shell holder installed, and a resized empty case inserted in the shell holder, run the ram to full extension, then start threading the expander stem in until you feel it make contact with the mouth. Back the ram down, adjust the expander stem down a little bit at a time until it's belled just enough that a bullet sets up on / in the mouth. It should just barely enter the case mouth, just enough to avoid shaving or catching on the case mouth. The trick here is to bell as little as necessary to accomplish seating without crooked start, shaving, or hanging up on the case mouth.
The area I strongly suspect is responsible for your problem, is improper seating die adjustment. So, insert the shell holder into the ram, insert a completely Resized piece of brass into the shell holder, then run ram to full extension, then thread the seating die in until you feel it make positive contact with the case mouth. Back the ram down, then thread seating stem out / up as far as it will go. Put a bullet on top of the brass, guiding it with your fingers into the die if necessary, then while the press is at full extension, thread the seating stem down until you feel it make contact with the bullet. Thread the seating stem down in small increments until you' seated the bullet to the desired oal, thus assuring it passes the plunk test.
Now rather than teach you how to seat and crimp in one step, I'm going to explain to you how to crimp after seating, it's easiest for a beginner to learn and get right, thus will save you some time, frustration, and components by doing so. So once you've seated all the bullets, back the seating stem out enough to assure it doesn't make contact with the bullets, 1-1/2 turns should do just fine. Now thread the entire seating die down 1/4 turn, run a completed cartridge up into the die, then check the case mouth to see if the bell has been removed,, if it has, you are finished. If not, then continue threading the die down in small increments, no more than 1/8 turn at a time, as over crimping is what caused your problem in the first place, and it will cause other serious problems also. So the rule here, is only crimp enough to remove any visible bell that remains after seating the bullets, no more, no less. More crimp on rimless cartridges actually reduces neck tension, which leads to an increased risk of bullet set back, not a good thing and it can lead to serious pressure spikes.
GS
