Try this experiment if you really believe that the crimp is what holds the bullet in the case. Look around your house and find something like a baseball bat, a rolling pin, a broomstick - whatever you got. Now, using only the thumb and first finger of one hand, hold it as tightly as you can while someone tries to pull it straight out of your hand. Can you hold onto it? Probably not. Now try it again but this time using both hands wrapped around the object as tightly as possible. Get some meat on it. I'll bet it is MUCH harder for your partner to pull it out of your grip this way if he takes it away from you at all. One hand with your fingers is the crimp. Both hands around it - is case neck tension. The crimp adds a little bit of resistance but it's not going to hold it by itself. It just doesn't have enough grip on the bullet. You're asking for a thin sliver of soft metal to do more work than it is capable of. When I seat a bullet (with no crimp applied yet) I can press the nose of that cartridge into the edge of the bench as hard as I possibly can - and it will not move. If the cartridge can't hold the bullet with only neck tension then the bullet is undersize or the case was over expanded (or both). No crimp will fix it.