Ernest Durham developed the 45 Glock Automatic Pistol (GAP) in 2002 to duplicate 45 ACP performance using a shortened version of the 45 Auto case in a shorter round that fits a more compact grip frame. To achieve this goal, the 45 GAP uses the best modern propellants and is loaded to somewhat higher pressure than the 45 ACP is. While nothing is wrong with the 45 Gap it has not been the booming success Glock envisioned when it asked Durham to develop it. Likely, the main reason for this lack of sales is the same problem that plagued the 1911 Colt: few shooters have the patience and determination to master any handgun that generates significant recoil, so, regardless of the fight-stopping advantages such chamberings offer, they prefer guns that generate less recoil. The logic of choosing a smaller-caliber gun, compared to the 45 GAP, for folks whose lives might well depend upon rapidly stopping a bad guy in a life-and-death situation evades me but what does logic have to do with it? And, in fairness, a gun the owner will practice with and thereby learn how to use effectively is far more valuable than a gun the owner will not practice with and which he or she can therefore never use effectively, at least not on purpose! As we tried to drill into our students in our concealed carry classes, the absolute best possible gun in a self-defense situation where your life is on the line is always the gun you have with you — the 22 pistol you have in your pocket always beats the 12-gauge resting in your closet at home! As with any pistol round headspacing on the case mouth, best practice is to apply a taper-crimp after seating the bullet. This helps to lock the bullet in place against chambering forces that might otherwise drive it into the case. I cannot too-strongly recommend getting a second seating-and-crimping die so you can have one adjusted to seat the bullet and the second adjusted to only taper-crimp the case mouth. Generally, attempting to do both operations in one step is a recipe for damaged and destroyed cases.