Size Matters
The first bit of useful trivia is that even though Small Rifle and Small Pistol primer pockets share the same depth specification, Large Rifle and Large Pistol primers do not. The standard pocket for a Large Pistol primer is somewhat shallower than its Large Rifle counterpart, specifically, 0.008 to 0.009 inch less.
A number of handloaders found this out when one of the “mega-magnum” handgun cartridges appeared a few years back. Original cases were formed for Large Pistol primers. Some reloaders decided to switch to Large Rifle primers to better handle the high pressures, and they found the rifle primers stood proud of the case head, an unpleasant situation in a high-recoil revolver cartridge.
Read more:
http://www.shootingtimes.com/2011/01/04/ammunition_st_mamotaip_200909/#ixzz2kO5vWABE