Testing Primer "Impulse"
A 1997 test with the 45 Colt, using a fired case that had sufficient elasticity to retain a bit of crimp roll at the mouth and Hornady swaged lead bullets demonstrated vast differences in propulsive force for various large-diameter primers. Included table shows results of that study, where primed case (modified to work with both Pistol and Rifle primers) held a finger-inserted Hornady 250-grain Swaged lead (Cowboy) bullet at identical normal cartridge length in each test. We used the same chamber of a standard Ruger 45 Colt revolver as the test vehicle.

Apparent Primer Energy, as a Function of Bullet Displacement (six shots with each primer)