Hello all: I recently purchased a 9 mm Ruger Light Compact Revolver (LCR ) and have since been reading about a phenomenon called "crimp jump" that occurs when a round such as 9 mm, which has essentially no crimp and is typically fired from an auto pistol, is fired from a revolver. The bullet jumps the crimp as recoil causes the case to back away from the bullet. In the extreme, the bullet can be moved forward enough to bind the revolver's cylinder from rotating. So, equipped with some reloaded ammo, and some Hornady Critical Defense and Critical duty, and my micrometer, I set out to see if this phenomenon occurs with my carry and practice ammo. All rounds were measured for OAL before firing, and then I re-measured the OAL of the last round after firing the first four. The results surprised me. In every case the fifth chambered round was .020 to .025 longer than it started out. Eg the Critical Duty ammo started out with an OAL of 1.120 and after firing four rounds, the fifth had an OAL OF 1.145". The amount of increase was not perceivable to the naked eye with the factory ammo, but I certainly noticed it with one my reloads, which jumped double the amount as factory. Conclusion: whether perceivable or not, ammo meant for autos does jump crimp in a revolver. How much depends on the ammo. Solution: I now run a good roll crimp on any ammo designated to be used in my LCR 9mm, and Mark the box as such. I have not had a single problem with crimp jump that caused any stoppage so far. The roll crimp is just a precautionary measure. Now it's back to the range with micrometer in hand to see if the roll crimp fixes this issue. Meantime I must say I love my LCR 9mm and carry it daily.