Marvel conversion with Federal HV Match Gold Medal

First topic message reminder :

I recently switched from Eley Sport to Federal Premium HV Match Gold Medal and on a couple occasions I've experienced two shots for one trigger pull.  I tracked down the cases from those shots and this is how they look:




Obviously the rounds were fired before the case was fully into battery, hence the bulge at the bottom, and the strikes on the rim seem to be a bit lighter than normal.  I'm using the same lower for my service pistol, and the half-cock notch is good so the hammer isn't following.  I still have the stock recoil and firing pin springs installed that came with the Marvel conversion.  

I'm thinking that the HV ammo with the stock recoil and firing pin springs are causing the firing pin to rebound and hit the rim as the round is on the way to be chambered, causing the firing before it is fully into battery.  Perhaps I need a bit stronger recoil and/or firing pin springs with the HV ammo?

Has anyone seen anything like this when firing HV ammo out of the Marvel conversions?

DavidR wrote:you might want to check the federal rounds. I had several cases that had larger rounds in them than my aw93 would chamber. I had to switch to eley or aguila to get rid of the problem, mine didn't bulge the case cause the rounds would no chamber far enough to fire.

exactly what happened in my case. I had several thousand rounds thru my Marvel, but when using Fed711 it would double. The only variable that changed was the ammo. The IZH had far fewer rounds but the doubling occurred immediately after changing to Fed711, first match actually, six second series of Olympic RF. one of those 22 case gauges would probably detect a trend in rim thickness. I just used different ammo and never had the problem again.