Primer strike problem

M

mcg6637

Inactive
I have a Greatwestern II .357 SAA.
I've had several instances where, after firing, the cylinder wouldn't turn or it seemed very tight. I've discovered it's because, when the hammer hits the primer, it often "mushrooms" metal high enough to rub on the back of the frame where the hammer protrudes from the frame. The hammer is a typical pinned in rounded nose Colt style. It sticks out appox 1/16". I do not know if this happens on the same cylinder every time. However I see nothing different about the way the shells sit in the cylinders and all the primer strikes look the same just to varying degrees.
Is this just a matter of flattening out and reducing the hammer nose ever so slightly? Or perhaps changing the mainspring to a "less aggressive" one to reduce the strike force? Opinions or previous experience would be appreciated.
 
Reply

American Eagle Factory. I've looked at the remaining cartridges and the primers are not set too high. I've used this ammo many times before. I haven't had a chance to see if I have the same problem with other brands but I've never seen this "mushrooming" effect before, so I assume it has something to do with the gun.
 
Firing pin hole too large, allowing primer cup metal to flow around the firing pin point.
Mainspring too weak letting primer pressure to extrude cup metal and push the firing pin back.

Worth a call to EMF
1-800-430-1310
 
I'll almost bet on a weak mainspring, cut down in an attempt to lighten the cocking force and/or the trigger pull.

Jim
 
Possible Cure

FYI I talked to EMF's gunsmith and I think he's hit on the problem. Something I hadn't noticed. Thankfully fairly minor. There is a ridge of metal around the blast shield where the firing pin exits. This was caused while drilling the hole during manufacture. The floating firing pin just pushed the metal out after a few hammer strokes. As the cartridge is slammed backwards during firing this ridge holds the primer slightly proud of the frame causing some metal to migrate. Of course then the cylinder won't turn on its own. I can see the outline of the ridge on all the cartridge primers, some just more than others. I'm going to smooth the area out and I'll bet that cures the problem. At least here's hoping!
 
Sound like the hole was drilled too small and the firing pin expanded it, pushing out the extra metal. If that is the problem filing off the little burr should solve the problem.

Jim
 
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