My 10mm GP 100 Experience...

[44Blam]

Supposition,is your chamber set up so that only the 10mm cases have something to stop against?. The 40 S&W cases being considerably shorter and no stop have all that energy pushing the cases further into the chamber and even if you do manage get a few to go off all that energy is being wasted on the 40S&W cases getting pushed further into the chamber that could be the cause of getting misfires. Firing pin hits the 40S&W case both igniting the primer and pushing the case further into the chamber. Just keep using the 10mm cases and no problems. Frank

Yup. Agreed.
It says "10 mm auto" on the side and that is what it will shoot.

I'll save the 40s for my Glock.

[1006]

I am pretty sure, as others have said, that your head space is off and that is causing the pierced primers. A thicker moon clip will keep the base of the cartridge closer the the breech face as the firing pin strikes the primer. I think your cartridge is being pushed forward by the firing pin before the primer is ignited.

Years ago I shot 100’s of 40S&W in my stock Delta Elite 10mm with 40 S&W mags. The only issue I ever had was a few pierced primers. After getting a 40 barrel installed—no issues.

[RJM52]

The pierced primers are a headspace issue. The hammer hits the transfer bar that then hits the firing pin. Firing pin hits the primer but with a headspace issue it also pushes the cartridge forward....as the powder is igniting. The bullet starts out of the case and the case head is slammed back against to recoil shield fast enough that the firing pin is still protruding and being held in place by the hammer/spring....and the firing pin then pierces the primer...

Same thing used to happen with the Colt 1911 .38 Super semi-autos. Colt cut the chamber to headspace on the tiny case rim instead of the case mouth like the .45 ACP... If the chamber was too sloppy the igniting round would be pushed past the extractor and tiny headspace shelf on the barrel hood and then slam back into the still protruding firing pin...

Since there are some owners who have no problem with the Ranch Products clips and some that do, my guess would be that tolerances of the guns or the clips vary just enough to cause some problems in some guns... TKs are thicker than the Ranch and haven't heard of anyone having problems when using them...

Bob

[44Blam]

The pierced primers are a headspace issue. The hammer hits the transfer bar that then hits the firing pin. Firing pin hits the primer but with a headspace issue it also pushes the cartridge forward....as the powder is igniting. The bullet starts out of the case and the case head is slammed back against to recoil shield fast enough that the firing pin is still protruding and being held in place by the hammer/spring....and the firing pin then pierces the primer...

Same thing used to happen with the Colt 1911 .38 Super semi-autos. Colt cut the chamber to headspace on the tiny case rim instead of the case mouth like the .45 ACP... If the chamber was too sloppy the igniting round would be pushed past the extractor and tiny headspace shelf on the barrel hood and then slam back into the still protruding firing pin...

Since there are some owners who have no problem with the Ranch Products clips and some that do, my guess would be that tolerances of the guns or the clips vary just enough to cause some problems in some guns... TKs are thicker than the Ranch and haven't heard of anyone having problems when using them...

Bob

I got some TK clips specifically for 40 S&W in the GP100. I shot a bunch of 10mm with them and to be honest, I like them better than the Ranch clips...

I have yet to shoot any 40s with them. Maybe when I get bored of other things... Until then, 10mm is 10mm.