Need help getting my 9 mm Commander to run with my Infinity

[jjmoberg]

I have a 9 mm Commander 1911 that I cant make run right with my Infinity on it. It has an 18 lb hammer spring and an 8 lb variable rate Wolff recoil spring in it. The gun runs fine with +P defense rounds and a 14 or 16 lb recoil spring and no can. It will run standard 115 gr or 147 gr loads with a 12 lb recoil spring and no can. I cant get it to cycle more than 2 rounds consecutively after the first magazine with the can on and the 8 lb recoil spring. It seems to always feed fine for 4 or 5 rounds, or even a full mag, when shot cold, then gets worse. It will either stovepipe or totally short stroke and not even eject the empty. The slide will come back far enough to reset the hammer, but not far enough to pull out the empty. The gun does tend to eject empties straight up, but that should not have anything to do with it short stroking. I suppose I should try some +P defense rounds through the can, just to see if it will cycle with the can on at all.

Should I try a lighter hammer spring?? The gun seems pretty hard to get the slide going by hand with the hammer down, and then slides like nothing else...

Is it possible the piston is sprung incorrectly, or the piston fits in the bore too tightly? It seems as if the piston is pretty tight inside it's little housing... I have cleaned and lubed the piston assembly, and the gun....

Thanks,

Jeremy