I bought this gun for my son and the sole reason was to install the slide fire stock. I've been chasing a number of issues but the last two (maybe one or the other) seem to solved it. I hope.
I did machine the head of the firing pin as posted above. It does protrude farther and makes a deeper impact on the rim. I have a Timney trigger and noticed it seemed loose (with KNS pins). I removed it again and installed some steel under the set screws. Tightened it all up and tried it out again.
Just ran through 3 mags non stop (of Mini Mags) which was my/his goal. Hopefully I have this sorted out. Lastly, I have a pretty good inventory of .22 and tried almost everything in this thing so far in this thing. The 36g Mini Mags seem to work best when using the slide fire.
*Interesting to note CCI SV does cycle well when using a supressor.