I got back to the indoor range this morning. (The second range trip since receiving my MC9 back from Century Arms with a new RSA.)

TWO failures in the first 20 rounds: failure to feed (round nose caught on the bottom edge of the feed ramp) and failure to fire (pulled the trigger, click and no bang...no primer strike either.) I had another failure to feed (same thing as before) later in the range session.

So, THREE failures in about 125ish rounds of 124g round nose = not pleased. I'll clean the gun and mags really well and try again, but I'm very dissatisfied with this MC9.

(My SFx ran beautifully to end my range session. Not a single hiccup or failure to be had from this gun...ever.)

Sorry to hear that...hopefully it works out .

Seriously, I hope it all works! Keep banging away! Is it really a RSA change and an extractor spring?
If you can get another extractor spring, I'd grind a coil off (or 2) and see how it performs.