In the interest of full coverage there are other PCCs that can utilize M&P mags.
Kel-Tec Sub 2K multi-mag version. I almost bought the MCarbo version of this before I got my first Ruger PCC, with the folding mount for an optic and a couple of other addons it gets over $1,000.
Just Right Carbines, finding the M&P version in stock can be hard.
I've never owned either and I believe that there are others.
Here is some info about the PCCs used in steel challenge:
Here’s a look at the changes occurring in this evolving division. PCC continues to grow in popularity—44 percent of the shooters at the 2020 USPSA Nationals were first-time attendees.
www.ssusa.org
If you want info on how blowback 9mm rifles work and tuning them for reduced recoil check out:
No-BS information for the 9mm AR.
blowback9.wordpress.com
The info is geared toward AR9 style rifles, but is worth reading if you want to get a handle on direct blowback operation.
The really fast guys don't use Ruger PC Carbines and I'm the only person I've seen with an FPC, so far. I shot three rifles at my match yesterday, a Ruger PC Carbine with iron sights, a Ruger 10/22 with iron sights and the FPC with a Holosun 510c red dot. The total money I have in all three of those is just about the same as the PCC that another shooter was using. I'm not a top level competitor, just a guy who shoots to have fun.