Mine shoots little bitty groups with factory Fiocchi 50 gr V-Max. It’s a bunch of fun for the money.
I ditch the factory P-Mags in everything now. After taking advice from guys on here, I use the stainless ASC mags only. Their top notch. I had some issues with PMags recently and no longer have any faith in them.
Not a fan of the PMag either. Loading it, it was constantly wanting to spread apart and wedge two cartridges SxS. Seemed to feed alright though. I had picked up a stack of Brownells 20rnd'ers that worked great.
These I think:
https://www.brownells.com/magazines/rifle-magazines/magazines/ar-15-20rd-magazine-ss-223-5-56-prod71748.aspx?avs%7cCapacity_1=20-Round
Granted, My experience with AR's is next to nill.