Had some time yesterday so I headed to the range with the 3914 and a bag of ammo.
It turns out that the extra mags that I had snagged from the bargain bin aren't factory. I think that they are ProMag with replacement red followers. I'll grab a couple more off of Ebay.
So three mags. About 150s rounds fired without a hiccough. Lead conical bullets, FMJ, and hollow point. Looks like the ProMags work.
I have thousands (literally) of NRA 50 ft pistol targets so I use those for everything. Holding in the center of the black, everything stayed in the black at 20 feet.
Moving back to fifty feet, I found that my groups were very respectable when I shot one handed in a bullseye stance. Maybe it is my bullseye background.