Last night I took the PSA Rock to an indoor range along with 100 rounds of ammunition, one box each of American Eagle 40 grain FMJ and AAC 40 grain VMAX.
Out of deference to range rules each magazine was loaded to only 10 rounds. The cartridges loaded easily into the magazines without the use of a loader. Loading them to full capacity may be easier with one, however.
It's worth noting that the magazines are of the double-stack, double-feed type, like AR15 magazines. To load you simply press the rounds straight down into the mag.
I shot the American Eagle ammunition first, and experienced no malfunctions. The AAC ammo was loaded noticeably hotter with a bit more muzzle flash.
Speaking of which, the gun was not as loud as I was expecting. Certainly, it has more blast and flash than a .22 or the .32 S&W Long ammo I shot in my Colt Police Positive afterwards, but it wasn't objectionable. I found it less obnoxious on the indoor range than some .40 S&W and .45 ACP I've been exposed to.
As expected, recoil was extremely light even with the hotter AAC ammunition.
There were two malfunctions with the AAC ammunition. In both cases the slide locked back prematurely with one round left in the magazine. It's possible that this was shooter-induced. I need to shoot it some more and pay more attention to which magazine I was using when the malfunctions occurred.
All cases ejected vigorously to about 4 or 5 o'clock.
I was shooting at 7 yards and kept my rounds within a few inches. The gun's heavy trigger pull makes shooting tight groups challenging. I am hoping that with another couple hundred rounds it will improve somewhat but it may need a trigger job.
I won't make a final judgement on the pistol until I have 500 rounds through it, but my initial impression remains favorable.