What is your intent to do with it? I have heard the PLR-16 to be finicky for the first couple hundred rounds but to end up ok. AR pistol would be ok, and I've heard good things about the draco..
But to be honest I'd just get a hand gun, and get an AR-15 in its entirety at a later date.
call me a fool, cuz I'm kinda new to the pistol scene, but when I think high-caliber, I'm not thinking 7.62 NATO... I'm thinking .45 ACP or .50 mag... someone please explain what is meant by "high caliber pistol"