Oct 15 New Gun Pr0n (Updated)

Just got back from Diamondback Police Supply with my re-retirement present, a slightly used Rock River Arms LAR-15 converted to 9-mm (it was built on a receiver marked 5.56-mm). The previous owner threw in eight magazines of various size with it. He claimed it was finicky on ammo and didn't like the cheap Winchester whitebox stuff he was feeding it. Here's hoping that the case of Wolf 9-mm I have left over from last year's Ammo Day fits the bill. If not, maybe that case of Greek stuff I got for Xmas will be okay. So much ammo, so little time to shoot it. Ya know, if I got off the darned computer once in a while....

Update: I guess he should have said "finicky with ALL ammo." I got jams (failures to eject) or every second shot out of every magazine but one. This mag, the longest, functioned perfectly every time, except for the last shot. I tried this several times with three different brands of ammo--same result. Methinks Cowboy Blob has been had, but I'm not sure what my options are. I can't prove there's anything wrong with the gun...the magazines seem to be the problem. Any ideas?