you would think that after 40 or so years of gun games, you would have the cognitive ability to seat the magazine in a pistol, but noooo.... anyway, shot well enough to get a B card in both RFPI and RFPO with the MK IV... I haven't shot the AR9 PCC since Covid, so stuck the spare 510 on it and will give it a try... some of the primers I loaned out are being replaced so will see if I can remember how to pull the handle on the S1050...ordered a couple of short 4-40 flathead cap screws and will stick the 507 on the G17 slide that was cut for the RMR (same footprint)and possibly give Carry Optics a try.... a Happy Thanksgiving and Merry Christmas, and wishes for a healthy and prosperous New Year to all... regards Les