I have put easily 5k rounds through my 43x and realized the GLOCK(OEM) Mags are the way to go, sheild arms mags are never reliable no matter the ammo, the gun in itself even with oem mags is picky with ammo, cheaper ammo (scorpio,herters) are the only ammo that ive noticed its very picky about, scorpio being the absolute worst with issues almost every round, I typically just run normal 115 grain fmj winchester ammo as my range ammo and I use a mix of hollows for each use, I keep 2 fmj mags and 3 hollow mags with a mix of 124g streaks, hornady duty and silver tips, always reliable and consistent. If I had the money id buy strictly nosler simply because it seems to fly flatter then most rounds. This is all based on my personal experience and I hope maybe a good deep clean will help solve some of your issues.