I don't know what kind of ammo, specifically, that you're using but I would advise against bulk 500+ round ammo if you're having a lot of duds. I have taken the approach that I use CCI Mini-Mags exclusively. Round-nose non-hollow point ammo doesn't mean a whole lot as far as feeding if you're not using truncated cone ammo. All the HP ammo in the bulk packs are essentially round-nose ammo with a dimple. Clean the gun thorougly, and you should really be able to shoot any round-nose hollow point or solid-point ammo with high reliability. The Model 60s seem to be very picky about grit that builds up in the bolt area and then they start to jam. The good thing is that the Model 60s seem much more accurate than a 10/22 for example, but tend to need much more cleaning. Good luck with that M60 and keep shooting!