I just bought a new Ruger 223 and have experienced the same issue with the magazines. The last round slides forward then drops down into the magazine. It has nothing to do with type of ammo or length of the ammo, the Rifle or the Bolt. You can duplicate this issue just moving a single round forward in the magazine with your finger and watch the back of the round drop off the plastic rear shelf of the magazine down into the magazine. The bolt then hits it in the sade of the round. Ruger sent me three that still do not work. They "claim" they have range tested magazines that work. We shall see when they arrive. But you are correct, why did they release a weapon that has a known malfunction? Getting Ruger to admit this issue is nearly impossible. The person I talked to said they only had a couple phone calls about this.Then finally admitted they were working on it and would send me range tested magazines.