Especially with 300 mags. Those are made with more clearance at the front rib for loading heavy subsonic bullets longer without pigeon toe.

There isn’t a 300 magazine that I know of with a rib at the case shoulder to prevent a short OAL round from moving forward. I don’t know if that’s because nobody making mags understands this or if there isn’t enough shoulder on the 300 for a rib to work.

The best solution at this time is to use ammo with the longer 300 specific bullets loaded to mag length. Like black tip.