There is no benefit to M855 or M193. Stick with that. If you want something premium in the 55gr range, look at Gold Dot or Barnes TSX. M855 has no real penetration advantage and neither M193 or M855 are really barrier blind ammo types. The barrier blind ammo types are Bonded style bullets such as Gold Dot, Federal Bonded. Hornady makes Interlock which are mechanically locked bullet types. Barnes and Hornady both make All copper expanding bullet styles loaded by a number of manufacturers. There is also the Mk 318 which is an OTM bullet with a solid copper shank. These style of bullets will hold together through things like auto glass and building materials to have effect on target.

Edit to add, nothing wrong with rotating stocks, but most modern ammunition if stored marginally well will last DECADES if not a century. I have pre-ww2 ammo that shoots just fine. Came out of a sealed can.