What exposed lead does when tampered with is destroy the ballistic properties of the shape and create inaccuracy. Kids doctoring bullets on the battlefield with ignorant pet theories isn't the best place for it to happen.
Since the 1940's, most actions have been self loading - and that has had a bigger effect on bullet design than recognized. What happens when the bolt strips the cartridge from the magazine is that the bullet frequently contacts a loading ramp that has only be factory machined - not hand polished - and controlled feed isn't happening. It's a like hitting it with a hammer and then pounding it into battery with the bolt face. The bullet needs a jacket to protect it - or the buildup of shavings from being scraped would eventually add to jamming the action.
There is also the unreasonable and entirely preposterous notion the Army continues to foster that bullets fired from combat weapons might need to penetrate something other than human flesh. Like, anything in between - dirt berms, logs, sand bags, solid core doors, adobe, light frame construction, sheet metal automobiles, magazine carriers, or body armor.
Open tip and hollow point bullets don't do well with any of that, they expand much too soon and dump all the energy into the barrier material, and then fail to penetrate the enemy standing behind it.
The Army doesn't need or want a bullet that flattens out and creates superficial or even cosmetic damage when it impacts something a lot tougher than a human ribcage - like, say, a chest harness filled with double stacked AK mags. So they plan to stick with a jacketed bullet that can fragment and do it all - be shock loaded into a an automatic weapons breech, penetrate intermediate barriers, and then create enough wound to stop an enemy from firing back - in a 2MOA window.
There's a lot more to it than deer hunting or a trip to the target range.
