The issue here, of course, is use of cheap, military surplus ammunition. The answer, of course, is yes, why not? AP ammunition is generally less lethal as it leaves a much smaller wound cavity. It's not magic and it's not something that needs to be regulated, yet. At least, in my opinion. I would include the availability of AP ammo for pistols since the same argument applies except to a greater degree: AP ammo in pistols is even less effective than it is in rifles, and as mentioned that's already less lethal.