uh... wut?
alluminum cased ammo is alluminum for a reason. it's a cost saving material. naturally the ammo using alluminum casings is also going to be loaded lighter to cut down on the amount of powder needed and is going to be lighter projectiles to cut down on the amount of lead and copper needed as well. why are you buying the cheapest stuff on the shelf for defense? that stuff is designed just like all of the white box ammo and steel cased, making holes in paper that's it. defense ammo should expand, FMJs don't expand. you should be buying stuff that comes with brass or nickel casings that should be costing at least double what the cheapest stuff on the rack costs. the difference in price nearly guarantees you expansion, and reliability, but should also be tested thoroughly before you make the decision to carry that for defense.