As we are striving for the smallest lightest micro pistols why does SD ammo have to be brass cased? I have a few boxes of Aluminum cased ammo and it is considerably lighter than brass. It would seem to me that a p365 with 12 rounds of aluminum cased ammo would be a lot lighter than brass. Maybe SD is available in Aluminum but I have never seen or heard of it. If not what makes Aluminum unsuitable for SD ammo?