I like the concept in general but am thinking 9mm. Doesn't have the range but up close penetrates better . If I loved my Glock 19 more I would already have one that uses hi cap Glock mags. Palmeto makes them and they are priced right. Saint has nicer furniture but AR parts swap are easy. I've never had a Springfield Armory anything that I didn't like. Can't imagine their ARs aren't quality firearms.

PS I have a Glock so when I'm teaching folks to shoot I can show them that option and show / tell them why I like other pistols better. I admit i wouldnt be helpless if i got into a mess and all i had was a Glock. I just dont like them. Then i pull a S&W revolver out of my range bag and show them what I really like. Heaven forbid if I could only have one handgun and ammo availability wasn't a factor it would be either a M28 or a 44 Mag Mountain Gun (or maybe a 1911)