What Glock do I buy? ...What conv barrels? I want to shoot .40S&W/10mm and maybe .45ACP. Can I do this with the same gun using a conversion barrel for the Glock 21? Do I have to buy different mags? I reload and cast my own bullets, but have not had any experience with aftermarket barrels/ lead bullets with Glocks. THANKS for any help. Just trying to think it out before I spend my hard earned money. NewB from Tennessee.