I have recently become very interested in starting a ar45 build. Having trouble deciding what lower to start with and was wondering if anyone had any experience and/or advice on the issue. Or a link to a thread on the topic. I know I want a dedicated lower but I don't now if I want it to take glock, grease gun or Uzi mags. I imagine that Uzi and grease gun mags might be cheaper but to my knowledge the lowers that take them don't hold the bolt open after the last round is fired but the glock ones do. Can anyone point me in the right direction on this? I'd like cheap mags but I'll pay more if one functions much better then the other. Thanks