I have a Foxtrot Mike's Glock mag lower ready for the .45 (8oz buffer, .308 carbine spring)
I have an Aero large caliber upper on the way, along with a 16" KAK barrel. That barrel will get cut and re-threaded (5/8-24) locally, but I haven't decided on finished barrel length yet... not longer than 10", nor shorter than 8" is where I'm at right now.