Just ran across this and I love the idea! Sorry if everyone knows about this but it was new to me and seemed pretty cool!

Basically a carbine upper that attaches to the lower receiver of your glock. No serial numbered parts involved right?

http://mechtechsys.com/#

Hickok45 weighs in too: https://www.youtube.com/watch?v=mwC4M_VInSA

Anyone have any thoughts on these or use one? Looks like it comes in around $500 or so depending what all you get extra.