I really wanted to use UMP mags in my USC but not crazy about doing a full UMP conversion. Well Tbostic is fixing up these USC lowers where they will accept UMP mags and he also takes the USC stock and reforms it to look more like a UMP stock. I decided to go that way, and I have to say...it's pretty cool. I still had to make it compliant so I went with a US made sear and mag parts. I transferred all my lower FCG parts last night and modified the upper magwell. Now I'm dying to go shoot it.