HK UMP conversion by TommyBuilt Tactical

Early 2016 was a buying frenzy for me. I was doing my last push before 41F became effective. I'd just crossed the threshold into the world of HK polymer rifles with my XM8 project. I was looking for 45 caliber subguns. Hmmm, seems like there is a natural cross of those traits -- the HK UMP. I decided I better get into it while the getting was good. It starts with an HK USC. That's HK's non-governmental civilian version of their UMP. It utilizes the same operating platform with some changes to not be fully automatic or readily convertible to that state. HK stopped importing them, so over time the availability has gone down and prices have risen. There were 2 colors released: grey and black. The black commands a higher premium due to a lower volume imported and higher demand (for a few reasons). I was starting to stretch the wallet a bit thin, so my plan was to acquire what I could and file a Form 1. Then finish the conversion at a later date as more funding became available. I'm horrible about starting projects and letting them languish, but this one I was at least honest with myself about. I quickly found a USC on gunbroker and purchased it. I had a Form 1 submitted for it the same day I brought it home.

Five months later, the Form 1 came back approved. Meanwhile I kept a lookout for conversion parts. The major decision left was how to do the conversion. There really are 2 primary avenues of conversion: a fuse job or a multitude of stock blocks. The fuse job leads to the most accurate conversion (in terms of a semi-auto clone of the UMP in all dimensions), but the stock block conversions are still quite good. It varies a bit, but they add half an in to an inch in overall length due to how the back of the USC receiver is. I decided to go with the fuse job that Tom Bostic / TommyBuilt Tactical does. That requires a usable rear stub from a de-mil'd UMP. Eventually I found one as a part of a set I think someone else had gathered for a similar conversion. I assume they changed their mind. That made it easy for me. And so those parts set, even after I had the approved Form 1 back.

Fast forward another 5 months. I'm up at the gun shop. I forget why I was there (probably another transfer) and they tell me they got something else in from Tom for a Form 4 transfer to another customer. This is a small town, so that's kind of amazing. They pulled out of the store room a small (for a rifle) Pelican case and pop it open for me. There sits a beautiful fuse job UMP conversion in a custom cut case. Well that lit fire under me. I immediately reached out to Tom for a price quote and to see if he had room in the schedule for it. I really like the various colors I've had Tom do and I have seen a lot of pictures of his work in a rainbow of other colors or color combinations. So I asked about that too. Someone in my mind I had it set that the USC I acquired was the grey variation and so it would need refinishing anyway. Might as well pick a snazzy color. When I went to actually pull it out of the back of the safe to pack up and ship to Tom I discovered it was black. So I cancelled the fancy paint job and went with standard black. I requested the full package conversion with one small variation -- a threaded barrel instead of the UMP flange. For the practical reason of sharing my 45 suppressors among hosts it's nice if they all have the same thread. In this case that's M16x1LH.

Tom Bostic does quality work. Have no doubt he'll do what he claims he can do and do it well. His reputation is stellar and well earned. I've heard of very few quality concerns, questions, or problems with his conversions. What you also rarely hear about is just how fast he is. I'm astounded at how quickly he turns work around. I've done projects with quite a number of gunsmiths. Some big projects; some small projects. With those have come some variations in quality and how long it takes. Tom doesn't mess around. He turned around this project so quickly that I had it back in-hand a week to the day after I shipped it to him. I've had occasions where just the shipping to Tom took longer than that. And there wasn't any expedited shipping on this one. Amazing. In comparsion, as I write this, I have a project that has been at a gunsmith for 22 months.

Suffice it to say, I'm impressed. I'm unable to see where the receiver is fused to the UMP stub. Everything feels like it was originally built like this. Everything fits tight. I'm impressed at how handy the rifle is. It's lighter than I expected. Stock length and comb height seem purpose built for my frame. I added the top and bottom picatinny rails, along with an HK vertical fore grip on the bottom rail. It's very comfortable to hold. On a suggestion from the CZ forums, I added a Trijicon RMR with a low mount meant for the CZ Scorpion EVO from CZ Custom. I'm quite impressed. The only negative is that it isn't QD. If this was going to be a fighting carbine, maybe that'd be a problem, but it's a range toy, so no worries. Setup with my Octane 45 threaded on, this is an outstanding feeling setup. I just need to get it to the range.