Uploaded September 2016 | Updated September 2026, 2 weeks ago
Note: I have been told that finding aftermarket barrels to ream to 10mm is extremely challenging now. Please research parts availability before getting too excited about this project!
This video is a short overview of how I put together my USP in 10mm. It's a pretty easy and inexpensive process that leaves you with a reliable 10mm handgun and the parts to switch back to 40S&W again easily. Reliability for me has been virtually perfect for me, and while I say at the end that it won't be a defensive piece anymore, I think it would probably be fine for that purpose. Highly recommended if you like the idea of a 10mm HK pistol.
Parts List:
A 126mm STI 2011 magazine in 40S&W. The notch I cut is about 19.5mm down from the top/center of the mag's front surface.
Barrel reamed - I used Van's Gunworks in Sandusky, OH. Good service and not expensive.
18lbs recoil spring from Wolff Gunsprings.
The capacity is 13+1 in this configuration. AMMO THAT RUNS WELL (SO FAR): Buffalo Bore 180gr JHP, Underwood XTP 200gr, HRS Bear Load 200gr, Sig Sauer 180gr, Remington UMC 180gr, Hornady XTP 155gr, Armscor 180gr, and PMC 200gr (had a couple hang-ups with this one).
My full write-up is on HKPro: tinyurl.com/jtpwv4y
If you like USP content, stay tuned for my epic ALL THE USPs review in the near future.
Note: I have been told that finding aftermarket barrels to ream to 10mm is extremely challenging now. Please research parts availability before getting too excited about this project!
This video is a short overview of how I put together my USP in 10mm. It's a pretty easy and inexpensive process that leaves you with a reliable 10mm handgun and the parts to switch back to 40S&W again easily. Reliability for me has been virtually perfect for me, and while I say at the end that it won't be a defensive piece anymore, I think it would probably be fine for that purpose. Highly recommended if you like the idea of a 10mm HK pistol.
Parts List:
A 126mm STI 2011 magazine in 40S&W. The notch I cut is about 19.5mm down from the top/center of the mag's front surface.
Barrel reamed - I used Van's Gunworks in Sandusky, OH. Good service and not expensive.
18lbs recoil spring from Wolff Gunsprings.
The capacity is 13+1 in this configuration. AMMO THAT RUNS WELL (SO FAR): Buffalo Bore 180gr JHP, Underwood XTP 200gr, HRS Bear Load 200gr, Sig Sauer 180gr, Remington UMC 180gr, Hornady XTP 155gr, Armscor 180gr, and PMC 200gr (had a couple hang-ups with this one).
My full write-up is on HKPro: tinyurl.com/jtpwv4y
If you like USP content, stay tuned for my epic ALL THE USPs review in the near future.
