I have a USP 45 non tactical model in my possession and an AAC Tirant M suppressor pending since March. I'd like to be able to suppress this thing. My research indicates I'd need a threaded barrel ($250 from Midwayusa) and the correct piston from AAC. I've read some murmurings about changing out the recoil assembly and adding an O ring. Is this true?
Before anyone suggests I sell the non tactical USP and buy a Tactical flavor, I tried. With the condition my pistol is in (LE trade in) I would be lucky to get $450.
I'm also probably going to grab a GGG light rail adapter and throw an X300 on the bottom. Will have to find somewhere to make me a holster.
Thoughts?




Edit: Forgive the potato quality of the picture.






 

From the pictures it looks to be without an oring so you will need one of those. https://www.hkparts.net/shop/pc/HK-Barrel-O-Ring-45-Caliber-Pistols-p296.htm

I'm not sure if the recoil spring assembly is different. I'd try to shoot it and see how it works. But, if the gun has had a hard life like you've mentioned it might not be a bad idea just to replace it anyway.

I added a threaded barrel and the proper O ring for the barrel and mine works fine.

Do the irons work with the can on?

If you index your piston correctly and "shoot through" the can they work fine. If you want to see over it you need suppressor height sights

Even though it's an HK barrel it might require some fitting, just sell it and buy a USP Tactical. Barrels already fitted, sights are good for suppressors and you get the match trigger. Keep it and get the Tactical as a range toy.

barrel is slightly cheaper from HK here

I would just buy the threaded barrel and go to town with it. But to be "correct" you need to replace the recoil rod assembly with the heavier secondary spring to account for backpressure from the TiRant. So you can sell your gun for $450 and add in $450 for a Tactical, used. Or spend $450 to get barrel, recoil rod, pistol, and not have match trigger or suppressor sights.

I've got a USP45 Tac.  It was one of my grail guns, and it shoots amazingly well, and sounds phenomenal suppressed.  

My advice is to save your money, keep the USP you have, and add a Tactical to your stable.  Its probably about as cost effective and much less a pain in the ass than trying to add all the tactical parts to your USP.  I got mine for $500 in rough shape with no case or magazines.  Well, it looked rough until I cleaned it off and now it looks brand new.  Bought three mags and bobs your uncle.  It has made pretty much all other large pistols irrelevant for me.  I run it with a Hybrid, wet, and it sounds like a loud handclap.

The recoil assembly in the USP 45 Tactical is slightly different from the standard. It uses a heavier secondary spring for the increased recoil impulse when suppressed.

I bought an HK barrel and o-ring for mine, and when my can finally gets approved for it, I might just buy the USP Tac recoil assembly (complete) from HKParts to complete it all.