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Just inherited an HK USP 9mm. Can this be converted into a .40S&W? Thanks.
First -- Congrats on picking up an HK. Good pistols. :rock:

Second -- Why in the world do you want to change it to .40 S&W ?

9mm is GTG. No reason to change it to .40 imo.
 

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I don't think you would want to do that. If you look at HK's site they have in the FAQ-" Can I change ___ to ___" and all they say is; HK does not authorize... blah, blah, blah. I would think if it were a 357sig to 40 you would probably be ok (it's no problem with a Glock) but I'm gonna have to say no, don't mess with it. I'm not a gun smith though, so maybe one of them will tell you otherwise. And besides, the USP in 9mm is a great pistol.

I put a pic of my NP3'd USP just because threads are better with pictures.
Good Luck
View attachment 45895
 

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I'm a .45 guy who doesn't trust the 9mm. :)
Well good luck to you my friend.

.40 S&W is a very far cry from .45 acp.

Just sell your pistol and get a .45 acp -- pretty simple eh?
 

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I don't think the USP 9mm is convertible to .40. The .40 can be converted to 9mm, but not the other way around (breach face too narrow, ejector, extractor, etc...)
 

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Discussion Starter · #7 ·
Thanks everyone. I'll check out the HK USP 9mm. Also getting a few other firearms. Yes, can always sell them and pick up a CMP Carbine (wouldn't mind another piece of history). My three 1911s are all that I need in sidearms right now.
 

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You can but probably need too many parts to make it worthwhile. You would need a slide, barrel, and recoil spring for sure. I'd guess you could open up the breechface on the 9mm slide a bit if you wanted to but that would ruin any resale value. The USP .40 was the first commercial purpose-built .40 that was later scaled down to 9mm. Until the USP, all .40's on the market were scaled up 9's. So from a strength standpoint you are good to go (same frame for the USP .40 and 9).

I'd vote you should keep it 9mm for practice or trade/sell it for a USP .40 or .45.

Nice guns, light recoil, tough finish.
 

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I don't think so. I bought a USP45 back when they first came out. There was talk back then that the .40 and .45 shared the same frame, and that it was much stouter than the 9mm frame. Meaning: 9mm frame isn't strong enough to support the .40 S&W battering.
 

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Enjoy the 9mm. It's a great shooter. Then go out and buy the same gun in .45 ACP and enjoy it. And then say, hmmmmmm. Both guns are great, I wonder what the .40 S & W feels like, especially since I am familiar with the 9mm and the .45. When you own all three, you will definitely have a smile on your face.

Then go out and buy a government size 1911. And then try an Officers ACP 1911. Then you will have to try one of the sub-compact.

And so forth and so on until you realize that you are an addict. And you are hooked but it feels so good. Soon you will be haunting gun shows looking for an ammo fix...new...reloads...any loads. Got to go shoot.
 

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Just leave it be. These are great shooters, reliable and accurate.
I purchased one for my wife.
I am so amazed at how clean it stays. She ran over 800 rounds through it during our 4 day Front Sight class. I swear it seams the only thing that was dirty was the barrel. My 1911s seem to puke in them selfs and everything is dirty.
 

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I don't think so. I bought a USP45 back when they first came out. There was talk back then that the .40 and .45 shared the same frame, and that it was much stouter than the 9mm frame. Meaning: 9mm frame isn't strong enough to support the .40 S&W battering.
Nope, 9 and .40 have the same frame, .45 frame is a tad larger and stronger.

Still I would think it is not cost effective to change a 9mm to .40. Too many parts to switch out. But the original poster asked if it could be done, not if it was practical.
 

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My USP45 slide is 14 oz and the USP9 slide is 12 oz, that is too light sounding for a full size 40 slide. Just for the heck of it I tried to fit a 40 cartridge under the extractor and the breechface cutout is purely a 9mm. I like my USP9, it is specifically okayed for use with +P+ ammunition including the RA9TA 127 +P+.
 
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