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Thread: USP .40 to 9mm conversion?

  1. #1
    Junior Member

    Join Date : May 2008
    Posts : 8

    Default USP .40 to 9mm conversion?


    I have a USP fullsize stainless .40 and was wondering if there is a 9mm conversion kit available. If so, is it just a barrel swap, or are there other modifications needed? How is the reliability from what you have seen/heard? Where can I get it if it is available?

    Thanks a lot.
    HK USP .40
    Springfield XD Subcompact .40
    Ruger LCP

  2. #2

    Join Date : Feb 2005
    Location : SF Bay Area, CA
    Age : 32
    Posts : 71


    You probably need to switch the recoil spring and you'd have to have a barrel that was thicker at the slide area. Jarvis might be able to work something up for you.

    Otherwise, if you find someone who KB'd their bottom end you may be able to buy a complete 9mm slide from someone. The frames are teh same between the two guns.
    HK Mark 23, HK USP 45, Ruger Single Six, Ruger 10/22 (custom stock, trigger) Mosin Nagant (M38, M44, M91/30), Rem 870 Express, 2 AR-15s (M4 style and a 22 build)

    HK USP 45c, HK45

  3. #3
    Unrepentant HKHolic
    Big Bore's Avatar
    Join Date : Jan 2002
    Location : Finally back in Indiana!
    Posts : 10,816


    To do it and have the pistol as reliable as you are use to you need a new barrel, recoil spring, and most importantly, a slide. And by that time you will have spent more than a new pistol costs. HK will not sell just the slide because they are a direct replacement/exchange only.
    You will need the slide because the head size of the 40 and 9mm are different and the 9mm will slip the extractor fairly often (God I wish I had a nickel for every time I've typed that) and your reliable HK will be no more reliable than a High Point.
    If you want a 9mm, buy a 9mm. Trying to make a .40 shoot with 9mm is a money losing proposition in the HK series.

    And buying a KBed pistol just does not sound like a wise move to me, but hey, it's your eyes and fingers. If something KBed the bottom half, how much damage was done to the top half even if none is apparent?
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  4. #4
    Junior Member

    Join Date : May 2008
    Posts : 8


    Makes sense. Thanks guys. I'll just keep her stock and get a new 9mm.

  5. #5
    Senior Member
    halo2304's Avatar
    Join Date : Jun 2006
    Location : Maine
    Posts : 119

    Default I'm lookin' to hit the trifecta!

    Sorry if I'm hijacking this thread but it sounds like FITW got his question answered and since my question is very goes nothing!

    I recently bought a USPc in 40S&W and it came with a 357Sig barrel. I was wondering if I could just buy a 9mm compact barrel and use it for plinking and practice? I know it won't be reliable and I know that the 9mm is slightly smaller (by 1mm!) than the 40/357 but I don't really care as long as it's not going to damage the gun.

    I know that the USP series was originally designed around the 40S&W and was "scaled down" for the 9mm. This would lead me to believe the barrel outside diameters are the same and I don't think the 9mm would hurt the 40S&W. Also, from what I've gathered from looking at USP spare parts, the extractors are the same for the 9/40/357 guns.

    What about a "conversion" barrel from IGB or someone?

  6. #6

    Join Date : Apr 2008
    Location : Little Rock, Arkansas
    Posts : 81


    I found this website that appears to sell 9mm barrels for USP .40's. Got the link from another thread here. I'm not sure how well it works, but I am curious to know the results if anyone has tried it.

  7. #7
    Unrepentant HKHolic
    jeray's Avatar
    Join Date : Oct 2003
    Location : Kentucky, US
    Posts : 4,336


    Yes, Has anybody used these conversion barrels?
    Yeah man, I tell ya what, man, them dang olí HKs, man, talkin' bout SUH-WEET, man, dang ol' point and click, baby, just, just, dang ol' awesome, man.

  8. #8
    Unrepentant HKHolic
    Big Bore's Avatar
    Join Date : Jan 2002
    Location : Finally back in Indiana!
    Posts : 10,816


    They work until the extractor gets worn then it starts slipping the rim of the 9mm case because the bolt face of the .40 is bigger than the head of the 9mm. A few thousandths is not much but the gun will usually not be 100% reliable when using 9mm. That is the way it normally happens. I have not heard anyone say that this conversion has worked out long term for them first hand. It is always a second cousin's girlfriend's uncle's step-son who claims 100% reliability.
    Try it, if it works let us know. If it doesn't, let us know that too. This topic comes up dozens of times each year.

  9. #9
    Unrepentant HKHolic
    Kost's Avatar
    Join Date : Oct 2006
    Location : USA
    Posts : 4,730


    Pssstttt - any conversion from .40sw to 9mm or vise versa needs a complete top end - slide/barrel of whatever caliber, in any pistol, not just HK, there are standards, the two calibers are very different size in OAL/breech face dimensions/SAMMI CUP pressures.

    9mm +P operates at approx 38,500 pounds of pressure per square inch, plenty of power to destroy a pistol,
    2 hands, and a human face in a flash, when saddled up with a .40sw slide.

    Do your home work/research and do your conversion/s per Firearms Industry Standards/SAMMI using spec'd parts for your caliber...a simple barrel swap wont cut it in a caliber conversion 99% of the time...remember breech face/chamber dimensions?
    The Spirit of God hath made me, the breath of the Almighty hath given me life

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