Is it possible to convert a .40 S&W to 10mm?


April 18, 2003, 01:17 AM
Is it possible to convert a gun like a Glock 22 or HK USP to 10mm with a drop-in barrel and a fatty recoil spring?

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April 18, 2003, 01:21 AM
Not in the case of the Glock. Rounds wont fit in the mag. And the G20 mag won't fit in the G22. If you happened to have a 1911 chambered in 40S&W, then with a bit of work, it should be possible but would be more financially sound to just sell it and buy a 10mm chambered 1911 unless you were wanting to build a really special keep-it-forever type gun.

Porter Rockwell
April 18, 2003, 03:07 AM
Hello Justin,
NO with the G-22, what cratz2 said.
The 1911 of course is the correct mag length and Colt once offered a switch barrel .40S&W/10mm
The full sized H&K USP-40 can and has been rechambered for the 10mm, too bad H&K can't keep up with the customizers!

Big Daddy
April 18, 2003, 12:20 PM
HK USP40F can be converted to 10mm. I did one :D

You need to use Para P16 or SVI mags, modify the baseplate, cut a mag catch notch, ream the barrel to 10mm, open the ejection port to clear a live round, and you CAN change the recoil spring to a heavier one (I did, but others left it stock).

Also, if you don't want to ream your stock barrel Barsto will make a 10mm USP40F barrel for you. I think they quoted me $200. In hindsight, I should have bought the barrel and kept the stock one as a .40 for a dual caliber gun, but I didn't.

Also, I think the SVI mags will allow a slightly longer OAL than the P16 mags.

April 18, 2003, 01:13 PM
Big Daddy-
I think I'd just opt to order one from Bar Sto as attempting to make my own would result in hilarity.

What's the deal with the magazines? Why do you have to do the switch?

Porter Rockwell
April 18, 2003, 01:52 PM
the 10mm is a longer cartridge than the .40S&W. The H&K mags are thick and will not accomadate the longer 10mm, the Para P-16 mag will hold most (not all) 10mm ammo that doesn't exceed 1.255OAL
Read Joshs post again, the ejection port needs to be machined longer/larger as well.

April 18, 2003, 03:56 PM
as far as Glock goes, why not just buy a 10mm Glock? they make 'em ya know... no need for conversions. USP would make a great platform for 10mm, but its seems like it would be kind of a pain in the keister and i would worry about reliability, escecially if i did it myself! the really hot .40 loads and the .357 sig offer good, but not quite as potent alternatives to the 10mm in a USP.


April 19, 2003, 12:41 AM
Alright, I've heard so much about these conversions with the USP, and I have three questions.

One, how do you put a heavier spring in an USP? I'm looking at my recoil spring right now and its this captive dual spring jobbie, that, number one, I have no clue how to take apart, and number two, I have no idea where to get proper length/weight spring from.

Two, what is the SAAMI spec OAL for 10mm? If it is smaller than/equal to what you can do with the Para or SVI/STI mags, great! If not, how much shorter are we looking at? A length equal to a .40 S+W? That would not be so cool.

Is there a gunsmith out there doing these things? If so, how would I get in touch with him? Making it reliably feed, extract, and eject fired 10mm out of a .40 gun is something that I would
to see before plunking down any cash.

April 19, 2003, 02:50 AM
No, but it is possible to convert the 10mm Glock to .40!! I've done it!! :D

Porter Rockwell
April 19, 2003, 04:18 AM
1. Wolf Springs
2. 1.260 (Rem.-WW.-PMC are fine in Para magazines
3. Any competent smith can do the conversion in an hour shop time.
4. Function problems in an H&K? You're kidding right?
Nobody here is asking you to spend any money Bergeron, Justin asked about conversions.

April 20, 2003, 02:43 AM
I know that they're not, it's the little voice in the back of head that wants me to.

I would still be interested in any first hand experience anyone has with the conversions.

April 20, 2003, 08:15 AM
It's an Alaskan thing...

(No rap on Alaska or Alaskans :) )

Check over on Do a Search for a poster named "Monte." IIRC, he posted in detail there about converting a full-size .40 USP to 10mm. It might have been in the 10mm-subgroup on that board.

In addition to what's been mentioned, I believe this included swapping out the .40's plastic mag-release catch unit for the .45 USP's all-steel unit. Also, there was some small mod done to the mag catch hole on the Para .40 mags, so they would lock-in securely.

Apparently this all worked fine, and he's got a tight shootin' 10mm USP. As I recall, he even commented that the USP's sights shot to POA w/ the 10mm.

Works for me. :cool:

April 20, 2003, 03:44 PM
Man, a USP compact in 10mm would be sweet.


I wonder...

April 20, 2003, 08:33 PM
I saw an Expert .40 the other day that was begging, I mean begging, to become a 10mm!

Whenever the USP 10mm threads come, they always seem to get a very positive response, perhaps we should collectively contact HK about this?

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