Converting 1911 from 9mm to .40 Call


Mac Attack
September 9, 2003, 04:45 PM
I recently acquired a mint condition Colt Series 70 Combat Commander in 9mm for a ridiculous price. I wanted to know if it is possible to convert my 9mm to a .40 cal by changing various parts? Interested in your input.


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Walt Sherrill
September 9, 2003, 04:50 PM

But you'd probably need to replace the entire top end -- as the .40 round requires a different barrel, extractor and slide (for the different headspace and breechface...) It might be almost as cheap to buy a .40.

Just shoot the 9mm... or talk to me about trading it for a very nice Cylinder & Slide-tuned (trigger and reliabilty work, but not the full C&S magic) S&W 4006 that I picked up a while ago.

September 9, 2003, 04:55 PM
You need a full top end (slide, barrel, etc). I did that on my STI 9mm 1911, but for a production grade 1911, the inherent cost of fitting the slide and barrel will put the cost of the new top end above the price of a whole new gun.

September 9, 2003, 05:04 PM
Need magazine and also ejector on frame, IIRC.

Mac Attack
September 9, 2003, 06:00 PM
I always thought that the only requirements to convert a 9mm to a .40 were to change the barrel and magazines and maybe the extractor. Boy was I off! :what: :eek:

I think for all the trouble of purchasing and fitting a new upper that I would be better suited to purchase a new gun outright. Thanks for the info guys.


September 9, 2003, 06:11 PM
Yep, new top end, since the .40 round has a larger diameter rim, and magazines. Expect to spend a few hundered on such a project.

Walt Sherrill
September 9, 2003, 06:18 PM
Kinda depends on the gun.

And you can generally MOVE DOWN in caliber, but seldom up. (Witnesses are one exception.)

With some guns, like SIGs and maybe Berettas, all you need is a special Bar-Sto barrel which makes it all work together. (Bar-Sto can adjust the barrel so that headspace isn't a problem, the round works with the .40 extractor, etc.) I know of several folks who have done this.

With Witness small frame guns, all you need is a different factory barrel. (The mags are generally interchangeable -- as it the case with many guns.) But the Witness guns are designed this way, from the start. The 9mm and .40 have the same barrel diameter, for example, which would not be the case with most guns.

With a 1911, however, you've gotten into a different world.

Jim Watson
September 9, 2003, 10:01 PM
Some of the early 10mm 1911s, pre Delta Elite, were built on .38 Super slides with the breechface widened slightly and the extractor adjusted. I don't see why that wouldn't work on 9mm to .40. In fact, C&S once sold a bunch of 9mm/.38 Commander slides, opened up to 10/.40 for a few bucks extra.

I don't know if it would still work with 9mm like the European guns do.

And you have to find the right 'smith who knows how.

September 10, 2003, 01:00 AM
Canm easily go from a Kimber 40SW Custom to a $250 Nowlin 10mm ramped barrel and some Wolff recoil rod/springs.

But not from 9mm to 40 cal - the frame and slide are just not designed for the greater pressure.

Sure, you can "rig" it but get a 10mm 1911 and just grab a 40 cal barrle for the easist most reliable swap!

Andrew Wyatt
September 10, 2003, 01:21 AM
But not from 9mm to 40 cal - the frame and slide are just not designed for the greater pressure.

uuh, it's a 1911. the frame is unchanged from the original .45 ACP in metallurgy or design. (except for the ejector)

most you'd need is a new barrel and slide assembly. you can do the fitting yourself, if there is any to be done.

September 10, 2003, 08:06 AM
easy..just need slide and barrel. some new springs..could get away with same ejector and extractor..might need some tweaking..if you are interested in selling your top or PM me..I;d be interested in the commander top end..

for your slide and barrel..look at caspian for slide and lot of choices for barrels


September 10, 2003, 06:44 PM
FWIW: you can use the same ejector between 9mm and ,40. In fact, you can use the same entire receiver including slide stop. I do it all the time. I have a .40 top end that was built up to drop onto the receiver of my 9mm 1911 (STI Trojan). Nothing changes in the receiver. Just top end and magazines. In general, the 9mm and .40 slide stop are different, but you can get one to work for both.

September 10, 2003, 07:08 PM
A little OT: Would requirements be similar to convert a 45acp to maybe a 10mm or 40SW? I mean only the top needs to be changed? :confused:

September 11, 2003, 06:18 AM
It is possible to convert a 45ACP to 10mm with a new top end and magazines. The 45 slide stop may or may not engage the magazine follower, so the slide stop may need to be changed as well. The 45 ejector will probably work ok. The frame feedramp in the 45 is cut a little deeper than in 9mm, 38Super, or 10mm frames, so reliability could be an issue, but then again, it may work just fine.

September 11, 2003, 01:04 PM
Why would you want to? If you want more power, you're better off converting to 9x23. You can still shoot 9mm after the conversion.

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