Conversions question 45------> 10mm and more? [Archive] - Glock Talk


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01-19-2013, 10:00
So there is conversion barrels for 45 to 10mm

If 10 mm can be converted to 40 and 357 sig

Why can't the same company that makes conversion barrels for 45->10mm make 45-40SW and 45->.357 sig and use the G20 mags in my G21SF

01-19-2013, 10:38
Others claim they have successfully used a G29 10mm-40S&W conversion barrel installed in a G30 slide. I archived the post of GT member mpanwar who claimed it works reliably for him. See it here:

Although I haven't tried this personally, it's very possible that the caliber conversion barrels made for the G20 and G29 will function reliably in the G21 and G30, respectively. This is feasible since there is only .050" difference in the narrower width of the Glock 10mm barrel chamber hood compared to the Glock 45ACP barrel hood. Of course, don't expect the barrel manufacturers to give the OK for use of their products in this application.

01-19-2013, 16:34
I'd think you need to have one barrel maker make a custom barrel. Such that its made to fit the 45 od and have it drill and chambered for 40 or .357 sig

Sort of a heavy barreled 40 or .357 sig, heck I bet you might even be able to flute it maybe

01-19-2013, 17:29
If a vendor wanted to make a "perfect" 45-40S&W conversion barrel for a G21 they could simply take the design of their G20 10mm-40S&W inhouse conversion barrel and make the barrel hood wider by 0.050" to better match the width of the breechface in the 45ACP slide. The barrel I.D. and chamber would already be correct for 40S&W, the barrel lugs are compatible, and the O.D. of G21 and G20 barrels are identical (

You should follow the exploits of GT member vaquero aleman from his post at He may be experimenting in the future with a G20 10mm-40S&W conversion barrel installed in his G21.

01-19-2013, 19:26
I just sent an email to storm lake to ask about 40 S&W and .357 sig conversions

01-20-2013, 18:09
i have a storm lake g30 10mm conversion barrel that works really well. I have heard people say they can shoot 40s in it but I wont do it since it head spaces on the mouth. why not just shoot 10mm since the factory stuff is close to 40 ballistics. 10 is more expensive but if you hand load the price will be the same. I doubt that the .050 would cause an issue but might effect accuracy some.

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01-21-2013, 10:58
I doubt that the .050 would cause an issue but might effect accuracy some.

It's surprising how little effect the .050" difference in barrel hood width has on accuracy. Below are shown the results of a test shoot (courtesy of GT member Desertscout) of a G30 45ACP pistol using the OEM G30 45ACP barrel on the left and with a OEM 10mm barrel taken from a G29 on the right. Nevertheless, you made the right choice going with a StormLake 45-10mm conversion barrel for the better chamber support it provides.

01-21-2013, 11:13
Nope. According to the Ptooma book, .45ACP can only be converted to 400 Corbon and 40 Super.

01-21-2013, 14:44
I don't see what would prevent it. You would have to use 10mm mags, but otherwise I don't see why the G21/30 couldn't have a .40 and 357 Sig conversion barrel made. They make them for the G20/29, so why not the G21/30?

01-21-2013, 18:14
Storm lake replied and said they were to busy at this point (back ordered) to take on new projects

But didn't say it wasn't possible

01-21-2013, 22:22
i am in the planning stages of a long slide for my G36 and woudl love both a 45acp and a 38s/9x23 barrel
while the extra slide weight of the long slide woudl put it close to the G29 i am not sure if the 36 frame woudl handle the 10mm or 9x25
ether way i want a 5 inch barrel witht the proper locking lugs and breach face for my G36

01-22-2013, 13:39
Maybe when things calm down some I can get something made

It seems anything that's 10mm parent should be able to be shot from G30/21's