Could a cut down 10mm to .40 come close to 10mm performance?

[crash813]

Taking out the discussion of needed spring weight, damage on frame, enough barrel support etc, etc.....
If you trimmed down a 10mm to the length of a .40, theoretically, you up the safe psi to 37.5k, aka .40 +p, would that approach get you close to 10mm performance? For arguments sake, say 180gr @ 1300fps? I'm wondering how much does the increase case size matter vs. velocity?

All theoretical here....don't go do this and blame me!

 

[tightgroup tiger]

I'm wondering how much does the increase case size matter vs. velocity?

Maybe not much, with all the different powders we have available today.

More powerful cartridges are usually made longer so they can't be chamber in the lighter made firearms.

With the right powder I feel sure you could get 10mm performance out of a 40 S&W case.
I'm basing this on getting 9 major performance out of 9 minor (Luger) brass, and it's done all the time.
.357 Mag performance out of 38Spl cases and so on.
That's doesn't mean we should do it. Those cases were made longer for a good reason and when we take away the air space inside of them by using shorter brass we are also cutting down the safety margin we have for a small mistakes with the powder measure. The shorter cases are much less forgiving.

 

[EricBu]

This is the same age old question "can I load my 38 spl up to 357 mag pressure?" Find and replace 38/357 with 41 spl/41 mag, 44 spl/44 mag, etc etc. Long as you only shoot that cut down case in a 10 mm, no prob. Mix it up and run it in a 40, you're going to be chasing your slide down range. Really though, most 10mm pistols won't cycle it, so unless you're shooting a revolver or tc or something, there's not much point to it.

 

[Mike L.]

Not everything that can be done should be done.

 

[N555]

40 already runs higher pressure than 10mm.

 

[GeoDudeFlorida]

Given the neck will also have to be cut back on the I.D., it seems like a lot of trouble to turn a $1 casing into a 9¢ casing. .40S&W cases are dirt cheap and plentiful; 10mmAuto isn't.
Wasn't there a question not long ago about how strong brass is compared to steel?
https://www.thehighroad.org/index.php?threads/is-the-strength-in-the-case-or-in-the-barrel.906120/

 

[WrongHanded]

40 already runs higher pressure than 10mm.

That's news to me.

 

[GeoDudeFlorida]

That's news to me to me.

SAAMI says no. 10mm Auto MAP is 37.5kpsi. 40S&W MAP is 35.0kpsi.

 

[WrongHanded]

SAAMI says no. 10mm Auto MAP is 37.5kpsi. 40S&W MAP is 35.0kpsi.

Ah good. So they didn't change anything whilst I was offline for an hour and 15 minutes. Perfect!

 

[crash813]

Given the neck will also have to be cut back on the I.D., it seems like a lot of trouble to turn a $1 casing into a 9¢ casing. .40S&W cases are dirt cheap and plentiful; 10mmAuto isn't.
Wasn't there a question not long ago about how strong brass is compared to steel?
https://www.thehighroad.org/index.php?threads/is-the-strength-in-the-case-or-in-the-barrel.906120/

Geo always hot on my trail to keep me honest! Wildcatters (with all 10 fingers attached) aren't created overnight. Gotta understand some of the basics that aren't always that obvious. Should of thought about the 38spl/357 mag but haven't seen anyone shoot one of those since those fancy talkie movies came out!

 

[crash813]

This is the same age old question "can I load my 38 spl up to 357 mag pressure?" .

My question, which I guess I should of been clearer with is how case volume affects 'power' (or specifically velocity) besides just controlling the amount of powder that can be filled in it. The easiest scenario I could come up with with .40 to 10 comparision. Maybe I should of asked, is there any reason they didn't make the 357mag the same length of the 38spl other than so people don't put the wrong bullet in the wrong gun.

 

[AJC1]

I would never attempt this in an auto pistol because the first problem is mechanical headspace and your messing with physical issues before pressure. In a 38 senerio the case headspaces on the rim so that issue is eliminated.... I run 20kpsi loads in 357 regularly in 38 cases. I don't own a 38...

 

[mcb]

Not necessary safe but with a good gun No need to cut 10mm down, just load the 40 S&W a little hotter. We are talking about ~7% overpressure its likely the gun saw proof pressures much higher than that. Again not particularly safe for shooter or gun but also not crazy. With light 10/40 bullet (ie 135, 155) you might get close to what 10mm can do with the right powder choice. As you move up in bullet weight the separation will grow even if you keep both peak pressures that same. The extra case volume of 10mm Auto is very beneficial when pushing the 180-220 gr bullets. You need larger volumes of slower powders to safely push the heavier bullet and stuffing a 220 gr bullet in a 40S&W does not leave much room for powder if your loading to SAAMI max length. I have loaded 200 and 220 bullet in 40S&w cases but in those cases I was loading longer than SAAMI for a double stack 1911 or a S&W 610 and I was not pushing the velocity. -rambling

 

[EricBu]

My question, which I guess I should of been clearer with is how case volume affects 'power' (or specifically velocity) besides just controlling the amount of powder that can be filled in it. The easiest scenario I could come up with with .40 to 10 comparision. Maybe I should of asked, is there any reason they didn't make the 357mag the same length of the 38spl other than so people don't put the wrong bullet in the wrong gun.

Pretty much yes, the 357 is longer so it won't fit into 38s. In the case of the 40, it was derived in the opposite direction. 10mm came first, Cooper developed the 10mm as a wildcat, back in the 70s or 80s....the 40 came afterwards because nobody (by nobody, mostly the FBI) was happy with the recoil of the 10mm, and reduced loads for it weren't working out (too much case volume). So the 40 came about in an attempt to make something that started with a "4" but didn't recoil like the 10mm, and the 40 was short enough that existing 9mm designs could use it with nothing but a different barrel and some minor redesigns, making it cheaper to get handguns into production.

 

[Walkalong]

All theoretical here.

Let's keep it that way.