quote:

10mm is registered at 37500 psi
40sw is registered at 35000 psi
---------------------------------
7.1% difference, advantage 10mm


10mm is registered at 1.260" OAL
40sw is registered at 1.135" OAL
------------------------------
11% difference, advantage 10mm

Given those constraints with a 4.6" barrel, we would expect at best

200 gr. XTP JHP
10mm 5.8 gr. Bullseye 1089 fps = 218 PF
40sw 4.3 gr. Bullseye 969 fps = 194 PF
------------------------------------------
12 % difference, advantage 10mm

135 gr. Sierra JHP
10 mm 9.3 gr. Bullseye 1496 fps = 194 PF
40sw 7.8 gr. Bullseye 1411 fps = 190 PF
-----------------------------------------
2% difference. advantage 10mm

With poor case support barrels and / or factory loads and / or published handloads that may be the end of the story.
But with custom handloads and custom barrels that do not leave the thin case wall of the cartridge case unsupported, then strength from the cartridge design comes into play.


The LARGE primer pocket on a 10mm is .2100" inside diameter.
The SMALL primer pocket of a 40sw is .1745" inside diameter.

The extractor groove of .335" makes the brass case wall .0625" thick in the 10mm
The extractor groove of .335" makes the brass case wall .08025" thick in the 40sw
----------------------------------------
28.4% difference, advantage 40sw

Extrapolating from the thickness, if the 10mm can do 37500 psi, then the 40 should be able to do 48000 psi. But in reality, the pressure required for primer pocket failure of these cartridges is much higher. A Glock 22 40sw with custom barrel and custom handloads can be much more powerful than the best that can be done with a Glock 20 with custom barrel and custom handloads. The difference is much more than 28%. This can be roughly explained with hoop stress:

[Max Chamber pressure] = (Max hoop stress in brass around primer pocket) [2 [OD - ID]]/ [ID]


H06 tempered C26000 cartridge brass max stress = 65,300 psi (initiation of yielding)

Max chamber pressure 10mm = [65,300 psi] [2[.335" - .21"]]/[.21"] = 77,738 psi

Max chamber pressure 40SW = [65,300 psi] [2[.335" - .1745"]]/[.1745"] = 120,122 psi
--------------------------------------
difference 55% advantage 40sw


The max chamber pressures are, in reality, less than that, because the stress on the brass is not only tangential to the primer pocket, but there is also an axial compression. Those stresses can be combined and calculated and gives answers that track experiments, but requires Von Misses calculations that are way hard.

quote:

Originally posted by rebel102285:
No i couldnt just trim a 10mm case down in order to comply with state law it must be .992 or larger

quote:

Originally posted by tnekkcc:

quote:

Originally posted by rebel102285:
No i couldnt just trim a 10mm case down in order to comply with state law it must be .992 or larger

Put a 27/64" drill in a chuck and twist it in hand until the 10mm case will chamber.
Put a "Y" drill in a chuck and twist by hand until a dummy 10mm cartridge will chamber.

You will have irreveribly converted that barrel to 10mm.

I have done something similar for converting 9x19mm barrels to 9x23mm, and it works better than the Clymer 9x23mm reamer.

If you want hot loads in a 10mm, put 30-30 brass in a lathe and turn it down until it fits. Make the extractor groove shallow.

quote:

Originally posted by muck:
DO NOT under any circumatances put a drill bit into a barrel to"rechamber".

AGAIN UNDER NO CIRCUMSTANCES PUT A DRILL INTO A BARREL INORDER TO RECHAMBER.

To start a chamber reamer is a very precisly machined tool with a very specific shape/design.

Your rimmless cartridge headspaces on the step machined into the barrel by the reamer.
A drill bit has a slopped edge, there for no step/ledge to stop the cartridge from moving further into the barrel(headspace again).
Using a drill bit will at best leave you with an unreliable firearm, at worst a very dangerous gun.

muck

quote:

The internet has 5 Chicken Littles for every guy who knows what he is doing.

quote:

Originally posted by tnekkcc:
I have chambered rifles, handguns, and shotguns with boring bars, drills, staight fluted .001" increment reamers, adjustable straight fluted reamers, solid pilot reamers, floating pilot reamers, separate throating reamers, emery cloth, mill bits, Scotch Brite pads, steel wool, Dremel Carbide bits, files, valve grinding compound, and combinations of these.

They all work, if you know what you are doing.

The internet has 5 Chicken Littles for every guy who knows what he is doing.

quote:

You could trim a 10mm case from .982" to .840" and use a 10mm case in a 40 S&W chamber.

quote:

Originally posted by Mark:


One wonders how we all survived back in the "old days"!

If you use your brain and really think things out, you can do a suprising amount of stuff with quite few physical resources.

Additionally, if you choose not to use your brain, all of the high-dollar gizmos in the world may not give you good results.

quote:

Originally posted by jeffeosso:
40's will fit in a 10 (most of the time) and work, 10's are too long.


what state do you live in that wants a long case?

jeffe