Read on a post about a 10mm Magnum round. Had not heard of it and wonder does anyone have the data on that round?

Starline sells brass. https://www.starlinebrass.com/10mm-mag-brass

Reloading Data can be somewhat difficult to locate. https://loaddata.com/Cartridge...Loading-Guide-2/4049

It doesn't appear that 10mm Magnum is officially recognized by SAAMI. https://saami.org/wp-content/u...roved-12-13-2022.pdf

That means research your loading data very carefully and know how to watch for pressure signs. There will be no official maximum pressure for a non-SAAMI recognized cartridge.

From what I've read about 10mm Magnum, the goal was to get closer to the .41 Magnum cartridge.

10mm Auto, and 10mm Magnum (rimless cartridges) headspace off the case mouth, and both of them require a taper crimp. Under recoil, the projectiles can "jump crimp" and come partly or completely out of the case mouth. This is generally a revolver problem/concern with the end result if crimp jump happens, is a tied up inoperative revolver.
If the projectiles move forward out of the case mouth in a semi automatic, they can/will jamb up inside the magazine.
I reload 10mm Auto (not 10mm Magnum) for both a semi automatic and a revolver, and have never experienced crimp jump.
My reloads are apparently not vigorous enough to have crimp jump occur.

I suppose there "might" be some obscure factory built semi automatic firearm chambered in 10mm Magnum, but it is unknown to me.

Most 10mm Magnum users are the folks that like to "tinker" and get their 10mm Auto revolver rechambered to the longer 10mm Magnum.

So if you are using/considering 10mm Magnum and have a serious usage for the cartridge such as self protection against large animals, the .41 Magnum, and .44 Magnum revolver cartridges which
are rimmed for headspace control, these have roll crimps, and are much less likely to experience crimp jump, and potentially locking up your revolver when you absolutely need it to function.

I'm no expert authority on reloading or cartridge design, but at least to me, 10mm Magnum was a "solution" that nobody needed or really wanted.

There are few semi automatic pistols chambered in .41 Magnum and .44 Magnum. Desert Eagle is one example.
Also, no 10mm Magnum semi automatics that I am aware of.
Most people wanting .41 Magnum and .44 Magnum power levels in a handgun are using revolvers. (or .480 Ruger, .454 Casull, .460 S&W, .500 S&W plus the Linebaugh cartridges, all in a revolver)
So why pick a rimless cartridge with a taper crimp (10mm Magnum) when .41 Magnum and .44 Magnum revolver choices, both for the gun and ammunition, crush the competition from 10mm Magnum.

If you just want a 10mm Magnum for the enjoyment of another cartridge choice, that's fine.
But if your life might depend on that 10mm Magnum revolver, .41 Magnum and .44 Magnum are better choices.

Not interested in having a 10mm Magnum just curious about it never having heard of it. Personally like 10mm as wood carry. If I wanted more I'd go 44magnum.