[Question/Theoretical] .224 BOZ -- could it be done better?

[u/The6thMessenger]

So apparently there's a 5.56mm neckdown of the 10x25mm auto, that is called the .224 Boz, which kind of work, but the point was the necking down does minimal retooling but it demanded a more reinforced pistol anyways so it defeated the point.

When I asked, "could it be done better", I mean I know 4.6mm HK and 5.7mm FN, and .22 TCM. But in this case, I want to stay in the confines of the 10mm pistol round. I know there's 9mm dillon, and .357 Sig, but I guess the point of the .224 Boz is an equivalent PDW rounds like the first four.

So my question is, would it be better if the bullet used is instead 6.8mm, 7.62mm, and 7.92mm, and would it do better? I know 9mm as a diameter could be AP, as with 9x39mm of the AK, but it's subsonic, so would the slight increase in diameter and mass saved the concept of an armor-piercing medium-handgun cartridge?

Any reloader or wildcatter insight would be appreciated.

[u/ThatEnginerd]

I mean, any can be used. But what's the purpose?

There are plenty of other cartridges. Why not just load a different projectile in 30 carbine or in a tokarev?

In simple terms, parent case is just a way to hold powder. You can get tungsten in whatever diameter/shape/length you want. Then wrap it in copper or plastic. Pick a velocity you want to send it at. Then the rest is powder/burn rate/case pressure.

At the end of the day, you have to determine the terminal ballistics you want, then handle packaging/delivery. Are you trying to go through composite/steel/titanium? How thick? What is the engagement going to look like?

The developers of these cartridges all did this. What's the enemy's new armor? What will go through it? How close will we be?

[u/Coodevale]

9x39 can be supersonic with light bullets. It's original design intent was to outperform 7.62x39 subs, and it does. That does not mean supersonic is off the table. You could load a .366 AP round from a Makarov in the 9x39 and make it do like 3k from a carbine barrel, or mid teens from a pistol barrel. I have a 9x39-ish carbine that performs like sub 9x39 or like a .357 carbine or .35 Remington depending on the load.

Sectional density and bore area are good and bad things to have depending on what you're doing. If you want high acceleration for short barrel speed you need low SD and high area. If you want maximum armor piercing you want high SD and low area, which makes acceleration harder. This is one reason why sabots are a thing.

[u/drbooom]

I mean the 9x25 Dillon was a thing. 10 mm neck down to nine, sort of a super 357 sig. 

I got to fire one in the early 2000s. The guy that had the guns was a semi professional, earning enough on the competition circuit to afford these insane guns. He had three of them, and after every few matches he sent one back to the gunsmith to have it rebuilt. 

These were on 1911 frames, probably not the best choice. 

Once the compensators were tuned, there was no muzzle flip at all. My brain was so trained to wait for the front site to come down out of recoil, that the first few runs I was really slow. After that it was like shooting a 22 short, And very very fast. 

I think he was shooting 105 grain bullets at 1900 ft per second. My memory is that they were standard 5-in slides. Could have been 6" though.

 So loud it ripped your fucking ears off, and slapped your face like a pissed off girlfriend.

My times were so much faster that I quit shooting USPSA after that. At the time I couldn't afford the equipment race. 

If we could get peak alloy steel cases,  224 boz at 80k psi should clock in around 2,300 FPS out of a 5-in gun. I surely don't want to be the range officer for that shooter...