9mm-223AI?

Sorry for the title, but I was having a hard time thinking of something.
I was looking at a piece of my 223 ackley brass that I had on hand and noticed how similar the diameters are to the 9mm case. So I went to work with the dremel and cut the brass off at the shoulder. Then i resized it in my 357 mag die, followed by a 9mm die. I seated a 124 grain plated bullet using the regular seating die and the result looked fine to me, however I know that there are many more experienced people on here. My questions are...
1. Has anyone ever tried this before?
2. are there any major safety concerns with this?
I dont really have any grand plans to build a rifle in the near future, but i think something like this would be both fun and cheap to shoot. Thank you all so much for all of your help!

I have always wondered why this isn't more commonly done. I had never thought of the 223AI as being a candidate. I had always just assume that using standard 223 would work. Looking at the SAAMI specs, it seems regular 223 would NOT work. the Base of a 223 case is .3759-ish OD. While the bullet end of a 9mm case is .3800-ish OD. 223 brass tapers all the way down to .3542 at the shoulder. this is under the OD of a 9mm bullet. Using 223AI seems like a great idea.

Given a decent loading start point, I cant really think of anything that would make this unsafe. 357MAG data?

Again, this is something I have seriously mulled over, and I am curious about any shots fired from an actual build.

-PB

You wouldn't need to worry about the case head diameter difference between the 9mm and the 223. You'd be using a 223 bolt face which matches the rim diameter of the brass. A custom reamer from Dave Kiff and you're all set. It would be a fun plinker, but I don't think you'd find any bullets suitable for hunting. I'd run it out the extra .003 and make it a .358 based case where you would have a good selection of bullets out to 300+ grains. I haven't looked, but I'd bet it's already in Dave's list.

^ you would actually need to be concerned about case head diameter...in that expanding the bullet end of the brass far enough to fit a 9mm bullet in the 'neck' might actually give you a reverse taper...which is pretty much un-sat from a cartridge perspective.

In other words...the bullet end of the brass would be .3800 (if the brass is a similar thickness to 9mm brass).
While the case head area would only be .3759...which is smaller. Which would mean reverse taper. Now, its only 40-thousandths. which isn't THAT much.

After fire-forming, you would end up with straight wall cases. .3800 at the 'neck' and .3800 at the case head/base.

So kind of a .356/.357 Blackout?

IIRC what you have replicated (more or less) is the 9mm Super Cooper. Col. Jeff Cooper wrote an article about that concept in a 1911 frame for a trail gun back in the 80's I belive. He said it might be better than a .45 acp for outdoor use because of the flatter trajectory for long shots. I seem to remember that his vversion had a 6" barrel with a regular length slide. You might be able to find some info if you hunt around.

Quote:

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Originally Posted by macho mouse

IIRC what you have replicated (more or less) is the 9mm Super Cooper. Col. Jeff Cooper wrote an article about that concept in a 1911 frame for a trail gun back in the 80's I belive. He said it might be better than a .45 acp for outdoor use because of the flatter trajectory for long shots. I seem to remember that his vversion had a 6" barrel with a regular length slide. You might be able to find some info if you hunt around.

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As Spock would say, "fascinating".........

Thanks for all of the responses! And yes I was thinking something like a 357 blackout. Just thinking this would be easy to do in a bolt gun if it was possible, should also be cheap to shoot as well

Please keep us posted if you decide to act on your idea.