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