30x223 vs 7.62x40 2ilson

[brstevns]

What is the difference between these two. Can a 7.62x40 be fired in the 30x223?

[rockrat]

30x223 is more like a 30x45. Its also a bit faster than the 7.62 x 40. The x 40 won't headspace in the 30/223 chamber correctly, but if you could get one to go off by seating a bullet out real far, you will move the shoulder forward on the x40 case and have very little neck.
Would be kind of like shooting the blackout round in the x40 chamber