YA, data stamp...
So can I shoot 7x57 Mauser out of my .275 Rigby?
Can I shoot .280 Remington in my 7mm Express?
And those are just off the top of my head (and the answers are "yes" to both)
And where would one find .30 PPC cartridges? Or even .222 Remington Magnum cartridges? Easy as pie to make, but it points-out the the "Data stamp" is just a guideline.
People are going to experiment, get over it.
I've "blown-up" a couple of guns, even the same one 3 times, it's not that big a deal.
Sometimes you should tie your gun to a bench and fire it with a string from behind cover... and sometimes you should just wear gloves and really good eye protection...
And people come here to find out which.
And to make your experiment work, first have a solid rod that fits down the full length of your barrel, then wrap the .223 case with tape, so that you need to slightly force the bolt closed, this will ensure good contact with the bolt face.
This will be one of those "fire it with a string" type events. Nothing on the gun will explode, but an awful lot of the combustion gasses will be coming back through the bolt raceway, it'll be acting like a ruptured case.
And you'll need the solid rod to knock the bullet out of the barrel because there probably won't be sufficent pressure to blow it out the muzzle. (some of the powder gas will escape up the barrel before the bullet seals the bore, the rest will escape out the back).
As always, post pix or video.
Or if you send me the gun, I'll do it. (I'd even supply the .223 round and remove the bullet if required).
Or if we used 222 RemMag, and I carefully wrap it in aluminum foil, that should prevent the case fom rupturing, and it's long enough to seal to the neck, it should work, and might even be repeatable.