Ravin, I have exactly what you're talking about. Handled an estate for a friend several years ago that included a completely disassembled L46. We scratched around and found enuf parts to reassemble the thing with a few mods, but then discovered it had been rechambered to .223 Rem without remarking the bbl.
Didn't bother me, because I was set up for both calibers and the rifle was in too rough a shape to be very valuable. But, it turned out to be as accurate as any rifle I own. Half inch groups are fairly common and I'm no benchrest shooter.
However, 55 gr bullets are the heaviest I've been able to get to group. Hornady 60 gr bullets aren't accurate, 45 gr TSXs shoot great but 53 gr TSXs don't, and, just for the heck of it, I tried Speer 70 gr and they were awful.
I would never rechamber a fine example of this beauty. Value would suffer and you would not realize much gain in performance. If I liked this rifle enough, I'd scrounge up 222 ammo and use it. If I wanted to shoot a lot, I'd sell this L46 and buy a 223. I suspect you'd end up with enough extra cash to buy a load of ammo. But that is my opinion. The rifle is yours and you need to do what you are led to do with it.
