M91 “Calvary” Carbine for my son

[Ovidio]

I didn't slug the bore on this one, because there is no reason. It is 100% as issued, plus it was treated really well.
The diameter should be .268 between grooves, not lands. The military bullets have the same diameter, and weigh 162 grs. (about. I weighed a few and there are a couple grains tolerance, I have the feeling).
.264 can be found, but in that case, these are rebarreled rifles. There is a company here in Italy, which has rebarreled quite a few. There is right now a guy selling one of those .264 Carcanos (a 41) close to me, here in the North-East.
They have no particular markings, so these rifles can be dangerous, because if you shoot .268 through them, the pressure skyrockets.
I don't know of any such rifles having been exported, but I'm far from being an expert on this. But considering that those jobs were made the earliest in the mid- to late eighties, if not even in the nineties, I don't think there is much of a chance that any of those reached the shores of the USA.
The original Carcanos have a 4-groove barrel, with right-hand rifling. These others, if I'm not wrong, have a 6 groove barrel.
If you want a lot of info, try visit this site: www.il91.it. Everything in Italian, but with the translators you can now have a much easier access to the contents here.
In case of doubts, pop me a PM.