Papa
I have a 45-70 Baikal which I'm fond of, I also have a what use to be a 30-06. I was not a fan of the 30-06 so I had 30-30 Winchester chamber adapters permanently installed without any problems. I did have to regulate the old fashion way instead of using the factory regulation but I prefer that. I'm sure you could use the monoblock as a basis and install 303 barrels without issue. Hope this helps

Very Respectfully
wcf 30