I thought about just editing away the above "BTW", but the obvious answer as to why the bolt diameter was increased on 1882 and 1885 Remingtion Lees is that it was done to accomodate the .43 Spanish round which was VERY popular for Remington. There's likely more .43 Spanish R-Ls than 45-70. So....

It just came to me upon awaking for work today. Sure enough, the numbers work!