Differences bettween 760XL and 761XL?

I had one of these when i was a kid, of course! I would put this around 1979-80. I would like to pick up one for my 8 year old son. My thing is this i want a all metal and wood model with a rifled barrel "for best accuracy".

Can i get a explanation of the differences between the two models in the title above.
Would also like to know what the differences were between the standard 760/761 and the 760XL,761XL