500Nitro, I dont think it needed clearing up, the original poster asked about Light 577 , which most people take as Nitro for Black loads, this can be in (or shorter) 2 3/4in , 3in or 3 1/4in as there were Black powder rifles in these lengths & most had a LN load for them, the 3 1/4in being in a heavy rifle can be very powerful , close to 2 3/4in Nitro loads !

The rifle to make, for me is a LN 577 in 3in (saves on the case work) & using light 577NE 2 3/4in loads, this can be made on a 12ga action, there is a big difference between 12Ga actions how ever as some are as big/heavy as a 10ga !

I just missed another Top lever hammerless 577BPE 3in, so I'm going to get one made now bugger it !

Unless you can get me old Stumpy from up North ?