Congratulations and good shooting with the Rossi! - Had the choice between Rossi and Winchester when I was shopping for a 45 lever action: They really compared very well and I got the Win just about 'tossing a coin'
On the semi wad cutter bullet - I use the Lyman 452424 which casts a 255 gn with a very broad flat nose, the weight seems about right for the rifle and though a little heavy for the revolvers it seems ok in my Ruger Vaquero (the Lyman Handbook recommends for Vaquero and Contender only) - since my other 45 is an Uberti I guess it complicates logistics a bit. I don't have an RCBS manual handy but I take it that your mould casts 250 gn - not much difference.
Would a primer fire from a nose slightly
smaller? - hardly a 'firing pin' but i guess the risk is there - as it would be, on the other hand, from a litle convexity in the broader nose... someone out there got any suggestions?
El Chimango Pete (aka Peter Knight)
'A 44 beats 4 aces'