Congrats on your .45-70, many here think it's the best of 'em all, including me!
I read an article by Gail McMillian (of McMillian barrel fame, yep that's him) and he said that for a quality barrel any 'break in' was a waste of time.
I bought my Handi in .45-70 ten years ago and it really looked un-fired. I didn't fire it until this year. I don't use hardly any jacketed bullets at all. I started with home cast and stayed there. With a scope, mine will give you inch and an eigth three shot groups at 100 yards.
I suppose I could break it in, but I'm not sure why.
Why don't you try yours out, it might surprise you. Either way, have fun. I sure do with mine.
Cat