45-70
I've recently aquired a 14" barrel with muzzle break on a Contender frame. I like it, however I am still learning about it.
I've shot it about 50 times thus far; a box of Winchester 300 grain SJHP, and the rest an assortment of reloads using RE7 (loads of 46.0, 47.0 and 48.0 grains), Winchester brass/large rifle primer, and Remington 300 grain SJHP bullets. Of the three loads, the 47.0 grain is grouping the best, about 2" at 30 yards (offhand-supported over the hood of my truck). Results are less than desirable; more fine tuning is in order. The force of the recoil is mostly to the rear, on account of the muzzle break, and is felt even the day after shooting 30 test rounds of reloaded ammunition. It was fun at the time though.
I doubt that I will load 48.0 grains of RE7 again, as I believe I observed signs of high pressure-black gas marks on breech (a little help here from experienced reloaders/shooters would be appreciated).