"Modern Reloading" does show some load RL-7 data for the 45-70, for 405 grain jacketed bullet. Min: 31.5 gr. Max: 34.5 gr. Max. CUP: 15800. From my own experience, I've found that a fast burning powder like Reloder 7 is better for a lighter bullet....say 300-350 grains. But, as the load data shows, it can also work with the 405's. As already suggested, IMR 3031 is a better choice. Varget also works well. A word of caution: If your goal is to turn your Baikal into a high velocity big game rifle, starting at max. pressure is not the way to go. First, you need to know what bullet weight, muzzle velocity and pressure the barrels were regulated for. There is some latitude with the Baikal, since its moveable wedge system does allow at least some limited barrel adjustment. But, within certain limits. Exceed those limits and either the barrels will shoot too far apart to regulate. Or, bullet impacts will cross. Again, likely too far to regulate. My advice, is to start with a load that duplicates factory muzzle velocity for the 405 grain bullet. Regulate the barrels to that load. I'd start at at 50 meters. Later, to 100 meters, if that is your ultimate goal. Then, work up slowly until you have a load that still groups well from both barrels, while leaving adequate barrel adjustment. If you have a chronograph, use it. This information will also be valuable in determining optimum muzzle velocity. Hence, downrange performance on game. It is very likely you're going to find that the rifle will still allow only a very limited range to work within. Double barrel rifles can be perplexing beasts to work with. Part of their allure, I suppose.
