Thanks for the replies guys! So its safe to use 3FG in the .45-70 but it may not be the best choice for accuracy - guess I have to do some extensive testing!
But really bad accuracy would surprise me, all my guns love 3FG and shoot great with it.
By the way, whats the purpose of a wad between powder and bullet? To protect the base and act kind of like a gas-check? Is this really necessary with ordinary low pressure blackpowder?
I don't use any wads in my muzzlelaoders, I tried but they don't react well to any kind of lubed wadding behind the bullet, accuracy usually goes to hell.