I just bought a H&R model 155 44 mag handi-rifle. Mine is one of the first generation. Mine, after spending 2 hours removing the leading, appears to have very shallow rifling. The twist rate is 1/2 revolution of the cleaning rod in the length of the barrel. Due to the amount of leading I am assuming the previous owner shot cast or the lead factory pistol loads. Any advise on this rifle with cast bullets will be greatly appreciated. I have shot cast for years, but this is my first 44 mag rifle.