sgtt,
1. If "case forming" is firing a standard cartridge in an improved chamber to give it the shape and powder capacity of the improved chamber, then firing a bulleted round is the easiest and safest way to do this.
2. If "case forming" means firing a a correct diameter case in a chamber with a longer shoulder to make reloadable brass, then, yes, it's still easy, if it is a rimmed case. Use a light charge of shotgun powder (Red Dot, Green Dot, Blue dot and fill the case with Cream of Wheat cereal topped with a bit of tissue paper. Starting charge should be about 6 yo 10 grains, depending on case size. I've used 10 grains Red Dot in .30-30 to make .38-55 this way.
3. Case forming bottlenecked cases is trickier, and is best done with bulleted cartridges.
HTH
John
