If this is for a revolver, it depends on the length of your cylinder. My Ruger GP100 fits the pointy Hornady bullet just fine without trimming the case. Many revolvers with shorter cylinders, however, will need to have the brass trimmed in order to crimp in the cannelure. As for rifles, I can't comment because I'm not fortunate enough to own one in .357 mag.
Trimming the cases short will require a benchtop case trimmer. Nearly all the major reloading tool manufacturers make one. I own a Lyman. It works fine for what I need.
Kevin