Well I guess everyone is entitled to their opinion but I have been using the Lee factory crimp dies in my .270, 06, .223, and 300WM. IMO it does improve accuracy. I shot several groups withthe same load crimped and uncrimped and did notice an accuracy difference. And to be fair, I cleaned the bore after each group to ensure fouling would not be a variable. As for revolver and other straight walled cases (like the .45-70) I roll crimp the bullet in place. The only ammo I don't crimp are the auto pistol (.40 S&W, .380, .45 ACP)