I refuse to use a seating die for pistol or rifle that also serves to apply a taper crimp or roll crimp. I have two presses, a Dillon XL 650 and a Redding T7 which allows me a luxurious number of stations in the tool head for a separate crimp die. For any of my loading for semiautomatic pistols or rifles I apply a taper crimp that is appropriate for the projectile.
For example lightly jacketed, plated, or polymer coated pistol bullets get a very light crimp. Enough to remove case mouth belling from prior powder charging, and give just a smidge more tension at the case mouth. Before I start running a batch I pull the bullets to ensure just the slightest mark on the bullet and no jacket, lead, or polymer costing is being shaved off.
Bullets with heavier jackets and no cannelure get the same mild taper crimp, nothing to be gained going any heavier and just makes for increased effort of the press handle.
Any bullet with a cannelure I will adjust the crimp die to move the crimp into contact with the cannelure. Most duty ammo I’ve ever purchased where the bullet has a cannelure is made this way, both rifle and pistol and with few exceptions isn’t that much harder of a crimp, we’re talking less that 1/4 turn of the crimp die. That buys you a round that will put up with a lot more administrative loading and unloading, as well as just generally rough handling.
The only exception is for ammunition that is capable of generating serious recoil. Especially hard kicking revolvers. I load for .454 Casull, and full power loads with heavy for caliber bullets need a very heavy crimp. If you don’t do this there is a good chance you’ll end up with a tied up gun as your first couple of shots turn your revolver into a kinetic bullet puller. In my Speer manual there is a specific procedure outlined on how to use a taper crimp die to very slowly and very carefully push your brass fully into the cannelure of their Gold Dot Deep Curl bullet. I have yet to get any pull on these and as an added bonus the heavy crimp improved accuracy for me, probably made a more consistent ignition event for the 30.0gr of H110 since that powder doesn’t appreciate low pressure combustion chambers like a bullet moving too soon from the primer or very initial powder burn. I’ve read similar instructions for dangerous game rifles for the same reasons on combustion and bullet set back due to heavy rounds slamming into the front of the magazine under recoil as the rest of the gun comes back.
I’m not sure why everyone is arguing about this aspect, use some common sense and adjust your crimp according to your projectile and purpose. As an added bonus a separate crimp die makes doing that way easier. Also makes setting up your seating die way easier and more consistent.
