I am getting ready to start reloading for 40 S&W. The gun is a Smith and Wesson M&P 40 S&W. From what I have read it is advised not to roll crimp these rounds but instead use a taper crimp. Is the taper vs the roll crimp a function of the type of Die I purchase or the method used? In other words, are there taper crimp dies and roll crimp dies? Most of the die sets I see come with 3 dies but many suggest the bullet seating and crimping stage be done separately. Do I need to buy a 3-die set and then purchase an additional taper crimp die?

PS - I am using a single stage press, if that matters...

The seating die generally has the crimp on it, but not always. Some seating dies don't crimp at all, if your die does not crimp you'll need a crimp die also. For any semiauto that seats on the neck you need a taper crimp. Revolvers/rimmed cartridges get a roll crimp. Most rifle rounds are also taper crimped.

Which dies do you have?

Sam, Thanks for the response. I have not yet purchased a die set. All my other dies are RCBS and that is probably what I'll buy. I realized that I need to taper crimp, the question is, is this a specialty die to purchase or what a 3-die set already comes with? Also, it seems like many people prefer to seat and crimp with separate dies...not sure how you feel about this?

From looking at the die instructions the RCBS dies will taper crimp while seating. I crimp in a separate step on a Lee Loadmaster progressive press using the Lee Factory Crimp Die. On a single stage I'd try a few first to save the extra step. If I remember right on the RCBS dies you can adjust them to not crimp, or how much crimp there you want. It's been a while since I used the RCBS dies but that's what I started with too. My first press was a Rock Chucker making .45 ACP.

I think the arguement against crimping and seating at the same time is that you are pushing the mouth closed while it slides up the bullet. The bullet stops against the seating die and the shell is still moving up scraping the side of the bullet. Personally I think if your not over crimping it shouldn't make much of a difference to do both at once.

Most all autos (including the 40S&W) head space on the case mouth, this means that they must be taper crimped or uncrimped. To do otherwise would cause a dangerous head space problem. Die manufactures know this and customarily make dies accordingly. Roll crimps are generally used on revolvers with heavy recoil and rifle rounds, because they head space on the rim or case shoulder.