3 vs 4 die sets.

[Joker]

I am still new at reloading and so far I have a couple of sets of 3 die sets. I do see the difference is a "crimping die."

What exactly does this do, from what I understand it is more for the bottle necked rounds like many of the rifles and the .357 sig
so if that is the case is it necessary for rounds like 9mm and .40?

Thanks in advance.

 

[Tigerstripe]

still a 3 die set but i use a taper crimp die for my 45s. been using it a long time but i saw a difference when i started. it might be good for 40. 9mm cases are tapered. never had any problem with them.

 

[Regulis7]

I use the Lee Turret Press with the 4 hole turrets... De-Prime/Size Die, Powder Thru/Expander Die, Seating Die and Lee Factory Crimp Die for all my auto pistol loading and same setup with my .44 Special and .44 Mag. For full power mag loads I do switch to a roll crimp die instead of the LCF die.

 

[MGMorden]

Its different on bottlenecked cartridges vs straight-wall.

Bottleneck cartridges can technically get by with only 2 dies for many rifles - a FL sizer and a bullet seater. The flaring of the case mouth is done by the sizer die. Often a crimp die is included, but not always needed.

Straight-wall cartridges need a sizer, flare die, and a bullet seater (which also acts as a crimper). Lee also offers 4 die sets including an extra "Factory crimp die" for handgun rounds.

Personally, I've found absolutely no use for the 4th "Factory crimp die" on straight-walled pistol rounds. Once you get the hang of setting up your seating die its pointless to add another step. I do like having it for rifle rounds, but that basically means 3 die sets instead of 2.

So basically, for bottleneck cartridges (where the options are 2-die sets or 3-die sets), I prefer 3 die sets. For straight-walled (where the options are 3-die sets or 4-die sets), I still prefer 3-die sets.