Would using a factory crimp die fix something like this or am I doing something wrong with the roll crimp die?
Says Mgregg
The FCD comes in a bottleneck rifle flavor and a straight walled pistol flavor. The mechanics of each is a little bit different. Further, the mechanics between roll crimped rounds and taper crimped rounds in the straight wall pistol category are worthy of mention.
With the bottlenecked FCD, there is a collet of sorts which is forced into a taper inside the FCD as you raise the ram. The collet closes four "petals" to press the case mouth of a properly trimmed brass case into the sides of the bullet. It does not affect neck tension at any other point on the case other than the very end of the case.
The straight wall pistol FCDs come in either taper or roll crimp. I had a roll crimp FCD for the 357 mag. cartridge that had a crimping ring that was designed for .357 inch bullets and would shave lead off my cast bullets. For a nominal fee, Lee sent me one for the .359" bullets I was loading then. This is a factor in the quality of the finished round.
The taper crimp straight walled pistol FCD doesn't impart a strong crimp, but rather returns the case mouth to near original dimensions to assist feeding, and perhaps it imparts somewhat of a crimp to the cartridge in the sense that it adds resistance to relocating the bullets. The taper type FCD like in the .40 Smith and Wesson has the tendency to resize the cases a little smaller than I would like when shooting lead bullets sized to .401 or .402" The results I think is that the carbide ring at the base of my FCD sizes the lead bullet to an extent that it becomes undersized for the bore diameter of my pistol. The brass casing "springs back" somewhat, leaving a sort of loose, resized, lead bullet inside the case. I get leading as a result. If I use a standard taper crimp dieby Dillon without the carbide sizing ring, I do not get the leading issue in my .40 cal.
Don't know if this explanation helps you any, but HTH>
Its a good set of starter dies and should serve you well for many years. The roll crimp die you refer to is actually a combo bullet seater and roll crimp die. The roll crimp can be "turned off" by installing the die a little higher in the press. Some people do this so they can use the FCD to crimp instead. This method will produce ammo that will almost always chamber in in most guns. This is a simple method to get good ammo quickly. Later on you can learn how to use the standard roll crimp die and make ammo that is just as good.
