Difference Between Taper, Roll, And Factory Crimps?

[charliez]

AFAIK:

- Roll crimp actually curves the brass inward towards the bullet.

- Taper crimp angles the brass inward

- But what is a Factory crimp?

I know folks favor the Lee Factory Crimp Die (FCD) why?

I have the Lee FCD too as that's what came when I got my die set.

[n2ipsc]

AFAIK:

- Roll crimp actually curves the brass inward towards the bullet.

- Taper crimp angles the brass inward

- But what is a Factory crimp?

I know folks favor the Lee Factory Crimp Die (FCD) why?

I have the Lee FCD too as that's what came when I got my die set.

The "factory crimp" die uses a collet to squeeze the case into the bullet/crimp it. Think of it as closing your fist tightly around something to constrict it, vs., say, driving something into a tapered hole.

The claimed benefits are insensitivity to trim length, and more uniform crimping. Personally, the greatest benefit I find is not needing to lube new brass for loading - conventional taper crimp dies (Dillon, et al) increase the reloading effort quite a bit and can "stick" enough to be annoying if the cases are not lubed.

I believe Lee offers the FCD in both persuasions - roll crimping for revolver cartridges, taper crimping for auto cartridges - I've no experience loading for round guns. The FCDs are all I use for loading for autos...

[kevin c]

I think that "factory crimp" is a phrase that only Lee uses to describe their FCD. I dont think anybody else uses that term.

If you search on the phrase "factory crimp die, you'll learn more about why many folks like to use it, though not everybody does.

[Skywalker]

Had to repost this, since in my original post the images were missing.

The difference between roll crimp and taper crimp is the following:

-Roll crimp bends the case mouth inward, thus creating a curve shoulder on the finished round.

Usually you would want to roll crimp bullets in their apposite crimping grooves. This kind of crimp is intended for revolver bullets and those semiauto bullets that headspace on the case rim, to prevent bullet travelling forth during recoil.

- Taper Crimp really "tapers" the case from bigger diameter (near bottom) to smaller one (near case mouth), leaving the sharp edge on the case mouth (unless you overcrimp, diving the whole case shoulder into the bullet).

This kind of crimp is intended for semiauto bullets that headspace on the case shoulder: it is higly recommended that these kind of bullets (i.e. bullets that headspace on the case shoulder) are taper crimped to allow round seating in chamber and contrasting the chamber shoulder, thus avoiding problems of round diving into chamber upon striker blow because they didn't stop onto the chamber shoulder.

(Images made to greatly exagerate crimping effect )

Factory crimp (term used by Lee) is nothing else than a crimping die with a sizing carbide ring added, to get rid of any bulging of the complete round due to bullet seating.

The carbide ring, on press lever downstroke, resizes the complete round ensuring it complies with "factory" specs for a loaded cartridge.

[charliez]

Thanks all!