Understanding the Lee Factory Crimp Die

18 August 2009, 19:21

I know there's been some discussion on this, but I don't understand the theory behind this die. Maybe someone can enlighten me. I'm a huge fan of Lee equipment, at least most of it, but what is the purpose of this type of crimp die, (the roll crimp die, not the taper crimper)?
I originally thought that is held the case in such a way as to crimp and not allow the case to be buckled. I understand a taper crimper, which can buckle a case under most circumstances. What is the sizing ring for? If it sizes a case down, then you would be ruining a bullets diameter, and thus accuracy, right? I mean, don't you have other problems, if a case it too fat to go in a gun? I just thought the idea was to allow a heavy crimp without a bulge at the crimp. I've read and had some experience where crimps don't matter, UNLESS, you're talking about keeping bullets in the cases from moving during recoil, other than that I dunno??
Can someone shed some light on this die and it's usefulness?
thanks guys.

18 August 2009, 19:28

craigster

It's designed, when set up properly, to duplicate the crimp that is used by the factories producing commercial ammo. Nothing more, nothing less.

18 August 2009, 22:24

homebrewer

The Lee Factory Crimp Die is used to crimp the casemouth into the cannelure on the bullet. It is to be used only on bullets that have a cannelure. To crimp a bullet that has no cannelure opens the possibility that the jacket might separate from the core. My gunsmith says this can lead to bulged barrels, so I don't do it...

19 August 2009, 00:24

SR4759

quote:
Originally posted by Bobby:
what is the purpose of this type of crimp die, (the roll crimp die, not the taper crimper)?
Can someone shed some light on this die and it's usefulness?
thanks guys.

Are you talking about the factory crimp for a handgun or for a rifle?

The rifle crimp die uses 4 collet fingers to apply the same degree of crimp regardless of case length.

Someone else can explain the handgun version. My understanding is it has a carbide ring in the bottom to iron out any oversize bulged out by the crimping operation.

19 August 2009, 02:44

tiggertate

Whoa! A lot has changed since I woke up this morning. The Factory Crimp Die never had a sizing ring to my knowledge. At least the 8-10 I own don't. Their sole purpose is to collet-crimp case mouths of sized, charged and seated reloads. They have a four-fingered collet that crimps the case mouth 90 degrees to the axis of the bore. There is absolutely nothing in the process that would buldge a case unless the die were grossly mal-adjusted. Has something changed recently?

19 August 2009, 03:51

TripletDad

From here: Lee Factory Crimp Dies

quote:
RIFLE

Lee Factory Crimp Die:

* Crimps the bullet in place more firmly than any other tool.
* It is impossible to buckle the case as with regular roll crimp dies.
* Trim length is not critical.
* Tests demonstrate that even bullets which have no cannelure will shoot more accurately if crimped in place with the Lee Factory Crimp Die.

PISTOL

Lee Carbide Factory Crimp Die

A carbide sizer sizes the cartridge while it is being crimped so every round will positvely chamber freely with factory like dependability. The adjustig screw quickly and easily sets the desired amount of crimp. It is impossible to buckle the case as with a conventional bullet seating die. Trim length is not critical so this extra operation takes less time than it would if cases were trimmed and chamfered. Revolver dies roll crimp with no limit as to the amount. A perfect taper crimp is applied to auto-loader rounds. The crimper cannot be misadjusted to make a case mouth too small to properly head-space. A firm crimp is essential for dependable and accurate ammunition. It eliminates the problems of poor ignition of slow burning magnum powders.

There is a difference between rifle and pistol factory crimp dies. You can use the rifle FCD to crimp non-cannelured bullets.

19 August 2009, 04:36

homebrewer

quote:
bulged barrels

versus

quote:
buldge a case

My gunsmith, a man of 45 years in that racket, told me never to crimp a bullet that does not have a cannelure. He was instructing me in the process of loading precision ammo for the gun he built for me. I asked him why. He said when you crimp a bullet that has no crimping groove, that brass has to go somewhere. It can separate from the core and will increase the diameter of the bullet. That brass gotta go somewhere...

When it comes to my guns, he's the expert and I adhere to his advice regarding those guns. He has built world-record shooters and has had six world records held with his guns at one time...

19 August 2009, 05:40

SR4759

quote:
That brass gotta go somewhere...

.375 Winchester (the 30-30 based round) came from the factory with an extremely heavy crimp. Some of those rounds tore the crimp off of the cases when fired.

This thread demonstrates that sometimes reloading and bullets casting should have separate forums for handgun shooters and rifle shooters.

19 August 2009, 21:44

larrys

homebrewer, just so you know, how do you think the cannelure gets there in the first place. In essence, they are roll crimped in, not cut. You can even buy the gizmo (technical term) that does it. For what it's worth, the brass goes INTO the bullet.

20 August 2009, 04:53

N. Garrett

The theory is that with the bullet held more firmly in place at the start of ignition, combustion is more efficient, with better accuracy.

I have several FC dies, and like them.

I've had several custom ones made, including for the 404 Jeffery and 458 RCBS Magnum.
I find them especially useful for hard recoiling cartridges where set back of the bullet might (and does) occur.

I remember maybe 20 years ago when I think it was Speer got in a pissing contest with Lee over the FC die. They put a notice on their bullets not to use it.

Lee countered with with ads that said the FC die worked well with all bullets except Speers.
Speer dropped the notice.

Garrett

20 August 2009, 06:02

SR4759

quote:
Originally posted by N. Garrett:
The theory is that with the bullet held more firmly in place at the start of ignition, combustion is more efficient, with better accuracy.

I have several FC dies, and like them.

I've had several custom ones made, including for the 404 Jeffery and 458 RCBS Magnum.
I find them especially useful for hard recoiling cartridges where set back of the bullet might (and does) occur.

I remember maybe 20 years ago when I think it was Speer got in a pissing contest with Lee over the FC die. They put a notice on their bullets not to use it.

Lee countered with with ads that said the FC die worked well with all bullets except Speers.
Speer dropped the notice.

Garrett

Speer and RCBS were owned by the same company then so there was a standoff between loading tool companies.
I never did figure out how you make a bullet more accurate by damaging it.
No bench rest shooters switched to FCDs to improve their groups.

20 August 2009, 08:07

BigJakeJ1s

The Lee CFCD is for straight wall, pistol cartridges, and uses a carbide post-sizing ring with a conventional type crimper. It will roll crimp rimmed revolver cartridges, and taper crimp rimless autoloader cartridges. IMHO, it works no better than a standard, separate crimp die, since if the post sizing ring is doing anything to your cartridge, its because a problem was caused elsewhere in the first place. Solve that problem first, and you won't need to iron over it with the CFCD.

The Lee FCD for rifle and bottleneck pistol cartridges uses a collet to apply the crimp, and works better than conventional crimp dies. The rifle FCD is of slightly different design than the bottleneck pistol FCD, but both work on the same collet principle. I actually wish they made a collet-style FCD for straight wall pistol cartridges too.

Andy

20 August 2009, 20:50

tnekkcc

quote:
Originally posted by TripletDad:

There is a difference between rifle and pistol factory crimp dies. You can use the rifle FCD to crimp non-cannelured bullets.

I like the Lee pistol FCD, but not the Lee rifle FCD.

With rifles, I shoot targets, rodents, and ruminants.

With handguns, I shoot chronographs.

21 August 2009, 04:10

Mort Canard

quote:
Originally posted by tnekkcc:

With handguns, I shoot chronographs.

Doesn't that get expensive?

21 August 2009, 07:23

tnekkcc

quote:
Originally posted by Mort Canard:
quote:
Originally posted by tnekkcc:

With handguns, I shoot chronographs.

Doesn't that get expensive?

I am trying to quit.
I have not shot a handgun or a chronograph in a year.
I am on my 4th chronograph.
It has measured many rifle shots.

22 August 2009, 04:18

N. S. Sherlock

BTW, there are several kinds of notably accurate match ammo around with heavily crimped cases and bullets and NO crimp canalures on the bullets. See the AR-15 ammo discussions for details.

I have some of that surplus 1952 Yugo 8mm heavy ball in brass cases and it is very accurate in my K-98. It is heavily crimped and has no canalures on the bullets either.

22 August 2009, 21:58

tnekkcc

quote:
Originally posted by N. S. Sherlock:
BTW, there are several kinds of notably accurate match ammo around with heavily crimped cases and bullets and NO crimp canalures on the bullets. See the AR-15 ammo discussions for details.

..

The NATO chamber so much free bore, that they try anything.