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Modification of the Lee Factory Crimp Die
MikeG on 2013-08-01

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Modification of the Lee Factory Crimp Die








 The Lee Factory Crimp Die is an essential part of the cast bullet shooter’s set of tools.  For those not familiar with the product, it provides a stab-type crimp at the case mouth which is not affected by the exact length of the case.  This is pretty vital for the reloader who likes to tinker with cast bullets in rifle cartridges for several reasons.  Cast bullet loads in rifles, unlike jacketed bullets, almost universally benefit from the bullet being seated to touch the rifling.  While reloading manuals warn this is a no-no for jacketed bullets due to the increase in pressures, it is a pretty vital step with cast bullets.  Cast bullets have much less resistance to engraving the rifling and the little bit of extra resistance, plus the fact that the bore will be sealed sooner, aid proper combustion of the powder and help prevent powder gasses from eroding the sides of the bullet.  And, while crimping is not required for single shot rifles nor for single-loading repeaters, crimping is absolutely required in rifles with tube magazines to prevent bullets from being forced deeper into the case under recoil.  Since not every rifle throat is identical, the cast bullet selected by the reloader may not end up with a crimping groove in the right location.  This is not a problem with the FCD and cast bullets – it will form a crimp groove whether there is one or not!


 Oddly  enough, for all the advantages for rifle shooters, Lee has not generally made this product available for straight-walled handgun cartridges.  Instead, a completely different product with a confusingly similar name is offered, the Lee Carbide Factory Crimp Die.  Note the word “carbide.”  Like the carbide sizing ring in a resizing die, that product will squeeze down the entire external dimensions of a loaded round.  While this may work for some applications, it tends to cause problems if bullets are not exactly at nominal dimensions.  Since cast bullets often work much better at anywhere from 0.001” to 0.003” over nominal bullet diameters, this product can cause more problems than it solves for the cast bullet shooter.  As an example, in the .44 Magnum it is common for knowledgeable shooters to use bullets up to 0.432” instead of the more standard 0.429” if required for the particular gun.  Squeezing down the bullet to smaller dimensions than the groove diameter of the firearm is a recipe for trouble with cast bullets, guaranteed.


 To their credit, Lee does offer custom services (although those are currently suspended as of this writing).  Still, there must be a simple solution?  Perusing the Lee web site, it was noted that there is a Factory Crimp Die with the stab-type crimp offered for bottlenecked handgun cartridges, including the .44-40.  So, with the case length and bullet dimensions being nearly identical as the .44 magnum, would one of these dies work for a .44 mag?  And if so, would it be adaptable to similar sized cartridges, such as the .44 Special and .45 Colt?  There was but one way to find out and several of the dies in .44-40 were ordered.


Backing up a little, the first Lee collet dieI owned was for the .300 Weatherby.  I did not own a .300 WBY at the time, nor have I ever, but it was picked up used, for next to nothing, out of curiosity.  Taking the die apart revealed that the collet on the inside was held captive in the die by a short length of wire that caught a ledge in the bottom of the die body.  Studying the die led to the belief that the die would work for any other shorter .30 cartridge if the collet and die body were simply shortened.  This was tried and presto, my .300 WBY die was shortened enough to work perfectly in the .30-06, a cartridge I could use it with. Success!  The only caveats were that the collet would have to have enough material remaining below the slots to hold the pieces together, and if the die body was shortened enough to remove the ledge that caught the retaining ring, the collet would fall out instead of staying up in the die.


The second Lee FCD that I modified was for a .458 Win Mag.  At the time I needed a crimp die for a new cartridge, the .500 JRH, and the .458 die was again surplus to my current needs.  Since the location of the collet shoulder in the die body could not be easily changed, the die body was cut down to fit the much shorter (1.4”) JRH case.  This left the die so short it could not be screwed far enough into the press!  The knurled ring  at the top of the die was then turned off and the die was now screwed in from the bottom of the press.  Quite acceptable for experimental/prototype purposes, but hardly elegant.


That part of the die modification was simple, but it still needed a collet.  Having no idea what types of steel might be appropriate, the scrap pile was perused.  An old, rusty bolt that had been found in the street was about all the raw material that was on hand of the proper diameter.  Well….. since it was an experiment, why not?  A collet was turned out in what was hoped to be the correct dimensions and angles.  The slots were cut with a small bandsaw (and not very straight) and deburred.  While the end result was as ugly as a mud fence…… it worked!  Upon closer inspection, the collet slits on the .458 die weren’t perfectly straight either, so I didn’t feel quite so bad about my effort.


Various collets








Back to the .44-40 die.  The first thing that was attempted when the dies showed up was disassembly.  While the rifle dies came apart easily, the handgun dies were a different story.  No amount of prying, banging, pressing, or strong language was enough.  I even tried using the bench vise with a bolt through the top of the die to press the collet out.  No luck.  Hmmm.  Examining the die body suggested maybe the bottom of it was crimped, so it was chucked in the lathe and a little bit turned off.  The earlier sequence was repeated (pry/hammer/press/curse), but with no progress made toward the goal.  Finally it became obvious there was a different locking mechanism and any more machining of the die body was going to leave it too short to be useful!


At that point, I wished for a hydraulic press and decided to push the collet out by whatever means necessary.  Finally the light came on and I realized that a very strong mechanical press was right in front of me, with the letters RCBS cast into the side!  Reloading presses have a LOT of leverage at the top of the stroke.  The die was screwed into the press from the bottom till the knurled ring cleared the shellholder.  A short piece of steel about half an inch in diameter was turned square on both ends and about an inch and a half long.  A shellholder large enough for the rod (for a .45-70 to be exact) was installed.  The press handle went down, the ram went up, and with no more pressure on the handle than resizing a case, the collet popped out the top of the die!  Why it didn’t work in the bench vise was a mystery until it occurred to me that the bolt I was using was slightly tapered on the end and was probably forcing the collet fingers out against the retaining ring in the body of the die.  Yes, I am slow sometimes…


Removing collets


 After trying the die on a loaded .44 mag cartridge, it appeared to be a bit short.  Remembering the lesson of the .300 WBY die, the collet was machined off about 0.025” and now worked perfectly!  The die body that had been shortened would serve for the .44 special, and another collet was shortened enough to serve for that cartridge.  The short die body did serve the purpose of making it obvious which die was for which .44 cal cartridge, a small upside to the earlier mishaps.


Would the die work for a .45 Colt?  More modifications were needed.  Specifically, the collet would have to be enlarged on the inside.  Machining the collet after the slits had been cut would be problematic.  A tip in a machinist’s magazine suggested putting gel-type “super” glue in the collet slits and letting it set up before machining would prevent vibration and chattering, which worked perfectly.  The glue could be dissolved with acetone after the collet was modified.  This was tried and worked perfectly.  The crimp part of the die was bored out just enough to clear the neck of a loaded cartridge, and the body of the die was then bored out for additional clearance.  Again, the collet had to be shortened about 0.025” for the .45 Colt.  The results were outstanding.

Modified collets and die body 


Unmodified die body, .44 Special die body, unmodified collet, .44 mag collet, .44 special collet with die body showing retaining ring and collet shoulder, .45 Colt collet.


For the reloader with a lathe or access to one, these simple modifications can be made to enlarge and/or shorten the collets on the .44-40 factory crimp die for use with the .44 mag, .44 special, .45 colt, et  al.  Collets for other similar cartridges which are either longer than the .44 mag (ie. .500 JRH) or smaller in diameter (ie. 357 mag) can be fabricated easily. It is unfortunate that Lee does not offer these as a standard item for handgun cartridges that are commonly used with cast bullets.  While these modified dies may not solve every reloading problem, they are a very useful tool for the cast bullet shooter.



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