Lee Collet Die with Donuts - Problem solved

[ratbuster]

I get donuts in my 20 Vartarg Lapua cases. They disappear upon firing but recur upon body sizing. Donut size varies depending on # of firings and the individual case but with enough firings the donut becomes too large for the mandrel of the collet die to pass through so my options have been either reaming the donuts or using a bushing die.

I prefer the LCD over the bushing die. It produces less neck runout and in multiple tests on target the LCD makes ammo that shoots tighter groups than ammo done with a bushing die.

I don't like reaming donuts because the reamer can leave an inconsistent surface scratches inside the neck and I think reaming may shorten brass life so I have resorted to the bushing die.

I tried something the other day that worked out as hoped: I simply shortened the mandrel so the end of it sits just above the donut. Since the bullet base is well above the donut I am getting 100% neck sizing for the bullet. It works perfect.

 

[243winxb]

From Lee-
Partial neck sizing with collet die
Posted by on 13 August 2015 03:19 PM
If you want to resize just a part of the neck, find a washer at your local hardware store the has an inner diameter large enough to fit over the case, and an outer diameter large enough so that it contacts the collet sleeve that protrudes from the bottom of the die. Slide this washer over the case after the case has been inserted into the shell plate. Now when the ram is raised, you can still close the collet by applying force at the top of the stroke, but the case will not go up as far into the collet, and the neck will be sized less an amount equal to the thickness of the washer.
http://leeprecision.net/support/index.php?/Knowledgebase/List/Index/13/product-support

 

[ratbuster]

From Lee-
Partial neck sizing with collet die
Posted by on 13 August 2015 03:19 PM
If you want to resize just a part of the neck, find a washer at your local hardware store the has an inner diameter large enough to fit over the case, and an outer diameter large enough so that it contacts the collet sleeve that protrudes from the bottom of the die. Slide this washer over the case after the case has been inserted into the shell plate. Now when the ram is raised, you can still close the collet by applying force at the top of the stroke, but the case will not go up as far into the collet, and the neck will be sized less an amount equal to the thickness of the washer.
http://leeprecision.net/support/index.php?/Knowledgebase/List/Index/13/product-support

That would not work for a donut problem. The mandrel as provided is way too long. It has to be shortened.

 

[T-shooter]

An expanding mandrel will work. You can get them in about any size. The screw in this one is to limit the depth so you don't ram the neck into the base.

http://kmshooting.com/case-neck-expanding/expand-mandrels-656/expand-mandrels.html

 

[Dusty Stevens]

Another neck sizing issue post?

 

[JohnKielly]

I believe that reason that the Lee die produces such straight brass is that the mandrel is aligned thru the case flash hole and therefor if you shorten the mandrel, you risk case neck runout.

Faced with the same circumstance, I would reduce the diameter of the mandrel below where you want the collet to act on the neck. I've found that I can see where the collet bears on the mandrel after some use, making it a relatively easy job to reduce the mandrel diameter below that point.

 

[ratbuster]

Another neck sizing issue post?

Dusty,

This post is not really about neck sizing. It's about using a Lee Collet die when donuts are present. I know you have stated more than once that you don't like Lee dies but the LCD is an incredible tool. Case neck run-out ranges from zero to only a few tenths with no lube. You can't get that kind of true with a bushing die. Sorry but you can't! Of course a body die is used in the process so the case gets proper sizing throughout.

 

[ratbuster]

I believe that reason that the Lee die produces such straight brass is that the mandrel is aligned thru the case flash hole and therefor if you shorten the mandrel, you risk case neck runout.

Faced with the same circumstance, I would reduce the diameter of the mandrel below where you want the collet to act on the neck. I've found that I can see where the collet bears on the mandrel after some use, making it a relatively easy job to reduce the mandrel diameter below that point.

I could see why you think the mandrel becomes aligned with the flash hole therefore contributing to straightness but that is not what's happening. If the LCD depended on the flash hole for alignment then any brass with off center flash holes would be a problem. Also it would require a precision fit between flash hole and decapper pin which is not always the case.

I have always removed the decapper pins from my collet die mandrels because I prefer to deprime by hand and runout has always been zero to super low. Of course I checked run-out after shortening the mandrel; there was no change at all.

Your suggestion to reduce the diameter below the top of the donut is a good one for those that want to retain the decapping pin.

 

[ratbuster]

An expanding mandrel will work. You can get them in about any size. The screw in this one is to limit the depth so you don't ram the neck into the base.

http://kmshooting.com/case-neck-expanding/expand-mandrels-656/expand-mandrels.html
View attachment 1058676

I have used an expanding mandrel to deal with donuts but with my some of my vartarg cases the donuts have so much resistance to expansion the shoulder collapses. After a few of those you quickly try something else.

 

[Richard Coody]

well other than ignore them and partial neck size seating the bullet above the donut the most common way of dealing with donuts is simply move them to the outside with a mandrel or even a full length die with expander ball and turn them off with a neck turning tool. as thicker shoulder brass migrates into the neck the neck gets thicker. turning necks and making that cut into the shoulder reduces the tendency for donuts to form. partial neck sizing increases the likelihood of donuts forming.