Originally Posted by DocB
Hello Jeff, BB, and AZS,
For such a short thread there's been a ton of info here. I never cease to be impressed by the wealth of experience and knowledge in this group.
I am a padiwan when it comes to reloading and am always eager to learn from the Jedi Masters of reloading that we have here to guide us.
Questions I have are:
When you state "80 percent" are you referring to 80% of the neck length or neck thickness?
The partial neck sizing makes a lot of sense to me, albeit I am still a lowly padiwan. I use a Lee FL die and Neck Collet die and my 300WM is a 'factory' rifle.
How much of the neck is sized in this process and how would you go about setting up the die to size just a portion of the neck
When using a "washer", exactly what is it's purpose and where is it placed? I have seen 'shims' which are placed beneath the casing on the shell holder made by Innovative Technologies and specialized shell holders which are 'sized' to increase the shoulder bump. Is this also the purpose of the "washer" and how do you determine the thickness of the washer?
One last question: What is meant by "skim" trimming? I have an idea what is meant but I'm just not sure.
Ok, another question just popped into my head
: If you ream the necks in addition to neck trimming, would this process change?
I am very grateful and appreciative to you 'Masters' for sharing your wealth of knowledge and experience as well as your time and patience with us 'padiwans'
Skim turning 75 to 80% means you just take off as little as possible and if the missed sections on the case neck are only about 15 to20% of the total surface area then that's fine it is essentially straight now . As the case is fired more the neck may thicken a bit and another skim at the same old setting may clean them up more or even sometimes 100% .
However you have to turn all the way down onto the shoulder and just skim the very start of the shoulder just a fraction to make sure you have gone the entire length of the neck . If you stop short you can ceate a dough nut .
If you want to do partial neck sizing then you can not ever use a Full Length sizing die ever again . You have to separate the two sizing operations . 1 neck size die only and 2 Body die size .
The Lee collet neck die is quite ok for the neck size operation and works better with a skim turned case . The washer is placed over the case to be sized when it's in the shell holder so when the collet skirt comes down onto the washer instead off the shell holder the effective sized length is shortened by the thickness of the washer . The washer has nothing to do with the things you mention , they are part of sizing for shoulder bump and head clearance. Nothing to do with neck sizing length which the washer controls . I have never done it with a belted case so some adaption may be required as I don't know how much room is around the case belt diameter when on the shell holder but I can't see a problem .
This leaves the unsized section you want.
Then you have to purchase a Redding body die for the cartridge .
This is used when the cases start to get hard to chamber or at a certain number of firings that suits you .
A body die does not size or touch any of the neck of the case so your slight second shoulder set up by partial neck sizing is preserved.
If you can not buy a body die for your particular cartridge you can modify a Full Length die into a body die. By cutting the top off the die just a bit longer than the case mouth and drilling the neck diameter out to about .010 larger than the neck diameter of a fired case .
For a 300 WM the Redding body die you need is number 75153 .
Internal neck reaming can be done within this system ina factory chamber as there is no particular wall thickness required as there would be in turning for a specific diameter tight neck chamber . However skim turning and internal reaming is not such a good idea as it could leave the case neck too thin and increase neck to chamber wall gap even more which is what we are trying to regain with partial neck sizing and it's more prone to splitting .
A good option is skim turn the necks and polish the inside of the necks .
This can be done with an old worn bore brush wrapped in a small amount of fine steel wire wool and chuck it in a battery powered screw driver and run it back and forth inside the neck .
I hope that answers your questions.