Shell holder making for Headspace for the impaitent
This is what I did for my SAUM so I didn't have to order in a shell holder to suit…. :)
Now I have gear to measure the shoulder to tell when I am bumping a fired case to find my headspace but plenty don’t so I though t I would scratch something up without using it to much (well yes I was using it to double check) and in this description I mod a shell holder for a rifle that the Redding competition set I had didn’t cover what I needed (Using a modified die) but you can make it easy for yourself and get one of these sets
REDDING COMPETITION SHELLHOLDER SETS | Sinclair Intl
But if you have access to a lathe or a mate that works with one you can mod a spare shell holder and have it done the same day instead of waiting to get it in. ;)
This method is for those that neck size only, but you are now getting a tight bolt on when closing on an unfired necked case :-/ the shoulder needs bumping. If you have a comparator you use that to measure…. If not you can do it by feel and you get the best feel by removing the firing pin of your rifle so you are feeling the bolt closing on the case only.
You set your FL die up to size the case but back it out so the ram will stop short of the shell holder by about 15 thou, you can use shims like I did to lift it then reduce the size as you go
Skip's die shim kit - (7/8-14) | Sinclair Intl
Size the case and try to chamber without forcing the bolt and it shouldn’t close …unless you have mismatched shell holders or way to much head space, now you need to turn down the die a small amount at a time (or put a smaller shim in) sizing the case each time until you feel the bolt close with a bit of tension, Time to try a second case were the die is set as bumping a little at a time does not always move the case the same as one bumped from where it started. Try the new case in the rifle and what you are after is the slightest bit of tension on the bolt, you may need to tweak the setting to achieve this and test again with a new case. Compare it with no case to remind you what no tension feels like.
When you are comfortable with its setting and the dies lock ring has it locked in place you are set…..right… Not really ;D
Press stretch and uneven brass tension and uneven amounts of lube will still give you uneven sizing’s. You need the shell holder to bottom out without bumping the shoulder further, In my case I was going to modify the shell holder I was using to get mine right, you want a case in and size it, right at the top of the rams movement (some presses cam over so make sure it’s at the top of the stroke) measure the clearance between the shell holder and the die with a feeler gauge …but this will be for no clearance or even about a half a thou to long (the friction you feel) and my aim is for 1-2 thou clearance for easy bolt close and a little room for the case to move for easy extraction of a warmish load :P
http://i222.photobucket.com/albums/d...1-25143252.jpg
http://i222.photobucket.com/albums/d...e/IMG_9935.jpg
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This is where I took that shell holder to work, measure from the top of the shell holder to the face the shell sits on and I wanted to build that up the measurement less 2 thou, So I built up the top of the shell holder the popped it in the lathe and took some off until she was sorted :D
Why is it important? Well in a lighter weight barrel where harmonics are important different head space can shift POI 1 MOA or more, these are 4 shots with two different head spaces, 2 with a 1 thou crush and the other 2 were 2 thou clearance in 7mmSAUM . The same thing happens with my 243AI and to the same side with tight cases too.
http://i222.photobucket.com/albums/d...e/IMG_9988.jpg
this group was the 243AI when sighting in the better load, 2 shots then adjust left then 8 or so from memory, the one out to the left on its own was one that didn't get bumper and had about a 2 thou crush
http://i222.photobucket.com/albums/d...e/P8090065.jpg
This will not be for every one but I hope it helps some see the light.....and isn't to confusing :)
For the record I bump every firing with a body die and Collet size the neck ;)
