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Old 11-20-2018, 09:14 AM
eschafer eschafer is offline
 
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Default sizing .300wm brass to .338wm?

Wondering how many members do this?....
I recently purchased a bag of 50 Winchester .338wm brass from a member on CGN.... I was elated to have more brass for my rifle but when I measured the new Win cases, they were consistently 0.015"-0.017" shorter from base to shoulder than were cases once fired from my own .338wm chamber....

I understand on first firing they would headspace on the belt... But, 0.017" stretch to form seems quite excessive... Of course, on subsequent reloading I could better match the size of case to my chamber as the brass will now be formed more closely to fit the chamber...

Would it not be worth the effort to size and neck up .300wm brass to fit my .338wm chamber? (.330wm brass is longer from base to shoulder).. Using this strategy, I could have the case better fit my chamber for first firing, maybe keep accuracy for first firing a little better and save the dreaded stretching near the belt, down to a minimum....

If my thinking is flawed suggest so.... If this is a practice often performed, please let me know of your procedure as I'm willing to try anything which does not compromise safety...

New to reloading but willing to learn all I can...

I make my case measurements with a Larry Willis Digital "Headspace Gauge" (which is really just a digital comparator)... Thanks in advance...
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  #2  
Old 11-20-2018, 10:11 AM
Pathfinder76 Pathfinder76 is offline
 
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Open the neck to 35. Then resize neck back to 338 until you creat a false shoulder.
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  #3  
Old 11-20-2018, 01:03 PM
brewster29 brewster29 is offline
 
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You would be better served starting with 7mm Rem Mag brass as it is dimensionally identical to 338 WM except for the neck diameter. You would have to trim 300 Win brass to length.
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Old 11-20-2018, 01:09 PM
obsessed1 obsessed1 is offline
 
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Quote:
Originally Posted by chuck View Post
Open the neck to 35. Then resize neck back to 338 until you creat a false shoulder.
This is the correct answer. I do this with all.My new 300 wm brass
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Old 11-20-2018, 03:41 PM
eschafer eschafer is offline
 
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Quote:
Originally Posted by chuck View Post
Open the neck to 35. Then resize neck back to 338 until you creat a false shoulder.
This is the correct answer. I do this with all.My new 300 wm brass


As I'm quite new to this, and learning each day at my press, I need a few more details.... Do I need a new die with .35" neck or do I buy only another expander to put into my .338 wm die to neck up prior to sizing?

Thanks in advance....
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  #6  
Old 11-20-2018, 03:56 PM
fps plus fps plus is offline
 
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Simply seat the bullets into the lands with a mild charge and shoot
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  #7  
Old 11-20-2018, 04:36 PM
obsessed1 obsessed1 is offline
 
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All you need is a 35 expander ball. Run it in your due to open up the mouth then replace your 33 expander and set your die. Set your die so it creates a false shoulder ( keep chambering in your rifle until you get a slight crush when closing on the case). This will allow the case to blow out to your chamber without stretching.
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Old 11-21-2018, 10:44 AM
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Dean2 Dean2 is offline
 
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Quote:
Originally Posted by obsessed1 View Post
All you need is a 35 expander ball. Run it in your due to open up the mouth then replace your 33 expander and set your die. Set your die so it creates a false shoulder ( keep chambering in your rifle until you get a slight crush when closing on the case). This will allow the case to blow out to your chamber without stretching.
This will work but you have to short stroke the handle. You run it over the 35 expander and you would have to stop right after it goes over it, before you get to the top of stroke. Once you have opened up all your cases then put the 33 expander button back on and FL size your cases but set the die high enough that the round will chamber but you don't fully size 100% of the neck. You want a small bit of the neck to still be 35 caliber, that is what is referred to as the false shoulder.

Picture I borrowed from the net.

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Old 11-21-2018, 01:21 PM
qwert qwert is offline
 
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Quote:
Originally Posted by Dean2 View Post
This will work but you have to short stroke the handle. You run it over the 35 expander and you would have to stop right after it goes over it, before you get to the top of stroke. Once you have opened up all your cases then put the 33 expander button back on and FL size your cases but set the die high enough that the round will chamber but you don't fully size 100% of the neck. You want a small bit of the neck to still be 35 caliber, that is what is referred to as the false shoulder.

Picture I borrowed from the net.

Dean2’s photo didn’t last long!!! (But a link is in the reply screen, but not the preview.)

A Google image search on “false shoulder” will find many similar, as well as much more information and discussion of the procedure.

Many RCBS type neck expanders are ‘buttons’ or ‘balls’ with very little taper, they are not designed to expand a case neck more than a few thousands of an inch, and may require application of high force which can cause the neck to become non-concentric, particularly if the neck wall thickness is non-uniform. Lube can help reduce this, but
IMHE a better solution is to use an expander with a long taper like a Lee (very long taper) or Hornady (shorter more droplet shaped taper).
Hornady sells threaded rods (# 390969) to allow their expanders to be used in RCBS threaded dies.
Some expanders can be used or adapted for use in other die bodies such as larger caliber, or universal neck, or expander, or de-priming dies.
Alternatively, a suitable 7/8”x14tpi bolt can be turned on a lathe to make an expander mandrel of any size and shape required.

Those who purchase factory loaded ammo, (especially belted case), with the intention of saving brass for reloading, may wish to consider pulling the bullets, then forming a false shoulder to cause the case to properly headspace on the shoulder on first firing and reduce or eliminate the case stretching from initial fire-forming in a long headspace chamber.

Previously fired (and possibly unfired factory) brass may benefit from proper chamfering of the case mouth, and annealing of the neck and shoulder before expanding and fire-forming.

Good Luck, YMMV.
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  #10  
Old 11-21-2018, 06:47 PM
obsessed1 obsessed1 is offline
 
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Quote:
Originally Posted by Dean2 View Post
This will work but you have to short stroke the handle. You run it over the 35 expander and you would have to stop right after it goes over it, before you get to the top of stroke. Once you have opened up all your cases then put the 33 expander button back on and FL size your cases but set the die high enough that the round will chamber but you don't fully size 100% of the neck. You want a small bit of the neck to still be 35 caliber, that is what is referred to as the false shoulder.

Picture I borrowed from the net.




Exactly what I do. You just explain it better:-)
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  #11  
Old 11-24-2018, 06:50 PM
eschafer eschafer is offline
 
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Thanks for all the replies.... Just need one more clarification with regards to short stroking with a .35" expander and creating a false shoulder....

I'm assuming that this technique is suggested to be used on my new (short from base to shoulder) 338 wm brass.... and suggesting I forget my original inquiry of trying to form 300 wm brass to .338wm, correct? Please bare with me... Very new to this.... Thank you to all...
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  #12  
Old 11-24-2018, 07:09 PM
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Dean2 Dean2 is offline
 
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Quote:
Originally Posted by eschafer View Post
Thanks for all the replies.... Just need one more clarification with regards to short stroking with a .35" expander and creating a false shoulder....

I'm assuming that this technique is suggested to be used on my new (short from base to shoulder) 338 wm brass.... and suggesting I forget my original inquiry of trying to form 300 wm brass to .338wm, correct? Please bare with me... Very new to this.... Thank you to all...
This technique works for 300 or 338 brass. The only diferrence is with 300 brass you need to open it up to 328 in the first step. Trying to go to 35 in one step is too big a jump. If u start with 300 just expand it to 338 first then to 35.

I have expanded 340 to 460 but I did it in 3 steps. First 375, then 416 then 458.
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