Shoulder bumping question

rjtaylor

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Feb 1, 2018
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31
Still trying to figure this out. I bought a Hornady headspace gauge but I don't know what I am looking for. It is for a 6.5 creedmoor but I don't know how far I am supposed to bump. Should I just take an unfired case measure it and bump my fired case back to that? Sorry for the remedial questions but my brain is on overload trying to get a handle on all of this.
 

J E Custom

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Jul 29, 2004
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As long as they chamber well there is no need to bump the shoulder.
the die maker should tell you the best way to bump with their dies.

If I have to bump, I just run the dies down until they touch and start screwing them down a little at a time testing the cases in the chamber.
As soon as they allow the bolt to close thats my setting. normally it is only a few thousandths that allows for brass spring back.

J E CUSTOM
 
Last edited:

ophious

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Jan 16, 2018
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Southern California
I take a measurement on my fired case using the shoulder datum line on the case. I'm looking for a Max .003" bump back. Any further is pointless and will wear your brass out quicker. Plus probably put your round out of specification. I shoot for a .001"-.002" shoulder bump. Once I have that dialed in to my die, I typically don't touch it. Just measure and adjust as needed. Also it's a good idea to adjust your expander ball at this point. After resizing a case, measure the neck diameter, zero out your calipers and then seat a bullet. Measure the neck again and hopefully your neck tension measurement will be around .0015" -.002" Polishing the ball might be necessary to get your neck tension right. Or you can always utilize a bushing die for resizing.
 

dok7mm

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west texas
As JE said, you want to make sure your brass has formed to your chamber, prior to bumping back your shoulder. When you start feeling resistance as you chamber fired brass, then you can bump back the shoulder +/- .002". Write that down for that rifle /brass combo.

Google Alex Wheeler's videos for a clear step by step demonstration of his method and you'll be gtg.
 

bigdaddyWSM

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Nov 15, 2009
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Location
South Dakota
A good rule of thumb is maybe on 2nd reload your brass should be well formed to your chamber, then if its a precision/target rifle bump shoulder back 1-2 thou from fireformed case, maybe 3-4 thou for a hunting rifle in case you get some dust/ piece of grass, etc in chamber.
 

rjtaylor

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Feb 1, 2018
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You guys are great. I appreciate the advice. I didn't realize how in depth this would be and my brain is hurting from everything I am trying to learn.
 

bigedp51

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Dec 10, 2010
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1,022
You do not need to fire the case several times to get the shoulder to max chamber length if full length resizing.

When full length resizing the case shoulder is squeezed upward in the die as the case body is reduced in diameter. And its possible to make the case longer than the chamber headspace and the case will not chamber.

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You can place a .010 feeler gauge between the die and shell holder and screw the die down until it contacts the feeler gauge on top of the shell holder. Then if the case does not chamber go to a thinner .008, .006, .004 etc until the case chambers without resistance. You can also buy Redding competition shell holders and do the same thing without adjusting the die.

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Skimafia

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May 10, 2018
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Location
Utah
I go by what ophious said. My goal with my 7SAUM is to bump the shoulder .002. Any more than that and I get a bit more case growth than I want. I want to minimize my brass stretching to avoid hardening.
 

Steve Baker

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Mar 23, 2018
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93
Location
New Mexico
I remove my pin and chamber mu cartridge. If it closes smooth I don't do anything. If it's not smooth I use Redding shell holders and bump the shoulder back in .002 increments until I get a smooth closing. I've been told this is wrong but it has worked for me just fine.
 
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