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neck sise and sholder bump

 
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  #1  
Old 10-07-2011, 10:27 AM
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neck sise and sholder bump

I have switched to neck sizeing in all my bolt action rifles with great results. Just wondering is I should be full sizing after a number of fireings in order to bump the sholder back. I have had some cases that were siticky during retraction even at min load specs with cases properly trimed. What is the correct way to measure sholder bump? Is it manditory to use a FL die to bump sholder? Is there specail die set up when bumping scholder? ANY IDEAS? Thanks
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  #2  
Old 10-07-2011, 11:11 AM
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Re: neck sise and sholder bump

It's normal to reach a point where shoulder bumping is needed.
You don't have to FL size cases for this, and can just bump as a seperate independent operation with a Redding 'body die'(unless it's an unusual wildcat).

There are tools just for checking shoulder movement called headspace gages. These provide for a relative measure/datum on the shoulders, and you can use one to measure the difference between good chambering and bad chambering of brass. You set a body(bump) die & size until you achieve ~1-1.5thou under zero headspace. This should chamber well.
You don't want to oversize this as excess headspace causes brass to stretch back against the boltface(increasing it's length and challenging the action integrity).
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Old 10-07-2011, 10:54 PM
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Re: neck sise and sholder bump

Quote:
Originally Posted by Mikecr View Post
There are tools just for checking shoulder movement called headspace gages. These provide for a relative measure/datum on the shoulders, and you can use one to measure the difference between good chambering and bad chambering of brass. You set a body(bump) die & size until you achieve ~1-1.5thou under zero headspace.
The reloading industry calls tools that measure the head to shoulder distance a case gage; sometimes a case headspace gage. Headspace gages measure the rifle's chamber from the bolt face to the point in the chamber that stops the loaqded case from going too far forward. That chamber point is also where the case stops as the firing pin drives it forward and firing the primer.

With such a gage, such as the RCBS Precision Mic, you can measure fired cases and set a full length sizing die to set their shoulders back 2 thousandths; about right for all bottleneck cases
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Old 10-08-2011, 04:47 AM
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Re: neck sise and sholder bump

I like the Redding Instant Indicator for measuring bump. Have three of them. Unfortunately, they are caliber specific.
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  #5  
Old 10-12-2011, 03:30 PM
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Re: neck sise and sholder bump

If I dont have any of those fancy tools will a full length size push the sholder back.
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  #6  
Old 10-12-2011, 03:45 PM
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Re: neck sise and sholder bump

Yes, but you won't know just how much. Invest in one of the gages, even one of the cheaper ones, and you'll be ahead of the curve. Need to know what you're moving here, and the only way to do that is to measure it. That's where the gages come in.
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Old 10-12-2011, 04:06 PM
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Re: neck sise and sholder bump

Quote:
Originally Posted by Kevin Thomas View Post
Yes, but you won't know just how much. Invest in one of the gages, even one of the cheaper ones, and you'll be ahead of the curve. Need to know what you're moving here, and the only way to do that is to measure it. That's where the gages come in.
Kevin's absolutely right on this one.

The reason is, depending on how much case lube's on the fired case and the difference in diameters of the fired case and die, you can easily have a spread across two dozen cases of 3 to 6 thousandths of shoulder set back. Good case cleaning and lubing processes can get the spread down to under 3 thousandths.

When you get the case gage, use it to full length size your cases such that the ones with the highest sized case headspace reading is about 2 thousandths shorter than the average reading you get from measuring several fired cases. This insures that all your cases will chamber easily. And even the ones that had their shoulders set back the most will still be safe in your rifle.
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