# bushing size vs neck thickness variance

1. ### arrowWell-Known Member

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I am shooting norma brass out of my .300 win mag and using Redding Bushing neck sizer die. I was going to use the mic and sort the brass into lots depending on the neck thickness. I started doing this and I figured out really quickly that it wasnt going to work due to the variances of the neck thickness on each piece of brass. I will check 3 places around a neck and get readings from .0140 to .0148 or so and the next one will be .0146 to .0153. I am not concerned with these numbers exept I dont know what bushing to use. I could take an average of .0145" X 2 = .029. .029 + .308 = .337. So .002" neck tension would be a .335" bushing however on the low end of thickness .0140" this would only be .001" neck tension which is not good for a magazine fed rifle. So I could go .334" bushing for the safe side then on the high end of lets just say .015" that would be .004" neck tension which is getting pretty high. Like I said I was going to sort them into different lots but they are all about the same but just depending on where on the neck you measure I get a different thickness.

I know neck turning would alleviate this whole problem but i have been there so many times and everytime I just end up ruining good brass and get a headache and loose sleep over all the brass I ruined. So other than neck turning, what are my options?

2. ### woodsWell-Known Member

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You could use the expander that came with the die. IOW if the expander mic's .305" then get a bushing that will size the necks of the THINNEST brass to .001" below the diameter of the expander.

At least all your brass would then have the same ID

3. ### arrowWell-Known Member

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Thanks for the advise. That is a good idea but I have heard some bad things about the expander plug. Are there any other ideas out there. How does everyone else do it?

4. ### TOM HWell-Known Member

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If your necks are between .0140" and .0153" taking .0013" off the thickness shouldn't be a problem or ruining necks.

Since your not going to clean up the necks your going to have to buy few different size bushing and see what works best in your rifle. What I do is sort some brass and load some bullets mike outside dia see what you come up with and average that. Whatever that bushing size is you might want to get extra +/- bushings.

I only size about half the neck with my bushing dies. Well good luck

5. ### 7mmRHBWell-Known Member

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Arrow, seat a bullet, preferably one that you are going to use for load dev, then measure the neck diameter with good calipers. Take the resulting number and buy bushings that are .002, .003 .004 smaller than the neck dimension and you will have the correct size covered.

The .003 and .004 are usually better for hunting rounds to be fed from the mag box ( you don't want your bullet to be able to move back into the case under recoil ) and .001 and .002 could be the best if shooting single shot or for target shooting. ---- RHB

6. ### MikecrWell-Known Member

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What are you measuring with?

7. ### arrowWell-Known Member

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Rcbs ball micrometer.

8. ### MikecrWell-Known Member

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Have you put a stop on it to set your datum?
Example:

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9. ### arrowWell-Known Member

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That stop is a good idea. I will try that. Thank you.