Neck Bushing Question

Hunt5BN

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Jul 29, 2015
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Location
AZ
Hope someone can help me with a neck bushing question.

Background: I am loading .308 Winchester using Lapua brass and Hornady 178-gr ELD-x bullets. The loaded rounds have a neck diameter of .337. I am using a .335 bushing in a Redding die. Prior to resizing a spent casing the neck diameter is .340. Once I FL resize the brass with the .335 neck bushing (no expander button) the neck measures .332-.333. Shouldn’t it come out as .335?

The only change I have made in my reloading process is I sent the spent brass out to be cleaned and annealed.

Thanks in advance!
 

nksmfamjp

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Jan 5, 2004
Messages
672
IME, it should come out 0.335-0.336”, but this is why they make the sizes! 0.333 is 0.007” neck tension. I would try a 337 and 338.

i have a 337 for sale....
337 for sale
 

Mikecr

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Aug 10, 2003
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5,301
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A .335 bushing should hold that ID, but it won't mean necks will size & springback to exactly .335 with it.
Also, by 5thou of neck sizing the results are lower than stamped on the bushing because the higher sizing angle rolls brass further inward. Take that .337 bushing sale!
 
Last edited:

aushunter1

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Nov 16, 2012
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Australia
Once I FL resize the brass with the .335 neck bushing (no expander button) the neck measures .332-.333. Shouldn’t it come out as .335?
If your removing the button expander imo the neck will always be over sized, that what the expander is supposed to do, bring it back to an acceptable diameter otherwise you will have to much tension.

I know people dont want to use factory die expanders so as to reduce runnout but you still need to use an expander, whether its a precise .001 or .002 mandrel.
 
Last edited:

Frank Kalisz

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Oct 1, 2018
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Indianapolis
for what it’s worth I use a custom honed Forster FL die without expander spindle sized at 0.334” for my 308 Lapua brass. What you’re doing is really no different than me. I think you’d be doing great if you do another step with a mandrel die.

It’s also good to turn necks on all your brass to make sure all neck sizing is consistent. I use a Forster “Original” lathe trimmer to turn necks of all my 308 brass to 0.014” thick.
 

Frank Kalisz

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Oct 1, 2018
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Location
Indianapolis
You can also get pin gauges to check your inside neck diameters. They’re cheap on amazon. For my 308, I have “minus” pin gauges at .3050, .3055, .3060, .3065 & .3070.

My FL die gets my 308 brass to between .3055 and .3060, and my 21st Century mandrel gets them to between .3060 and .3065
 

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