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what to do with cases with excessive neck run out?

 
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  #8  
Old 01-02-2012, 01:07 PM
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Re: what to do with cases with excessive neck run out?

One thing to look at is a expander mandrel die from sinclair. Got one awhile back and works great. You wouldn't think the expander mandrel could help all that much opposed to a normal die expander but it works. I had runout when necking 7 WSM up to 338 until I bought one with a 30 and 338 mandrel. Just my 2 cents.
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Old 01-02-2012, 01:09 PM
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Re: what to do with cases with excessive neck run out?

With proper neck turning all your necks will have uniform thickness. I prefer .015 neck thickness and then neck size with .002 tension.

If you cull cases, do so after you have all the external dimensions uniform including primer pockets and flash holes. Then measure weight and segment your brass by weight.

Neck turning is necessary for maximum bullet concentricity and is even more important when necking up or down brass.
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Old 01-02-2012, 05:15 PM
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Re: what to do with cases with excessive neck run out?

Neck turning only gets a small portion of the case uniform. The rest of that case length is still not uniform, and this combined with cycling of it(sizing/firing), allows cases to end up bananas as measured on a runout gage.
Now if you didn't size all that length, fireforming would put it fairley straight where it would remain so. But I suspect you will have to FL size those cases eventually and from then onward.
This is why I think you should measure thickness variance(as seen in the necks), and keep only cases under 1thou in 360deg variance. You need a ball mic with a stop for this.
These would be cases to further prep, and neck turn.

I damn sure wouldn't generalize capacity by Remington brass weight..
After prepped, fully fireformed, & before any sizing, just measure it's H20 capacity and again cull offenders.
I imagine Rem brass is dirt cheap and would consider it disposable. And matched brass is gold regardless of brand, so you've got nothing to lose really.

I agree with frank7mm about the Sinclair expander die system. It is by far the best expansion short of fireforming.
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Old 01-03-2012, 09:26 AM
cbb cbb is offline
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Re: what to do with cases with excessive neck run out?

Thanks for your help. I have a better understanding of the process now.
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  #12  
Old 01-03-2012, 09:36 PM
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Re: what to do with cases with excessive neck run out?

Fireforming will get the case uniform IF it has equal dimensions in wall thickness. If not, it will be banana shaped and nothing can fix that.

Get rid of the expanding mandrel in the FL die and go to a straight decapping stem and runout will cease IF it is die related.

All brass is beat to hell when it comes out of a bag. Use the expanding mandrel to take the dents out and resize down to the dimension you need.

The use of the Sinclair or K&M expanding mandrels is all you need to maintain neck expansions in lieu of the die expanding mandrels.

Contrary to some, NS is not the wonderful panacea as touted. IMO it is a poor excuse for not getting rid of the expanding mandrel and will lead to work hardening of the brass and vast variances in the brass as the brass grows until you get the dreaded bolt "click" and hard opening. Worse yet, you get hard chambering on the hunt. By then, too late, the brass has work hardened and you will have trouble from then on maintaining uniformity. NS only results in unreliable functioning and and wide variance in brass. Very few people actually measure cases with an accurate blade mike to actually measure brass variance. Try it some time and watch the brass grow dimensionally on NS only brass vs uniform FL sized brass with a dimensionally correct FL die.
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Old 01-03-2012, 09:41 PM
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Re: what to do with cases with excessive neck run out?

I have had excellent results when sizing to cycle the case up into the die, then rotate the case 90 degrees and repeat. I've seen this simple process work wonders when sizing. When I seat the bullets I rotate the case approximately 90 degrees 3-5 times while seating and that too helps to obtain low runout. You definately want to at least take the high side off the necks too.
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  #14  
Old 01-04-2012, 01:35 AM
cbb cbb is offline
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Re: what to do with cases with excessive neck run out?

Update, I ran less beat up new 300 Rem ultra mag brass through a standard RCBS die just over the sizing ball to make it more uniform 30 cal opening. Neck run out was typically 0.002, surprising me. I then ran it over the redding die mandrel to neck up to .338 size. It has a longer sizing mandrel compared to the RCBS (0.375 vs. .053 of visualized brass contact area.) The force needed on the handle of the press to neck up seemed more consistent having made the 30 cal opening more consistent before necking up in size. I think I will do this again if for no other reason than it made me feel warmer inside. It may also have helped run out, but I was also using brass that was in better shape.

I picked up run out when necking up. I tried rotating, I tried running the mandrel up higher in the die, I floated the stem, I floated the die, I floated both, etc. I was unable to improve my run out in this step - .001 to .008. (But, much better than before with rougher brass)

Due to the force involved in necking up, I could have picked up run out in several places. Case just a little out of line in shell holder, shell holder not exactly square to ram causing some cant of the case, ram of press wobble as I push brass up, base of brass not square to rest of case - allowing the stem to float should help in these areas as I understand things. It may also be due to neck wall thickness variances causing the neck to stretch out a little more on one side than another. Maybe the Redding mandrel is not as good as the Sinclair. In my case, I'm guessing it was mostly the the brass and how and where it wanted to stretch- thickness related in the neck and possibly other areas of the case to a lesser extent as the case body of this new brass is not touching the die body when the neck is going over the sizing mandrel.

Anyways, I ended up with 53% of my brass .004 and under, 80% under .006, and 100% under .008. Still not sure if that is good or bad yield on new rem brass when necking up. I am going to finish loading some of my best cases, try to correct any bullet run out with a Hornady concentricity gauge, and shoot a few rounds this weekend!

Once again, please point out any misunderstandings in my thinking. I realize that I may not have it all straight and welcome your thoughts. Thanks for you help and your time. Casey
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