Proper neck bushing?

[oklarcher]

Ive been reloading for 10 + years and just started useing full lenght bushing dies. What is the most accurate way to measure case necks for the proper bushing without a ball mic? Redding suggest measuring a loaded round and subtract .001 for spring back. I run my new brass over my expander ball when it is new to straighten my necks. I like to run .003 bullet tension.

Thanks, Scott

 

[boomtube]

"Redding suggest measuring a loaded round and subtract .001 for spring back."

Maybe Redding knows what they are talking about?


"I run my new brass over my expander ball when it is new to straighten my necks."

Expander balls are THE major contributor to bent necks. Their elimination is what drove the development of bushing dies. (Problems with bushings is what drove Lee to develop their Collet Neck Sizer die, works good too!)


"I like to run .003 bullet tension."

At 3 rhou, I believe you will find your loaded ammo to be no more concentric than it was with a conventional sizer. One, or maybe two thou might well be better.

 

[oklarcher]

I think you are right about redding and the method they use to detirmine proper bushing size. Im useing a redding die. I was wondering if I run my new cases over an expander ball for the first time and then load a round and take the measurement. Will this be correct? Can I take a fired case from my chamber and subtract .004 and get the size bushing needed? An expander ball can over work case necks and hamper case life. I only want to run my new ones over an expander ball once to straighten dings and dents from shipping and handling. How much bullet tension can you expect from useing just a standard full length sizeing die? I typically use Norma, Lapua, and Nosler brass. I am probably making this more difficult than it is. So if I change brass to a different lot or type my bushing will have to change because neck thichness will vary? I thought I might mention these are hunting rifles thats why i prefer .003 tension.

 

[AJ Peacock]

I think you are right about redding and the method they use to detirmine proper bushing size. Im useing a redding die. I was wondering if I run my new cases over an expander ball for the first time and then load a round and take the measurement. Will this be correct? Can I take a fired case from my chamber and subtract .004 and get the size bushing needed? An expander ball can over work case necks and hamper case life. I only want to run my new ones over an expander ball once to straighten dings and dents from shipping and handling. How much bullet tension can you expect from useing just a standard full length sizeing die? I typically use Norma, Lapua, and Nosler brass. I am probably making this more difficult than it is. So if I change brass to a different lot or type my bushing will have to change because neck thichness will vary? I thought I might mention these are hunting rifles thats why i prefer .003 tension.

You can run new brass over an expander ball to make the necks 'rounder' not 'straighter' (I'm sure that's what you meant). The easiest way to figure the bushing is to measure your loaded rounds and subtract 1-2 thousandths. I just measured some of my 300wsm's and compared to the bushing I use and it is .0015" smaller than the loaded round. Any more than .002" and you're just over working your brass. I like to have 3 bushings for my cartridges, then I have them on hand for different brass (.001, .002 and .003 under loaded size). There is a small green box made for holding the bushings. I have bushings for my 7mm's, .30's and 338's.

Just take a measurement and get 3 bushings that bracket the .001 - .003 under loaded size. Then install the middle one and see how it works.

Good luck,
AJ

 

[canderson]

Sorry, to hijack and ask another question. When you are running the bushing dies with neck turned brass, do you use the expander at all? Are the necks concentric after turning and there is no need?

Thanks,
Chris

 

[woods]

Redding suggest measuring a loaded round and subtract .001 for spring back. I run my new brass over my expander ball when it is new to straighten my necks. I like to run .003 bullet tension.

Thanks, Scott

IMO, that's not exactly right (and yes Redding does know what they are talking about but maybe you misquoted them). If the outside of a 30-06 loaded case was .332" and you got a .331" bushing then when you sized the case neck and it sprang back .001" it would be .332". You would have 0.000" bullet grip. To me it would be correct to say "Measure a loaded round neck OD, subtract the bullet grip you want and subtract another .001" for springback".

Can I take a fired case from my chamber and subtract .004 and get the size bushing needed?

No, the brass will expand to the size of your chamber which may be up to .010"+ over the loaded OD of your brass.

When you are running the bushing dies with neck turned brass, do you use the expander at all? Are the necks concentric after turning and there is no need?

Most do not use the expander. If you are going to size the neck smaller and then expand it with the expander ball then you might as well use a much cheaper FL die. Also using an expander ball will work harden your necks twice as fast as just using the bushing without the expander.

No the necks are not necessarily concentric after turning, you can turn the necks and still have runout. If the neck was not concentric before turning then the outside neck turner will not necessarily realign the neck with the case body, it is made to make the neck brass thickness consistant only. Also if the brass has a large variance in neck thickness then turning will not center the neck with the case body

 

[boomtube]

" Can I take a fired case from my chamber and subtract .004 and get the size bushing needed?"

Yes, IF your chamber neck is exactly .003" amount over the loaded round size. That's not likely! So, NO.

Do as Redding suggests. Forget all the calculations, just make a few dummy loaded rounds, mike the necks, average the numbers and order a bushing that's 2 and/or 3 thou under. After "spring back", your necks should be about right. On average.

NO ONE can tell you exactly what you need to do, only you can find the magic number for your die, cases, rifle. And that number will change somewhat as the brass work hardens! AAARRGGH!

I prefer the simplisity of a Lee Collet die. It insures straighter necks and makes the inner hole the same diameter no matter any variations in the brass.

 

[oklarcher]

Thanks for the help guys i now see the light.lightbulb