Sizing with bushing dies / Question

[500x]

This topic may have been covered numerous times, but my search turned up nothing informative. My question is when sizing with bushing dies and no expander, do the necks need to be skimmed with a neck turner to true all to a uniform size? I may be dead wrong, but it seems to me if you have even a slight variance in neck thickness it could cause a problem with more tension in one spot when the bullet is seated/fired. Informative input would be greatly appreciated. It's Lapua brass in a 6 dasher .272 neck, Redding F/L type S die. Thanks, Mark

 

[Steve Blair]

Even with an expander, brass springback is not uniform and can result in variable neck tension. Your thinking is correct. If you want the most consistent neck tension, turn the necks enough to clean up any wall thickness variance, size only as much as required and anneal when cold-working hardens them.

 

[Winchester69]

Hold a piece of string using both hands. Pull against the opposite hand, putting tension in the string. Is the tension uniform? Tie some knots in the string and again apply tension. Does the tension now vary according to the placement of the knots?

 

[necchi]

winshester 69,,,What?

 

[fdshuster]

Mark: Good question you've raised, and I'm sure will generate many different (and reasonable) viewpoints. My Lapua brass in 220 Russian, 6BR, 222 & 223 Rem, and 308 all have a maximum neck wall thickness variation of .001", and I'm comfortable working with that "as-is" for the no-turn necks. If it exceeded that, then yes, I would do a minimum clean up cut, taking off the high spots. Some weigh brass cases and primers, segregate match bullets for weight differences, etc., so the answer, I think, may be "how far do you want to go", ( in the search for accuracy)? Interesting point, may be the basis for some side-by-side comparison testing to see how much it effects group sizes.