Case neck turning & neck tension

[Bad Ass Wallace]

Got to thinking about the internals of my 30.06 springfield particularly in the neck area.

I shoot a Lyman 311284 which cast in WW comes out of the mould .310. I lube in a .310 sizer. If the standard jacketed bullet is .308 then upon firing, the case neck expands to let her go. With cast, the amount of expansion is reduced because the bullet is already .002 oversized.

Recently I started outside neck turning .004 off each case and using a neck expander from CH that is .309 rather than the RCBS expander which mics .305. I thought that .001 would allow the boolits to fall out of the case but they are quite firmly held.

Grouping has tightened considerably from 1.75MOA down to 1.1MOA with a more than occasional sub MOA cluster.

My other bench gun is a 7x57 Mauser and I can't wait to see if proper neck tturning and a larger expander will net similar results?

http://img.photobucket.com/albums/v152/BAWallace/Springfield_cast.jpg

[KevMT]

BAW,

Seems as though I read an article by Mountain Molds where he was using considerably oversized bullets in an 06. Seems he had plenty of throat room to use a .314+ boolit but he found that when he pulled down some assembled rounds he the now undersized cases had resized the boolits. I wonder if the same was the source of the improvments in your loads? I've been considering having a custom M die spud made at about .308 for the same reason.

[StarMetal]

Well it all stands to reason that if the case neck is and it tension are stronger then the alloy that it will size the bullet down some.

Joe

[Willbird]

Also by tirning the necks you are indrectly reducing the amount the die sizes them down before opening them back up with the expander ball. The same effect might be seen by using a bushing type full length or neck die.

Bill

[felix]

Yes, neck turning cases is a great start to getting improved accuracy, but only in guns that can appreciate it. That has to be tried out for each gun. It depends on how round the chamber is and how round the cases are from the start. A really round case will have really round necks on average, and that is why the BR folks are very case quality folks. Turning the necks on a round case mates the neck to the bullet, the bullet to the chamber. When this process is done for non-round cases, the case necks have to be re-checked every so often. If not, accuracy will go south in time "for no reason". .... felix