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Does this size bushing sound right?

pertnear

Silver $$ Contributor
I had my rifle re-chambered for 6BR no-turn for a varmint rifle. I ordered 50 Peterson cases to get me started. When figuring out the bushing size using the manufacturer’s formula with .003 tension & .001 spring back I get .264 which seems different than what most Lapua brass no-turn shooters are using. I measured the neck wall thickness of the Peterson brass right out of the box at a very consistent .0125”. Your thoughts?
 
I had my rifle re-chambered for 6BR no-turn for a varmint rifle. I ordered 50 Peterson cases to get me started. When figuring out the bushing size using the manufacturer’s formula with .003 tension & .001 spring back I get .264 which seems different than what most Lapua brass no-turn shooters are using. I measured the neck wall thickness of the Peterson brass right out of the box at a very consistent .0125”. Your thoughts?
What is the outside neck diameter of a loaded round?

Loaded round neck OD minus ( desired NT ) = bushing size.

Don’t calculate spring back
 
I use a .265 bushing and a .241 mandrel I have no idea what the actual neck tension is but it shoots one ragged hole with Peterson or Lapua brass
 
What is the outside neck diameter of a loaded round?

Loaded round neck OD minus ( desired NT ) = bushing size.

Don’t calculate spring back
Loaded round neck OD is .2662"
This is a hunting rifle with bullet off the lands. What would be a good NT?
 
Loaded round neck OD is .2662"
This is a hunting rifle with bullet off the lands. What would be a good NT?
For a hunting rifle where you will be working the round through a magazine I'd op for .003"-.004" neck tension. More tension keeps the bullet from being upset in the case and introducing runnout. If it's a single shot than Ok with .002" to .003". If you load into the lands a firmer grip on the bullet is desirable to keep the bullet at the initial measured seating depth. So for a .266" loaded OD you would want a .264" or .263" bushing for .002" or .003" neck tension.
 
Measure Loaded case neck diameter, Minus .002, example .268 loaded, need .266/ maybe.265 bushing for a ,272 No turn neck that gives .004 Total clearance devided by 2.
 

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