Does this size bushing sound right?

[pertnear]

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?

 

[fkimble@charter.net]

Total neck wall thickness is .025 plus bullet .243 = .268 minus .003 tension = .265.

Frank

 

[JFrank]

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

 

[dusterdave173]

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

 

[pertnear]

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?

 

[LCazador]

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.

 

[varget204]

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.