Bushing size selection

[Vesterhoff]

So i'm looking for a bushing die to use for 6.5 creedmoor Lapua brass, and i've decided on the Redding Type-S Full size bushing die.

The problem is delivery-time, and price, before these things hits Europe, so i would like to order the correct bushing size the first time. So witch bushing/bushings to order?

A good advice would be very much appreciated.

 

[Jud96]

Take a virgin case, seat a bullet in it. Then measure the outside diameter of your case neck. For example, if it's 0.290 and you want .002 neck tension, you need to order a .288 bushing.

 

[Vesterhoff]

Take a virgin case, seat a bullet in it. Then measure the outside diameter of your case neck. For example, if it's 0.290 and you want .002 neck tension, you need to order a .288 bushing.

A virgin case without any kind of prep'?

 

[Jud96]

Yeah just seat a bullet in it. It doesn't matter what the factory set the neck tension at, you just want the outside diameter of the neck with a bullet seated in it.

 

[Hairtrigger]

A virgin case without any kind of prep'?

Unless you are turning the neck

 

[Kanoeking]

Or you can use a ball mic and measure the brass thickness at the case mouth, double it, add your projectiles thickness and then subtract your desired neck tension for your correct bushing size. Case wall .010" x 2 = .020", .020" + .264" = .284". If you want .003" of neck tension you'd take that .284" - .003" and get a .281" bushing. Either way you skin the cat you have to bear in mind, each lot of brass may vary enough to require different bushings.

 

[elf]

All good anwers. I always order 2 or 3 bushings: One at your measured diameter and two more- one above and one below that number. After shooting each, you can decide which will work best.

 

[Hairtrigger]

Those bushings are priced about 3x more than that should cost

 

[Vesterhoff]

Those bushings are priced about 3x more than that should cost

And even more when they have been shipped across the Atlantic

 

[Mikecr]

Subtract 2thou from loaded neck OD (measured or calculated).
That's a baseline bushing selection, given a chamber neck clearance around 3thou.
This would provide 1thou interference for seating bullets.
You can then adjust neck tension via LENGTH of that bushing sizing.

If your neck clearance is higher, subtract only 1thou from loaded OD.
The greater downsizing will roll brass at a higher angle, reducing the neck more than stamped on the bushing.

If you don't know chamber clearance, you can order both bushings.
One will provide a better result than the other.
There is no credible reason to excessively downsize necks, so forget any of that. Your expansion, button, mandrel, or bullet, would just undo it anyway.