- Thread starter BrentMac
- Start date
The best way to go about this is to measure a loaded round and subtract the amount of neck tension you want to run.
It sounds like you dont have a loaded round, so you can calculate it if you measure the neck thickness.
Take Neck Thickness x 2, add diamter of your bullet, and subtract .0015.
It sounds like you dont have a loaded round, so you can calculate it if you measure the neck thickness.
Take Neck Thickness x 2, add diamter of your bullet, and subtract .0015.
I'm just getting started with a 6mm Creedmoor. I bought some Lapua bras and seated a Berger bullet and measured the outside neck diameter. I ended up getting a 0.271" bushing. I haven't resized any necks yet so I haven't proven my choice out.
I don't have a mic but if I take the outside diameter, subtract the bullet diameter, and divide by 2, I get 0.1475".
I reload 6mm CM and with a tubing mic my Lapua brass neck thickness measured 0.0135" and my Hornady brass neck thickness measured 0.014".
For 0.002" neck tension I bought both 0.268" and 0.269" bushings.
But I also use a Sinclair mandrel after sizing to get consistent neck tension. I have found enough variation of the neck wall thickness which I believe leads to a slight inconsistency in neck tension if the cases are only sized with a bushing which is only reducing the outer diameter. This does vary even with Lapua brass unless the necks are turned.
For 0.002" neck tension I bought both 0.268" and 0.269" bushings.
But I also use a Sinclair mandrel after sizing to get consistent neck tension. I have found enough variation of the neck wall thickness which I believe leads to a slight inconsistency in neck tension if the cases are only sized with a bushing which is only reducing the outer diameter. This does vary even with Lapua brass unless the necks are turned.
