Recommend a neck size and bushing please

[widmn]

I was thinking about a neck size of .294 for a 6.5x284. Using Lapua brass and 142 SMKs.
What size bushing for the type S neck dies and finished size do you folks recommend?
Thanks

 

[mikecr]

What's the chamber neck suppose to be? How thick is the brass in the necks? Or how bout a fired neck measurement.
With is information you may have determined .294" was appropriate for 2-3 thou of bullet tension and 1-2 thou chamber clearance. Not sure.
But you can get unseated necks measuring .294 with a .293 bushing.
Brass thickness + .264" will be the loaded neck dimension.
With my 26cal, I get .001" springback. This, with Winchester brass @.013" thick in the neck.

 

[Forum Boss]

As MikeCr notes, it's best to measure the outside neck diameter of a loaded round. Then, as a starting point, I'd use a bushing that is .002" under that diameter. You may find, however, that a .001" undersize bushing produces better accuracy. If you have turned necks, or use moly bullets, a .003" undersize bushing may work best. Different loads will have different preferences. That's why many Type 'S' bushing die users have multiple bushings.