False Shoulder for 6mm Dasher

[Curmudgeon]

Hello, I am close to my Dasher build. When I create a false shoulder by sizing brass to
6.5 how long should the neck be when I downsize to 6mm? I understand the Dasher has a short neck, can I size the neck with the bushing I will use for a no turn neck?
Thanks and cheers.

 

[tenring]

You can use the bushing in a 6BR sizer die (not a Dasher die). After expanding the necks to .264, remove the bolt firing pin. Lube the case and insert in the action. It will not chamber. Now, run it up about 1/4" into the 6BR bushing die. Gently try to chamber, and it will not. turn the die down about 20 degrees at a time, until the case will enter the chamber with a feeling of being snug. Set the die there and continue with the entire batch of brass.

After all are sized in this fashion, you are ready to fireform by shooting or use the COW method.

 

[alf]

I generally just neck up to 25 caliber, then size it back down with my Dasher die and correct bushing, to get a crush fit for fireforming described by tenring.

 

[Gabe22BR]

I used a 6.5 expander from Sinclair. Then used a F/L bushing die in dasher. I set mine so I could just close the bolt.
I used 12gr. of blue dot, and stuffed them with 2"x3" paper towels stuffed full. Nothing to clean out of the action, and barrel, but carbon. Carb-out cleaned that with a mop.

 

[LRPV]

What benefit do feel you get by necking up to 6.5 rather than just .257? Just curious if there's a reason or if it's just what you had to start with and never changed.