Turn the necks then fire form, or vice-versa?

[cbonner]

I necked down Norma 300 WSM brass to 7mm, to be used in my Kimber 7WSM rifle. I noticed the shoulder for the resulting cases will need to be pushed out to the demensions of the 7WSM chamber,the 300WSM has a longer neck). I intend to very lightly turn the necks, but am wondering if this should be done before, or after fire forming the cases. Anyhow, any advice would be greatly appreciated.

 

[mikecr]

I always complete all brass prep, including turning, prior to FF.
Necking down will increase thickness in the necks. Depending on your chamber, you may not have clearance to FF without turning anyway.
After turning you can neck up, and partially size back down to form a false shoulder for your first firing.
You might also find,depending on your turning mandrel/expander) that turning at 300wsm standard, then sizing down produces better consistancy than you can achieve if turning at 7mm. It isn't ideal, or normal, but possible.

 

[mysticplayer]

I prefer to FF before doing case prep. Going from 308 to 7mm would only need a small necking down so I don't think there will be much thickening in the neck but do check just in case.

I do FF with pistol powder and Cream of wheat/cornmeal so don't really care if the bullet fits.

After FF, I will size then neck turn and do other case prep. I feel this way my case better matches the rifles chamber,brass does get bashed while in shipment to the stores).

As long as you end up with concentric cases, either way reaches the same goal.

Jerry