Gunsmithing neck up or size down?

[consol]

What do you think is the best way to get to a wildcat caliber from a parent case, neck up or size down.

I am looking to make a 30-8mm and a 338-8mm.

The 338-8mm is a no brainer (perfect for me), neck up the parent case, 8mm rem mag

My thoughts for the 30-8mm was to use a 7mm stw and taper expand up, but would the neck be too thin? Would I get better cases shoving a 8mm down to 7.62? I would need to ream the neck at this point though?

Let me know your thoughts.

 

[bohem]

Re: neck up or size down?

I generally try to go down a little if possible to give room to neck turn if needed and also not thin out the neck too much. I use 270 brass to make 6.5-06

A small step up from 8mm to 338 with annealed necks shouldn't have a problem though and neither would the 7mm parent case going to 30 cal. Do you have a 339 universal neck sizer to try necking before building? Measure the neck thickness after the sizing

 

[BLAWTON]

Re: neck up or size down?

The best thing for him to do if he wanted to would be to neck down after running a expander inside all of the necks then turn the necks down just enough to clean them all up them neck down to size. If your not worried about it then i would neck up it would be easier if your not lookin for that "bug hole" setup.

And there is way mor case's that you can use to do this than the 8mm. I think there is about 5 or 6 that will work for this caliber IIRC...