Ricciardelli answered a question for me about the difference between the 6.5-284 Winchester and Norma. The Norma is 16.9thou' shorter from head to shoulder. If a rifle is chambered to just close on the go gage for the Winchester version, is the headspace going to be excessive if the Norma brass is loaded?

How does the measurement to the base of the neck/shoulder junction compare? If it is similar to the other brass I would expect that to establish the chambering depth and the top of the shoulder would then fire form normally. If it is also too short you might have a problem that will require forming a false shoulder on the base of the neck to hold things back in the right place for fire forming. Maybe a gunsmith will kick in his opinion for you.

I'm not a gunsmith but I have a friend I load for with a factory winchester 300 wby. It has .030" headspace. (according to my stoney point bushing kit). I load him a couple of grains under max and they fireform fine. I have a shim kit for under the sizing die that lets me "headspace" the die without adjusting the lock ring so I can load his stuf (once fireformed) with demensions closer to his chamber. I have another friend with a custom barrel that seems to be up in the .020" diemensions. Between the shim kit for the die and the stoney point kit none of this has been a problem. Good luck

Weatherby headspaces on the belt. Long as that is right, blowing the shoulder forward is not a problem.

6.5-284 headspaces on the shoulder and .017 is way excessive. Way to deal with that is to form from .284, adjusting dies slowly intil the case is a crush fit in the 6.5-284 chamber and then fireform. If you already have a lot of cases in the shorter version, you can run them over a 7mm expander and then size back down just as if you had started out with .284 cases.

I gave my best rifle too much headspace.
I lube the cases and fireform.
Then I 1/2 neck size with FL dies.

The extra step is a pain, but unless using factory ammo is a goal, it is never a big enough pain to put the barrel back in the lathe.