Forming 7mm Dakota brass

[longarm]

Has anyone formed 7mm Dakota brass from 300 RUM? Although case forming dies making 7mm Dakota brass from 404 Jeffrey are available and very expensive, the diameter of the 300 RUM cases is slightly more than the 7mm Dakota cases (even though they are both based on the 404 Jeffrey case) and Redding advise Not to try and form 7mm Dakota brass from 300 RUM as I may crack the sizing die.

I can no longer buy 7mm Dakota brass as I live in Australia and US export restrictions mean that I can't order the Dakota brass. I have about 120 cases left. So I am wanting to make the brass. I have a few hundred 300 RUM cases.

 

[Lefty7mmstw]

Has anyone formed 7mm Dakota brass from 300 RUM? Although case forming dies making 7mm Dakota brass from 404 Jeffrey are available and very expensive, the diameter of the 300 RUM cases is slightly more than the 7mm Dakota cases (even though they are both based on the 404 Jeffrey case) and Redding advise Not to try and form 7mm Dakota brass from 300 RUM as I may crack the sizing die.

I can no longer buy 7mm Dakota brass as I live in Australia and US export restrictions mean that I can't order the Dakota brass. I have about 120 cases left. So I am wanting to make the brass. I have a few hundred 300 RUM cases.

You likely will crack the sizing die on that one. I cracked the sizing die twice with a 7 rum that was chambered slightly over max. dimension (less than .010") so I think they're pretty much correct that you shouldn't go there.
What I'd do is shoot what you've got up and re-chamber or re-barrel to a caliber you can get/make where you are when your stuff is used up.