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I made another 100 pieces of Mashburn brass yesterday. I thought I'd post the process for those who've never done any case forming and are a bit intimidated. It's really straightforward.

The series of pictures with the COW (cream of wheat) loading are actually 7mm RUM brass that were necked down from .300 RUM, but the process is the same.



First, run .300 Winchester Magnum brass through the 7mm Mashburn Super sizing die. I found that the only real part of the case that gets any sizing is the shoulder and neck so I simply get lube on my thumb and forefinger and coat the neck and shoulder slightly before running it though the die. Lube the inside case neck too...

These are actually 7 MSM brass and their parent, the .300 WM



The little ring you see toward the neck/shoulder junction is where I stopped neck turning when the brass were originally .300 WM. After forming, I re-turned the brass to the new neck/shoulder junction and even into the shoulder a tad to eliminate any donut situation. This is the final product:






After sizing, I prime, load 20 grains of fast-burning powder (not critical. Unique, Red Dot, etc..) and fill with COW (I use coarse Polenta ) to the shoulder area...





When I did these, I filled them too full into the neck. Just shake some out to allow for the next step...


Melt some paraffin wax in a double boiler and use some sort of eye dropper to dispense it into the case to the top of the case mouth...












At this point when the wax has cured, go out and chamber shells and pull the trigger to form. The batch I just got done forming was pretty much fully formed in length anyway.







Simply decap, tumble, size and load....