I regularly fireform 243 cases to 7mm-08 with excellent results,I use 10 grains of an old shotgun powder,pack the rest of the case with fine crushed cerial,compact it down then seal the case with candle wax then fire it in my rifle & I get perfectly formed cases every time.

You would have to experement initially to see how much powder to use,I started off with 5 grains but the case was only partially formed,10 grains of the powder I used works perfectly for me,also the faster burning the powder the better.

I thoroughly clean my rifle when i' m finished to get rid of anything that may be left in the bore or chamber.

It works great,the first batch of cases that I fireformed have now been fired 11 times & are still going strong.

Give it a try,you will be amazed,I was.

Alan