What are the important factors forming brass with a new barrel? To me it is slow rate of fire to keep the heat to a minimum. Anything else? What powder produces the least heat and wear and tear on the barrel? Thoughts?
Many times fireforming loads shoot as well as formed loads. I regularly form 22-250 to 6XC in matches with the same loads I use after they are formed.
4 ) Fireforming bulletless / fillerless / wadless / plugless. Just a pistol primer and Bullseye powder, about 20% of case capacity.You have two choices:
1) Direct Fire-forming using live ammo: Pros - Quick & easy and the fire-forming rounds are very accurate; Cons - Use up barrel life and reloading component costs
2) Cornmeal / Cream of Wheat (80% Fire-form): Pros - no wear to the barrel and no wasted reloading components; Cons - time consuming
3) Alternatives: Hydro forming or Use a donor gun to sacrifice the barrel life
You didn't mention what caliber so this may also play into the decision if it requires multiple steps to form the cartridge. Things to also consider is the (1) number of cases that you want to form and (2) caliber that you are forming (barrel life consideration). If you wanted to form 500 cases of 223AI then you are talking about 1/10 of its barrel life... not that big of a concern especially since the .223 rounds used for fire-forming will still be very accurate. If you were talking about 6PPC/BR or some other caliber with a 1,000 round barrel life then you might want to go with either the Cornmeal/Cream of Wheat Method to save barrel life. Either method can work well. Aside from barrel life, the choice is simply a trade-off between time or money.