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Join Date: Sep 2009
Location: S Central PA 5A
Re: 100 gr..257 Sierra Pro-Hunter load.
Always check a current loading manual. Having said that, if I recall 39.5 grs. of IMR 4350 w/100gr. bullet in a 257 Roberts is on the low end of the data chart for that particular powder/cartridge. For what it's worth I've used 45.0 grs. of IMR 4350 in a Roberts w/100gr. Spitzer bullet. It's close to or at max in most rifles and does the deed on PA deer quite nicely.
Personally, I'd invest in a new powder scale.
"There is no District 12"