Promo is not a great powder for what you want. It is designed as a full target load at a cheap price. Look at Extra Lite or ClayDot or American Select.

In fact just go to Alliant Powder web site and pick 12 Remington Hull, select shot charge, primer and powder, all, to see your best options. I'd go for a 1 ounce load. The lighter loads tend to have more velocity to get proper powder burning.