For low pressure 12 loads I bought up a large stock of PB and 800X, both are hard to find as they are discontinued. Clays, International or Tightwad come to mind as possible powders. Alliant powders seem just a memory these days with only a few seen in scattered places. I bought 8 pounds of Unique a few weeks back but had not seen any in two years.
It comes down to what components you have available. I keep a ridiculous number of powders on hand, along with six different primers, many different wads and enough different empty hulls to fill a pickup truck completely full. And still I come up short on too many combinations. Locate what you can buy, then go to Hodgdon and Alliant online reloading guides to see what works. Also Trapshooters.com has a reloading section with a decent number of tested and verified loads for currently available powders, primers and wads. Does you no good to find the perfect load which uses Remington Primers when none are available and last seen were north of $100.00/1,000.
Also you might need to be flexible in what low pressure load you are after. 1 ounce/ 1,100-1,150 fps works for me while other might like a 7/8 ounce load for clays in the 5-6,000 psi range. Do watch many older published loads were in lup not psi and that makes a real difference.
