Billy, as noted previously, Red Dot is a bit hot for the 20 gauge, although Hercules' reloading guides listed a few 20 gauge Red Dot loads for many years in 3/4 and 7/8 ounce payloads. Looks like Alliant dropped them all from their guide by the 2004 edition.
I'd be nervous about using Red Dot data to load Promo in 20 gauge applications without some pressure tests. I've read the statement that it is the same burn rate as Red Dot, but also note that it is denser. Don't know if that's important to the internal ballistics of the load, but that seems to be a variable to consider. There may be a good reasons that the Alliant folks only list Promo as a 12 and 16 gauge powder.
Red Dot 20 gauge pressures crowd the upper end of SAAMI specifications. There isn't much margin for error at the top of the pressure curve.
That said, I do have a favorite Red Dot 20 gauge load from the recent Hercules guides. One advantage of fast burning powders is a slight, but noticeable reduction in muzzle blast. Especially in short-barrelled quail guns.
7/8 oz lead
2 3/4" Remington RXP hull
WWAA20 wad
CCI 109/209 primer
12.0 Red Dot 1155 fps/11,300 psi
There are more recipes in any of the 80's or 90's Hercules reloading guides if you can scrounge one.
Regards, Grendel
