Owning several older 12 gauge SxS's that I use for pheasant hunting led me to research lower-pressure and lower-recoil handloads suitable for their Damascus barrels. While one can perhaps use factory ammo, I prefer lower pressure handloads for an extra margin of safety.
I've found that one ounce loads of #5 shot about 1,200+ f.p.s perform well out to 40 yards. Having previously used 1-1/4 oz. heavier loads in regular steel barrels, I was initially concerned that low pressure 1 oz. loads might not have enough shot (and power) for clean "in-the-air" kills. However, the 1 oz. loads have proven themselves.
Hodgdons/IMR #7625 powder has become my favorite. I load 23.5 grains of #7625 in Remington STS hulls with a Remington 209P primer,Remington TGT12 wads, and 1 oz. of #5 shot at an estimated 1,220 f.p.s. I've also been successfully using this same load in an older light-weight British boxlock SxS that weighs 6-1/2 pounds and has regular steel barrels.
When we hunt some "state-run public areas", non-toxic shot is required. I've recently begun using "NICE SHOT" from Precision Reloading for this purpose. While it is expensive at $30 per pound (not per bag), it is safe in older tightly choked shotguns, including Damascus. What is particularly interesting, is that one loads this (tungsten alloy?) shot using the same loading data as lead. No special wads or loading data are necessary. I've been using the same 12 gauge load listed above, except substituting the non-toxic "NICE SHOT" for lead. The pheasants don't seem to detect any difference, and fall just as dead.
Some people have opined that #7625 doesn't perform in real cold weather. Living in Missouri, our winters are milder than Montana or Minnesota. Thus far I haven't encountered a sub-zero hunting days that indicated any "powder problem."
The big negative on "NICE Shot" is its cost. At $30 per pound, the reload cost approximates $2.25 for each shell. While expensive, it is a tolerable cost, and probably no worse than $4 gasoline, $100 out-of-state hunting licenses, and $60 motel rooms.
If you favor older SxS's, you may find these lower-pressure loads meet your needs.
JERRY GOLDSTEIN