Thank you very much Mr Books, and everyone who commented. I will be hammering out this falls ammo shortly.
It's always easy to find A mix for a modern shotgun using components that are easily available, however a vintage shotgun with Damascus barrels is a different story.

Our Canada's run beteen 9 to 13 pound on average. Period correct loads in composite barrel guns are low velocity. My experience and observation has been #2 bismuth just doesn't get the job done, #1's and bigger are better as they have more mass and can penetrate to the vitals. #4 bismuth seems to work better than it should. Plenty of times I have been loaded with #4 for duck and a goose or geese suddenly appear with no time to change loads. I think they work because the #4 shot with more pellets has a better chance of striking the head and neck. If I was hunting the monsters you have I would go straight to bismuth BB in 1 3/8 ounce. There is a loading for it using Longshot that is sub 9000 psi with a fold crimp.

This forum has the best advise available on 2 7/8 inch 10 G loading. Tested loads actual experience.

William

Paul Harm- the shotgun primers sold as BP primers are a colder primer. Apparently modern BP rifles provide better accuracy with a lower brisance primer.

I didn't know they were a colder primer - I've always been told just the opposite, that BP primers were hotter to get the powder to go off. I've also been told they're just shotgun primers in a different package. Anyways we're not shooting rifles looking for a one hole group, but shotguns we just first want to fire a shell. If it were me, I'd go with the hottest primer I could find, like a federal 209A. JMHO. Good luck.

13 year ago data, but still good today I would assume

http://www.armbrust.acf2.org/primersubs.htm

On another note I was just rereading my old DGJs, and in one, Sherman Bells I believe #12, about " Finding Out For Myself, where he tested Green Dot and BP. He did it so both loads had the same velocity, around 1225fps. They both had almost the same pressure - with in a 100 psi. He tested 1, 3, 6, 9, and 12"s down the barrel. It was the same at each distance. Here's the cool part. He made a magnum load with the BD, I don't remember exactly, but about a 1 3/8oz at 1400fps, if memory serves me correctly. Anyways, it was 10,000psi 1" out, but it very quickly went down to the light loads . I think at 3" out it was only 4000psi. He said he couldn't explain it, just reporting what he found. So if you're going to load BD at data that gives you 1200fps at a 1 1/8oz or so you'd be perfectly safe. He claimed [ in a different article that used BD for a different experiment ] that it seems like it was designed to replace BP. Just something to think about.

The load table from the Parker Story that Garth posted is in my opinion the correct approach and as a maximum service load and proof load is appropriate for a Parker shotgun with either composite or fluid steel barrels in as new condition. If barrels or chambers are honed thin or otherwise infirm then of course the situation is different.

If the stock is not in good shape then recoil should be reduced also unless those problems are corrected .

I agree with Bruce, but the only problem is many of the powders aren't produced anymore. I've always went by the thought that if it's a mild load in a 12ga, it's going to be less in a 10ga, even with a different wad and hull. All 10ga hulls are straight walled, so with mild loads I treat them all the same. JMHO, but pressures aren't going to change more that a couple of hundred psi if there's a slight difference in hulls. In the Alliant handbook, the same green Dot load in both the Federal and Remington hull have the same pressure. Should tell you something. I think a 10ga 1oz load is about as good as it gets. The shot column is so short there's way less shot deformation, and the shot string is shorter, so there's more shot at any given time in the pattern. Just use a 12ga 1oz load data. Did I say no recoil ? If one just has to go to those 1 1/4 or 1 5/8 oz loads the Alliant handbook shows Unique and Greed Dot with 7500 to 8800psi loads that should be good for our old SxSs. These are with our modern hulls that can be bought from BPI or Precision Reloading. We can use the old load data, but how many of us have those older hulls? All I have are the more modern Rem, Fed, and Win hulls. And they pretty much all look the same, and with slight adjustment can be all loaded the same. Oh, there's some slight differences in how high the base wad is, but that's only going to make a difference in total load height. That will make a difference is final crimp. I only shoot clay targets, with 1oz shells at lower pressures, so I sometimes forget some of you guys like more payload so your pressures could be quite a bit higher. I think if it's going to be a light load, then 12ga loads will work just fine. If heaver, then those two Alliant loads with those two powders will work. JMHO. Someone please pipe in if you find fault with what I said. Different opinions are always good.