Ithaca SxS
I have my grandfather's Ithaca, not sure the exact model name, I think it is a New Industry Double. I do know that he bought it in 1909. You can still see the setter or pointer (I don't know dogs) engraved on the sides. 12 ga, 26in barrels.
I am curious why you want to deactivate the automatic safety. Is it just because it bugs you? Or does it interfere with the gun's function?
My grandfather's gun was made to his order (he said), buttstock to his specs, it has a bit more drop than is common, and is choked full/full. Double triggers, "fluid steel" barrels, and a splinter forend. It also has a 3 position safety.
SAFE (center), you can see the letter "S" through a hole in the safety slide piece, OFF (forward - safety goes ON when actioned is opened), and a third position, at the rear. In this position the safety is off, and does not go on when the action is opened.
Also, with the safety in the rear position, if you pull and hold the triggers with the action open, holding the triggers while you close the action leaves the gun uncocked (hammers down). This was the way my grandfather showed me to store the gun. You NEVER have to snap the hammers (or buy snap caps).
I have only been able to look at a few Ithaca doubles from the pre WWII era, and none has had a safety set up like this.
He also told me that the springs were guaranteed never to take a "set". He wrote Ithaca (in 1949) and asked if the guarantee was still good. They wrote back tha it was. I have the letter. The VP at the time added a note to the bottom of the letter, saying that using the "Express" loads might not be a good idea in the long run. ANd he went on to say they were not needed, as they were "akin to using a bulldozer to thread a needle".
I take this to mean not to use the 3 3/4 dram loads often, and that the 3 1/4 dram loads are fine. Your gun is newer, and likely has better steel in the barrels, so it may be ok for the heavier loading, but why risk a fine old gun? There is no need.
And that is where I would stand on dis-assembling the lockwork. remove the buttstock and you can get out all the crud that's coming out with soaking and /or spray cleaners. If it ain't broke.....
And, no matter what else you do, DO NOT EVER SHOOT STEEL SHOT through that gun!!!!!!
A worst case would be the gun blowing up. A more likely case would be just blowing the choke out/splitting the ends of the barrels.
Because of the way choke is measured (% of pellets in 30inch circle @ 40 yds), the actual amount of constriction in the bores can vary alot. Guns choked in the era of paper shotshells and card/fiber wads have a lot more constriction in the bore for a given choke than guns made after the introduction of plastic shotshells and their plastic shot columns and cups.
My Grandfathers rule of thumb was for a 12ga, a full choke gun would balance a dime in the muzzle (dime would not fall through). Take any full choke gun made in the last 50 years, and a dime will drop straight down the barrel! Firing modern shotshells in these old guns actually results in what would be (by todays standards) an "extra full" or "super full" choke. Which is another reason to stick to the lighter field loads, to reduce the strain on the gun.
Shooting steel (soft iron) shot through one of these guns can create a VERY DANGEROUS situation, because steel shot will not compress (to get through the choke) anywhere near the amount lead will. And that creates dangerous pressure levels where the metal is very thin. DON"T DO IT!
Sorry for the shouting, you likely already know about the dangers of steel shot and old shotguns, but on the off chance you didn't, I felt it had to be said.
Does your gun have ejectors? Or just extractors? My Grandpa guns has extractors. He told me once that "If I knew then what I know now I would have spent the extra money and gotten ejectors". I think it he said it was about $2.
I no longer recall clearly what he said he paid for the gun, new, stocked and choked to his order, but I think it was around $17. About a week's wages for a middle class tradesman in those days.
There are many more costly guns, and some finer. Fox, Purdy, Parker, etc. may mean alot to other folks, but not to me. For me, it will always be Ithaca, and one Ithaca in particular. It may not be worth a lot of money but it is rich in memories and family history. That gun will never be sold. EVER!
Forgot, the gun is a western arms (long range)/Ithaca made about 1932-33. and is there any place we can get a diagram