I can't see all the necessary proof marks on the gun. I still await the OP to confirm that its an auto-resetting safety or not.
My working theory:
1.) The gun was a live pigeon gun (A non-resetting safety and Full/Full barrels would indicate pigeon gun, a resetting safety and Full/Full choke with 2-3/4" proof marks would suggest a fowling gun)
2.) If it had 1-1/4 ounce proofs for a 2-3/4" BLACK POWDER shell, this would mean it had been proofed for the same SERVICE PRESSURE as a 2-1/2" shell.
3.) Either the OP is mistaken that the gun has 3" chambers, OR some imbecile lengthened the chambers to 3". (proof marks will tell the original design story, a proper depth gauge will measure the chambers)
The notion of going out to shoot 3" black cloud or other extraordinary modern loads whizzing along at 1400+ FPS is out of the question. IF it has black powder proofs and 2-3/4" chambers, the notion of going out to shoot 2-3/4" pheasant loads at 1400 fps is also out of the question.
In any case, no matter what the proof marks say, that gun was proofed with the stock OFF. Just because the barrels and breach can handle being fired twice each with those loads doesn't mean the stock's wrist can or should endure those pressures. The gun should be shot with a 2.5" 1-1/8 ounce lead load at 1150-1250 fps. If nitro reproven at 2.75" length, then it would be a 2-3/4" shell of 1-1/8 ounce lead at 1150-1250 I'd be recommending.
These guns are like ferraris, they deserve a special diet. The only difference is nobody buys a ferrari and then argues that they can top off the fuel with 87 octane, it requires racing fuel. Yet with fine double guns everyone is trying to figure out how to feed dog food to something deserving of steak and lobster.
My working theory:
1.) The gun was a live pigeon gun (A non-resetting safety and Full/Full barrels would indicate pigeon gun, a resetting safety and Full/Full choke with 2-3/4" proof marks would suggest a fowling gun)
2.) If it had 1-1/4 ounce proofs for a 2-3/4" BLACK POWDER shell, this would mean it had been proofed for the same SERVICE PRESSURE as a 2-1/2" shell.
3.) Either the OP is mistaken that the gun has 3" chambers, OR some imbecile lengthened the chambers to 3". (proof marks will tell the original design story, a proper depth gauge will measure the chambers)
The notion of going out to shoot 3" black cloud or other extraordinary modern loads whizzing along at 1400+ FPS is out of the question. IF it has black powder proofs and 2-3/4" chambers, the notion of going out to shoot 2-3/4" pheasant loads at 1400 fps is also out of the question.
In any case, no matter what the proof marks say, that gun was proofed with the stock OFF. Just because the barrels and breach can handle being fired twice each with those loads doesn't mean the stock's wrist can or should endure those pressures. The gun should be shot with a 2.5" 1-1/8 ounce lead load at 1150-1250 fps. If nitro reproven at 2.75" length, then it would be a 2-3/4" shell of 1-1/8 ounce lead at 1150-1250 I'd be recommending.
These guns are like ferraris, they deserve a special diet. The only difference is nobody buys a ferrari and then argues that they can top off the fuel with 87 octane, it requires racing fuel. Yet with fine double guns everyone is trying to figure out how to feed dog food to something deserving of steak and lobster.