Bill is right. 2 3/4 would be correct for multiple gauges, which are not stated if I follow correctly.

No where in this thread has the gauge of the gun in question been mentioned. In 1904, a Parker Bros. gun could have been ordered for any length shells our U.S. ammunition manufacturers offered -- 12-gauge 2 5/8-, 2 3/4-, 2 7/8-, 3- or 3 1/4-inch shells; a 16-gauge for 2 9/16-, 2 3/4-, 2 7/8- or 3-inch; a 20-gauge for 2 1/2-, 2 3/4-, 2 7/8- or 3-inch; and a 28-gauge for 2 1/2- or 2 7/8-inch shells. Generally speaking, Parked Bros. held their chambers 1/8-inch shorter than the intended shells.

It’s 1904 DH , with 30 inch barrels , say titanic steel on the rib , is a 12 gauge

Here is a letter on my DH made in 1896 with the owner ordering 2 3/4” chambered barrels.

The heaviest 12-gauge loads our North American ammunition companies offered in 1904 were 3 1/2-drams of bulk smokeless powder or 28-grains of dense smokeless powder (such as Infallible or Ballistite) pushing 1 1/4 ounce of shot. Such loads could be had in the 12-gauge 2 3/4-inch or longer cases. In those days the longer shells had more/better wadding, which many shooters believed an advantage, not heavier pay loads. The pressure of those loads was a bit higher that modern day SAAMI specs. When progressive burning smokeless powder, high velocity loads (Western Super-X, Peter High-Velocity, Remington Nitro Express, etc.), came out circa 1922, they moved out that 12-gauge 1 1/4-ounce load at higher velocity but actually lower pressure than the old bulk or dense smokeless powders. That did subject stock heads and bolting to greater recoil forces.

While no one can tell you over the internet what ammunition may or may not be suitable in a given gun, I'd bet the chambers in the 1904 gun are at least 2 5/8-inches which is perfectly suitable for 2 3/4-inch shells.

Thank you all for the advice , I’m buying it and going to have it double checked out befor I put some shell through it , I’ll get the chokes checked and try light 1 ounce loads first ,
I’ll post some pictures as soon as I figure out how to
Thanks

My 1898 DH 12 has 30” Titanic barrels with 2 9/16” chambers and I often shoot 2 3/4” AA’s at trap and SC.






.

i shoot mostly 2 1/2 RST from my 1904 VH but have shot modern 2 3/4 on occasion. pretty sure they are the original chambers. BTW...if you check the RST website often....they do become available but you can't hesitate.

Phil, that is one interesting letter. A DH with Vulcan Steel barrels, and a no safety pigeon gun to boot. The buyer's name has a familiar ring to it. Is he a competition shooter?