I'm planning to take an old side by side for spring season this year. I'm looking for what has worked best for you in 2-3/4" loads, either factory or handloads.
Look into the Winchester Rooster XR, probably in #6s. They use the same shot lock technology that the Longbeard XR turkey loads use, but in a 2-3/4" load.
If the gun can handle it……TSS. Nothing else compares and it's not even close. I would say the Winchester Long Beard XR as my second choice. But again I've only seen a few offerings in factory TSS in 2 3/4…Federal Heavyweight. Not sure if it's currently available. Might look up APEX Ammunition and Salt Creek Ammo and see what they offer in 2 3/4".
I personally wouldn't risk shooting TSS from a old side by side. I agree with others that Winchester long beard or rooster is the next best thing to TSS.