Joe Wood makes a good point about leaving the chambers alone. There are also some great 2-1/2" shells out there from RST, New Era and Polywad. I use RSTs in a twist steel 10 gauge Baker and Polywad Vintagers in an 1877 vintage Parker with twist steel barrels. Your Trojan should be okay with them. I just bought a very nice 20 gauge Trojan and use the Polywad Vintagers. Cheers!
But the point is there is absolutely no need or benefit to use short hulls in these guns with 2 5/8" chambers. Repeated tests by Sherman Bell, Gough Thomas, Burrard, etc., have shown no danger in shooting a slightly longer hull in these guns. And Parker, L.C. Smith, and others thought it was best for the hull to open inside the forcing cone to assure a proper gas seal. That's why they recommended the longer hull to be shot in their shorter chambered guns.
Another point: I have found many of the so called 2 3/4" hulls actually are closer to 2 5/8" when fired.
Conclusion: Keep life simple and buy reasonably loaded ammunition off the local shelf. Out of respect for the age of the gun I'd avoid anything over 1 1/8 ounce, preferring 1 ounce. Stay away from hyper velocity stuff.
