The L C Smiths locking system was probably one of the best in the world, and I'd venture to say, your gun is still tight. The locking system is a rotating drum, with a tapered bolt, that bites into a lug between the barrels, which has a tapered hole in it. Even if the system is showing wear, where the locking lever would be close to center, the barrels should still be tight. The lever on one that is not worn, will stop at the right hand side, and wont reach center. If the lever is getting toward center, that can be easily fixed, by adding a spot of weld, by TIG, in the barrel lugs hole, and filing it until it closes and fits properly. I've done about three of these over 22 years.
Anyhow, 2-3/4" loads wont hurt that system, making the barrels loosen up. The only gun close to being as good, is the Greener system, that uses a sliding round tapered pin, into the barrel lug.