Eschmidt7286,
Even with the gun being made later with the 2 3/4" Chambers I always recommend you use the RST or Poly SpredR shells in your 16 Gauge L.C. Smith. Keep the pressure low using 1200 FPS shells and below. The gun will last many many life times. Your gun probably has M/F choked barrels and the SpredR shells will work real well in your gun, throwing real nice patterns for bird hunting and shooting Clays. Definitely have the gun checked over by a competent Master Gun Maker prior to using it. Many people have been using the Nitro 2 3/4" shells in their L.C. Smith 16 gauge guns for ever. I do not recommend it because the 2 1/2" SpredR shells will prolong your guns life indefinitely if you clean and store your gun properly. I have L.C. Smith 16 gauge guns from just about every era, when RST came out with their shells for the Classic American double guns, I started using them and sold my MEC reloader. Your gun was probably engineered for the modern 2 3/4" Nitro shells, and you will probably have no problems shooting them, if your gun was taken care of properly. Have the gun checked out and use the RST SpredR shells in her and you should be set to go.
all the best,
Pine Creek/Dave
L.C. Smith Man