Worc

3 1/2" guns and shells cost very little oversimilar 3" guns and shells. Weight of the gun is usually a small amount as well. There are even some 3 1/2" autoloadering models that are quite a bit light than other 3" autoloaders.

The Advantage of the 3 1/2" shells is when using steel loads for waterfowling (geese mostly). It allows the shell to keep a traditional load weight while increasing the speed of the pellets. This is important for steel as it's lighter than other shot shell pellet materials. It's even more important when using the larger pellet sizes associated with geese.

The 3 1/2" steel loads pattern better than a similar 3" load. This is as long as load weights arekept in the traditional load size which would be like 1 1/4oz or 1 3/8oz. My 3 1/2" turkey loads pattern with a lesser percentage than a similar 3" load.The 3 1/2" still getts more pellets in the pattern because it starts out with more from the start.

I don't see anything that would suggest a 2 3/4" lead loads patterns poorly out of my 3 1/2" gun nor domy buddies with their 3 1/2" models. Some times the bigger chamber patterns them better thanthe shorterchamber guns and some times the shorter chambers models pattern the shorter shells better than the longer chambersed guns.

The only to know for sure if a 3 1/2"chamber would not pattern a 2 3/4" lead load as well as a 2 3/4"or 3" chamber would to be to do the following. Take several2 3/4" loads and pattern them out of a 2 3/4" chamber. Then bore the chamber to 3" and lengthen the forcing coneand pattern those same shells. Thenbore it out to 3 1/2" and lengthen the forcing cone again and pattern those same shells. Once done you would need to get another five barrels or so and repete the above process.