Dixie,
I have noticed that there isn't any difference in velocity between 2-3/4 inch and 3 inch slugs in the several major ammo factory sites.  I assume that with a given projectile weight, and a maximum pressure limit, that there is enough space for all the powder  needed in a 2-3/4" shell.  If that is true, why are there any 3 inch slugs being made at all?  Is it to satisfy the customer who thinks bigger is better?  What is your opinion of getting a rifled choke tube for my Browning Gold vs. buying a fully rifled barrel for slugs.  I have noticed that some manufacturers are producing 12 gauge slug loads with velocities around 1900 fps.  I assume that the projectile is lighter than the normal 1 ounce slug to get that velocity.  What is your opinion of these slug loads?