The S&B shells (along with Wolf and Nobel, to name others), use roll crimping to seal the shell. They roll the lip of the shell onto a piece of plastic or cardboard to cap the shell. This is a cheaper way, and is used on cheaper imported buckshot.
Domstic buckshot(Win., Rem., Fed., Estate) uses star crimping. This process neatly folds the plastic on the hull onto the top of the payload, sealing it off. It takes a little more work, so it costs a litlle more. It also results in a shorter finished length, allowing maximum magazine capacity.
The important thing to remeber, these are both 2 3/4" shells. The 2 3/4 inch designation refers to the shells length after being fired. Take a fired hull of some domestic star crimp ammo and an empty roll crimped import buckshot hull. You will notice that they are exactly the same lenght, and if you measure you will find they are both 2 3/4 in. long.
Shotshell length designations refer to the length of the shell AFTER being fired. Before being fired, domestic buck is sbout 2 3/8 in long. Wolf (roll crimped) is about 2 5/8 in long before being fired