Shotgun Shell Lengths

RIO Royal Star Slug

RIO Royal Star Slug

Shotgun shells are measured after the shot or slug has been discharged, so if your shotgun is chambered for 2 ¾ inch shells the shell before discharge will measure less than 2 ¾. Your shotgun will have a forcing cone that the crimped open portion of the shell will make contact with once the shot is discharged. The position of the cone is determined by the length of shell the shotgun is chambered to use.

The cone forces the shot down to the bore size and there is tremendous pressure at this point. Using longer shells than what your shotgun is chambered for will increase the pressure and can cause damage or injury. Additionally, using longer or shorter shells than what the gun is designed for can deform the shot causing you to lose accuracy and range. Using a three inch shell in a shotgun chambered for 2 ¾ means the shot is closer to the cone and will not allow the shot to expand safely and the compression can cause damage.

Your shotgun essentially has two forcing cones, the one at the breech and one at the muzzle end, which is the choke. The hot gases will push the wad down the barrel and the mass of shot will expand, so when using the shell size that your weapon is chambered for means there will be a smooth transition from the end of the hull in to the forcing cone.
For example, if you fire 2 ¾-inch shells in a chamber that is designed for a 3 ½-inch shells there will be a jump from the hull end to the forcing cone. This means the shot is unsupported during its short trip and the expansion will cause the shot to move or migrate and then the shot is not lined up properly and will become deformed as it is forced into the cone and ultimately into the reduced bore.

You can of course shoot a 2 ¾ inch shell in a shotgun designed for three-inch shells, and in this case the gap is less, which results in less deformity of the shot, and you may not even see a difference in your shot pattern. As stated earlier however, shooting longer shells in a chamber designed for shorter shells can be problematic and even dangerous in some cases.

Some shooters believe that firing shorter shells in a shotgun chambered for longer shells produces a better-shot pattern. There is really no hard and fast information concerning this and much of what has been stated is speculation and not backed up by ammunition manufactures. There is a reason weapons are chambered for specific shells so it is recommended that you only fire shells sizes for which your shotgun is chambered to fire. The length of the shell determines how much shot is in the shell.

All shell lengths fire at the same velocity so you would purchase a shotgun chambered for a specific length shell based on how much shot you want in the shell. Much comes down to personal preferences and type of game you plan to hunt.