The Disadvantages of the 3-1/2 inch Twelve Gauge Shell

By Randy Wakeman

There are several readily understood disadvantages to a 3-1/2 inch chamber in an autoloader or pump. Here are some of them.

1) Weaker receiver. Anytime you have a larger then necessary ejection port, you weaken the receiver commensurate with the amount of additional metal removed.

2) Longer, heavier receiver. To accommodate 3-1/2 inch shells, the receiver is longer and heavier than otherwise necessary, as is the shell elevator, links, mainspring tube, etc. The shell elevator and associated springs must be heavier to move around a heavier object, the loaded shell itself. Contingent on the model, loading through the bottom of the receiver can be clumsy, finger-pinching, or a bit of both.

3) Slower cycling. It is a matter of distance: the bolt most travel rearward half of an inch farther during the ejection sequence, then must again travel and additional half of an inch forward to return to battery. It indicates a slower-cycling autoloader and a slower to shuck pump.

4) Heavier than necessary barrel. Only the 3-1/2 inch 12 gauge shell deviates substantially from SAAMI standard 12 gauge 11,500 PSI MAP pressure at 14,000 PSI MAP. With the approximately 22% rise in allowable working pressures, the barrel must necessarily be thicker and heavier to accommodate the higher working pressure. (See the list at the bottom of this article. Note the much higher pressure of 3-1/2 inch 12 gauge compared to the 10 gauge (also a 3-1/2 inch shell).

5) Recoil is far beyond what most shooters can tolerate in standard weight hunting guns. No one can do their best shooting with a shell that kicks more. Heavy recoil promotes flinching. In addition, heavy recoil can, over time damage the human body in several ways, including joint damage, eye damage and brain damage. (Each shot can cause a mini-concussion, similar to a boxer taking a clean shot.)

6) Thicker, heavier components subject to recoil. When shooting 3-1/2 inch shells, for example the common 2 ounce 1300 fps lead load, your shotgun and its stock are subjected to higher levels of stress, shock and vibration than they would be with lower recoil 2-3/4 inch, or even three inch shells. All parts of the system are punished by the additional shock and must be made heavier and stronger to accommodate the higher shock levels. The bent mainspring tubes and cracked bolt buffers that have plagued many models get far more stress from 3-1/2 inch shells.

7) Patterning of standard length shells is degraded when fired in 3-1/2 inch chambers. Folks such as Browning have published their findings that pattern percentage improvement of ten percent or so is experienced when the unfolded shell length matches the chamber length.

8) Longer shot column than standard length shells. To pack a 10 gauge Magnum shot load into a smaller diameter 12 gauge shell, the shot column becomes extraordinarily long and therefore inefficient. Short shot columns pattern better, putting more killing pellets on target.

9) A shotgun that is designed for 3-1/2 inch shells isn't as compact, responsive, or as intuitive to operate as it would be if the action was designed around standard length shells.

SAAMI Shotshell Maximum Average Pressure (MAP) in PSI

            10 gauge: 11,000

            12 gauge (except 3-1/2"): 11,500

            12 gauge 3-1/2": 14,000

            16 gauge: 11,500

            20 Gauge: 12,000

            28 gauge: 12,500

            .410 Bore 2-1/2": 12,500

            .410 Bore 3": 13,500

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Copyright 2012, 2016 by Randy Wakeman. All rights reserved.