Waterfowl Bonus: Barrel to Bird (How Shotguns Work)

Waterfowl Bonus: Barrel to Bird (How Shotguns Work)

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Note: Game & Fish Magazines teamed up with our sister publication Wildfowl to bring readers pertinent info, stories and tactics for this waterfowl season.

Ever get tired of making great shots in front of your hunting buddies? Me neither. But think about all the things that have to go right once you pull the trigger to dust the feathers off a greenhead. Most of us haven’t thought about that enough.

A shotgun barrel has five components: the chamber, forcing cone, bore, choke forcing cone, and choke. Each is dependent on the other to produce the most efficient pattern.

The chamber is built to contain the cartridge for which it is made. Shooting shorter shells is not a problem — now. When paper cases were universal, most chambers had a step at the end that compensated for the thickness of the hull, and shorter shells often patterned poorly. A tighter chamber may help performance, but often interferes with extraction of the fired hull.

Today, many shotguns have lengthened forcing cones, the portion of the barrel immediately forward of the chamber. In the day of paper cases, the wads used were a cardboard over-shot wad, plus felt spacing wads to ensure a good crimp when shot was added.

When the Western Cartridge Company introduced Super-X in the early 1920s, they used copper-plated shot called Lubaloy.

Although plated shot has a thin layer of harder copper or nickel that allows them to flow better through the barrel, the real reason was to prevent fusing of the lead pellets from ultra-hot gasses spurting past the card and felt wads. Plastic wads solved the problem, but because of these hot gasses, shotgun makers used a short, sharply angled cone that made the transition from chamber to bore very fast.

For example, my 1942 Winchester Model 12 Heavy Duck’s forcing cone is just shy of 3/4 inches. This short cone deformed the shot.


In the summer of 1922, Idaho lawyer E. M. Sweeley and gun writer Charles Askins began experimenting with shotgun barrels provided by the A. H. Fox Company, which were specially bored by gunsmith Bert Becker. The long and short of the experiment was the discovery of the long forcing cone.

It allowed for a gentle transition from chamber to bore without damaging the pellets. Plastic shot cups have gone even farther toward protecting shot. A number of years ago, I experimented with a Browning BPS 10. Browning clung to the Sporting Arms and Ammunition Institute’s (SAAMI) — our nation’s firearms industry watchdog — guidelines for forcing-cone dimension, somewhere around 3/4 inches. I shot a series of patterns then took it to now-retired gunsmith Greg Wolf, who lengthened and polished the forcing cone. Back at the patterning board, I did not notice any dramatic enhancement in the number of pellets within the 30-inch pattern, but the evenness of the pattern was significantly improved, which translates to more lethality when you aren’t right on target.

Askins and Sweeley also discovered that by enlarging the bore, pattern density improved. This is one reason goose hunters who shoot BBs and larger cling to the 10-gauge; the wider bore provides better patterns. The nominal cylinder bore of a 12-gauge is .725 inches — Belgian-made Brownings run tighter than this — but Askins and Sweeley found that a cylinder bore of .740 dramatically improved patterns.


The duo also lengthened the fourth barrel component, the choke forcing cone. Prior to screw-in chokes there were two primary styles of choke configurations; tapered and conical-parallel. Tapered chokes were just a taper to the choke constriction. Many manufacturers used the same reamer and inserted it farther into the barrel (from the breech) to make more open chokes.

The conical parallel was the more expensive choke to manufacture because a forcing cone was tapered to the constriction, and then the constriction of the choke was parallel. Askins and Sweeley found that making the choke forcing cone longer to a full-choke constriction of .040 — nominal full choke

Screw-in choke tubes are a major advance, but did you know Sylvester Roper developed a screw-on choke for Christopher Spencer’s Model 1890 pump gun? It was a set of three rings that screwed onto the muzzle that provided three different pattern densities!

Hopefully now when you look at your shogun barrel, you will see it in a new light.

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