Which shot size is right for small game?
There has always been heated arguments over the size of shot for various types of small game.
Starting with 8 trap shot down to the large 4 shot, hunters have some pretty strong ideas about which size to use. For the most part, 6 shot is suitable for most all types of small game shooting. When I was growing up in French's Corners, some of the veteran small game hunters used nothing but 4 shot in supposedly high velocity shells. Since these hunters were well skilled in shooting, they had good results most of the time. But 4 shot is not the best size to use for general hunting.
As the shot charge exits the muzzle, it begins to string out and also expand in diameter. The expansion is called a pattern that is basically governed in size by the choke constriction in the barrel. The tighter the choke, the smaller the diameter of the pattern. In reality, it is not the size of the shot that kills, it's really the density of the pattern. The thicker the pattern, the more shot will hit the animal. Since every pellet that strikes the target contributes to the kill, it's essential to have a large number of pellets in the pattern.
There are considerably more pellets in an ounce of 8 shot than in 4 shot. Since the patterns for both shots will be the same diameter when fired from the same barrel, it obvious that the 8 shot will produce a much thicker pattern, But you say the heavier 8 shot will penetrate deeper than lighter shot. While there's some truth to that, the fact remains that at normal shooting distance up to 30 yards (most rabbits and grouse are taken at distances below 30 yards), small shot will reach the vital areas.
I'm on pretty safe ground in saying that many small game hunters do not pattern their shotgun. They simply assume it will hit where it is pointed. To some extent, that is true, but don't count on it. You might find that your particular shotgun prints its pattern a full six inches or more from the aiming point. Most of the time, the pattern forms high or low, and this has to do with the pitch of the stock. The pitch of the stock (whether it shoots high or low) is determined by the angle of the butt plate on the end of the stock. Changing the angle a few degrees will raise or lower the impact point of the shot charge.
Since pitch is somewhat a mystery to most of us shotgun fans, it's best to use the services of a gunsmith. However, placing thin shims under the toe or heel of the butt plate may show which way the angle should be changed. Then, a gunsmith can cut the pitch angle properly.
The best way to pattern a shotgun on the home level is to fire at sheets of newspaper. The first shots should be fired from a solid rest with the shooter actually aiming the shotgun much like a rifle. A good rest is a folding ironing board. It will become apparent after four or five shots just where the gun is impacting on the paper. Even though the pattern is not forming on the bulls-eye on the newspaper, don't panic. Shoot four or five more shots from the off hand position, not using a rest. If the pattern forms in the same area as when fired from a solid rest, it is fair to assume the shotgun will need the services of a gunsmith. It's also a good idea to shoot a few rounds by tossing the gun to the shoulder and firing quickly at the bulls-eye. This is pretty much what you would do in the field. It's a learning experience.
Sometimes, two-barrel shotguns will not pattern to the same point with both barrels. One barrel may shoot a little to the left while the other barrel goes low. This problem is normally found in inexpensive doubles . It can be cured, but it might not be worth the expense.
Finally, we come face to face with choke. It was a solid belief some years back that the more choke the better. A tight choke allowed the hunter to "reach out." Single shot scatterguns were normally choke "full." The truth is too much choke is worse than too little. A good compromise if "modified" choking, but small game hunters using "improved cylinder" will be more successful. That my be hard to believe, but it's true.