It can be a complicated subject, but when boiled down, it's the powder and shot that's the real reason many patterns go away, even when a large amount of shot is fired toward the target. I am speaking of a practice used today by way of the industry and handloaders alike. That practice is massively over loading shotshell loads with heavy payloads. The end result is an overbore situation.

The author with a test pattern that indicates an overbore situation. Note the areas between the wavy lines that contain no shot at all. This is the result of a 1 1/4-ounce payload being pushed into a high performance full choked barrel.

In general, the 12-gauge shotgun, being the most used gunning system around as applied to waterfowl, will make the best use of a load consisting of 11⁄8 ounces of shot. That means that the bore of this gauge is .724 inches, as married to this payload charge, will produce the very best patterns with the least amount of barrel or choke strain.

This payload will also run down range leaving the least amount of blown patterns, ragged fringe edges on the outer perimeter of the pattern, and otherwise poor pattern performance results.

During the grand old days of the eight- and 10-bore waterfowl cannons a charge of about 1 1/4-ounce was considered massive as applied to the 10-gauge wet bird gun, and 1 1/2-ounce was also a major payload even when fired form an eight-bore cannon. I don't know how many of you have ever touched off an eight-bore goose gun, but I have, and I am here to tell you that it is almost a religious experience when that powder goes off. These big guns were about powder charge as much as pellet payload. Did those old super bore sneak boat market hunters know something we don't? I tend to think so.

If many of those mammoth market duck cannons used so little shot, why have we choked the 12-bore to death with overbore charges of steel shot pellets? As I have alluded to already, it is a sales gimmick of sorts in that as the good old American way says, "Bigger is always better, and he who has the biggest load on the swamp wins."

Well, that's not the case all the time. Massive heavy charges of shot don't add up to doing much more than pounding more holes in the sky, or sending more pellets into a mud bank across the river.

Now, before the guy that gets great results from his 3 1/2-inch 10- or 12-gauge loaded to the star crimp with massive charges of steel shot that equal the weight of a deer slug gun turns on me, let me say that yes, there are exceptions to the rule. Like good patterning gun barrels, there are gun systems that do take a liking to big heavy payloads of shot.

If you own one of them my advice is don't sell it, but hunt hard and be well on the marsh for many years to come.

Sadly enough, however, the truth is that most hunters don't pattern the loads that are being taken afield, and when some of those hunters do fire a shot or two down range at paper, they quite often don't have a clue as to what they are looking at anyway.

I hunt with some dedicated duck hunters out here in the far west that I have never seen shoot a single pattern. What these guys do is ask me if the load and choke are workable for the task at hand.

The Problem
Why is there a problem with over boring a payload in the 12-gauge duck gun?

It amounts to a large mass being squeezed down to small a hole. When this takes place, the shot charge acts like the effects of water from a garden hose and sprays shot all over the place (or at least into clumps that can miss well-centered targets at very workable range limits). This can occur even when shot payloads are a small as 1 1/4-ounce. Drive even this quite standard payload down an ultra tight full choke and the end result can be major gaps in the pattern; large enough to allow a duck to fly untouched straight through.