12 Gauge vs 20 Gauge for Duck Hunting

The verdict

Buy a 12 gauge unless you have a specific reason not to, and if you do have that reason, buy the 20 with confidence. The 12 throws roughly a fifth more shot in the same shell length, has vastly more loads on the shelf, and is the only choice if you also hunt geese in fields. The 20 gauge kills decoying ducks cleanly with the right load, weighs less to carry, and kicks noticeably less — and for a smaller-framed shooter, a young hunter, or anyone who flinches with a 12, the gun they shoot well beats the gun with the bigger number every time.

What the 20 is not is a long-range gun for big birds. If your hunting is pass-shooting divers on big water or geese in a cut field, the payload gap becomes a cripple-rate problem rather than a preference. Inside decoying range over a spread, it simply is not.

What the published payloads say

The gap is real and it is measurable. In HEVI-Shot's HEVI-Metal Xtreme, the published 12-gauge 3-inch load carries 1 1/4 ounces at 1,450 fps and the 20-gauge 3-inch load carries 1 1/16 ounces at 1,350 fps, from the same line, in the same shell length, with the same wad. That is about 15 percent less shot, moving 100 fps slower. Kent's Fasteel line tells the same story: the 12-gauge 3-inch Fasteel 2.0 is published at 1 1/8 ounces while the 20-gauge 3-inch Fasteel+ is published at 1 ounce.

Fewer ounces means fewer pellets, and fewer pellets means a thinner pattern at any given range. That is the entire ballistic argument, and dressing it up any further is dishonest: a 20 gauge pattern runs out of density sooner than a 12 gauge pattern of the same shot size. Where it stops mattering is inside about 35 yards, which is where a decoyed mallard is when you should be shooting anyway.

The 20 gauge has one genuine equaliser, and it is dense shot. Bismuth at about 9.6 g/cc and tungsten at a published 12 g/cc let a smaller payload hit with the energy of a bigger one, which is exactly why tungsten-blend loads in 20 gauge have changed how seriously people take the gauge. It is also why the cheapest way to make a 20 gauge work on ducks is the most expensive shell on the shelf.

Load availability is the real gap

Ballistics are only half of it. Walk into any store in a flyway town in November and count the boxes: the 12 gauge occupies most of the shelf, in every shot size from T down, in 2 3/4, 3 and 3 1/2 inch, from four or five brands. The 20 gauge gets a fraction of that. Federal's Speed-Shok line publishes 12-gauge loadings in sizes from T and BB down; the 20-gauge offering is far narrower, and the same pattern holds across every brand on our goose load roundup. HEVI-Metal Xtreme is offered in both gauges, and it is the exception rather than the rule.

That matters in two practical ways. First, if you need a specific shot size for the birds you are hunting, the 12 will have it and the 20 may not. Second, when you are travelling or hunting a new state and buying shells locally, the 12 is always there. A gun you cannot feed is a bad gun, whatever it patterns like.

Both gauges shoot the same approved non-toxic materials: the U.S. Fish and Wildlife Service's non-toxic shot rules apply identically, and lead is illegal for waterfowl in either gauge.

Recoil, weight and fit

A 20 gauge gun is usually a pound lighter than the 12 gauge version of the same model, and it throws less shot, so it kicks less at both ends of the equation. For a hunter who flinches, that is not a minor comfort issue: a flinch costs more birds than a payload difference ever will. It is also why the 20 is the right first gun for most young hunters, and why plenty of experienced hunters carry one on long walk-in hunts where weight matters all day and shots are close.

Fit matters more than gauge in either case. A gun that puts your eye on the rib in a heavy coat will outshoot a gun that does not, regardless of the number stamped on the barrel. Several of the guns in best duck hunting shotguns publish real stock adjustment, and a couple publish compact stocks with a 13-inch length of pull, which is usually a better answer for a smaller shooter than dropping to a 20 gauge with a full-size stock.

Who should actually shoot a 20

Shoot a 20 gauge if: you hunt ducks over decoys inside about 35 yards; you are recoil sensitive or teaching someone who is; you walk long distances to small water and every pound counts; or you are willing to buy bismuth or tungsten-blend loads to close the density gap.

Shoot a 12 gauge if: you hunt geese as well as ducks; you pass-shoot divers or hunt big open water; you want the widest choice of shells at the lowest price; or you only own one shotgun and it has to do everything. That last case covers most hunters, which is why most duck guns are 12 gauges and why our full shotgun roundup is mostly 12 gauges — not because the 20 cannot kill ducks, but because the 12 can also kill geese.

If the budget is what is driving the question rather than the gauge, start with the pump guns under the four-hundred mark: a cheap 12 gauge pump plus a good spread of decoys puts more ducks on the strap than an expensive gun in either gauge.