Shotgun shells all have comparable velocity
"You don't know what you're talking about when you claim a combination rifle/shotgun is better for fall turkey hunting than a full choke 32-inch barrel, 10-gauge autoloader. My 10-gauge Ithaca has no equal in the turkey woods. The big 10-gauge shell in the 32-inch barrel shoots twice as hard and far as a 12-gauge," a veteran hunter said angrily. "Who needs a two-gun outfit?"
"A good turkey hunter doesn't need a monstrous 10-gauge anymore than a home run hitter needs a 10-pound bat," shot back a younger hunter who had just purchased a used LSA-55 Ithaca 12ga/222 Turkey Gun. "I don't intend to shoot more than 40 yards, and a 12-gauge with the right ammo is plenty adequate. When I'm gobbler hunting in the spring, I call the gobbler in as close as possible, I even try to make a mental measurement of the tom's beard. He has to be close to do that. In the fall, I often see turkeys beyond shotgun range, and the 222 Remington cartridge will help put meat on the table. Those are sound reasons for buying a combination rifle/shotgun turkey outfit."
I left the scene before the argument finished, but it was plain to see that the older hunter had no time for combination outfits or any gauge smaller than the 10. His remark about the 10-gauge shooting twice as hard as a 12-gauge is simply not true. From a velocity standpoint, all gauges, even down to the .410 bore, fall into velocity readings running between 1,100 to 1,350 feet per second. I'm sure there are exceptions, and some of the new factory ammo now available may even offer more velocity. But no shotgun shell shoots twice as hard as another shell of comparable loading.
I have to take this another step. The larger the shotshelf, the more pellets it will hold. Remington's Nitro Mag Buffered Magnum Lead load in the 10-gauge Magnum 3 1/2" shell holds 2 1/4 ounces of shot and generates 1,210 fps at the muzzle. The same shell in the 12-gauge ups the velocity to 1,260 fps at the muzzle, but the shotcharge contains only 1 1/2 ounces of shot. In a 20-gauge three-inch shell, velocity is 1,185 fps with 1 1/4 ounces of shot. Not a whole lot of difference.
We tend to think of low brass field loads as being low powered. Using Remington Shur Shot field loads, a 12-gauge 23/4-inch low brass shell carries 11/8 ounces of shot and will leave the muzzle at 1,255 fps. The same shell in a 20-gauge will offer one ounce of shot and a muzzle velocity of 1,165 fps.
Don't be lulled into believing that large shotshells have higher velocities than low brass shells. In many cases, the low brass has more speed but doesn't have as large a shotcharge.
Shotgun turkey hunting is not long range, and all the talk and ballistics on long range shooting leads many young or inexperienced hunters to feel that 50- to 75-yard shots are possible with a smoothbore outfit. Common sense should tell us that all shotgunning is short range -- no more than 50 yards at the best. To find out what I mean, pattern a dozen or so shells of various brands and sizes of shot beyond 45 yards, and you'll see in a hurry that making a clean kill at much beyond 45 yards requires a good bit of luck.
Pattern diameters are about the same from all barrels the same length and choking. In other words, a 20-gauge, 28-inch full choke barrel produces roughly the same diameter pattern as does a 12- gauge, 28-inch full choke barrel. Even the big 10-gauge doesn't offer a much larger pattern than other gauges. The .410 bore is not my idea of a turkey shell, and it should be patterned at 30 yards.
The belief that long barrels shoot farther than short barrels is another myth that has survived the years. From a pure ballistic standpoint, shotgun barrel lengths beyond 25 inches offer nothing in the way of velocity. Shortly after I started small game hunting, I became acquainted with an old hunter who had an Iver Johnson 12-gauge double barrel boasting full choke in both barrels. He said the long full choke barrels reached so far out, he didn't shoot until the "rabbit was in the next county." You know, I believed implicitly that the longer a shotgun barrel, the farther it reached out. Being just a youngster, I dreamed of owning a 32-inch double like the old hunter's.
These old myths continue to confuse hunters, and they are imbedded in many hunters today. Inquiries come in asking about barrel length. Usually, the main reason for wanting a long barrel is for "reaching" out. A long barrel is easier to swing, and it offers a longer sighting plane. Basically, that's it. They do not reach out. Rabbit and grouse hunters should stay clear of long barrels.
Literally any shotgun from 20-gauge up can be used for turkey hunting. Shell selection and shot size should not be overlooked. Pattern your shotgun at various ranges up to 40 yards with regular drawn-to-scale "turkey head" patterning targets. It won't take long to find out which brand and shot size works best in your shotgun at the yardage you expect to shoot. You'll gain much more from this type of testing than just putting your faith in a large shell and a full choke barrel.