Shotgun patterning involves shooting at large sheets of paper to determine how pellets spread across it. Some guns shoot high, low, left, or right. Some shells distribute shot poorly, leaving big holes or gaps. Chokes influence this greatly. When shooting at a target as small as a turkey's head up to 50 yards away, it's smart to pattern your gun so you KNOW you're shooting the best load possible.
Here's how to do it at minimum cost:
1. Get a large cardboard box or build a 4-foot x 4-foot or 3-foot x 3-foot frame to hold sheets of paper (newspaper offices might sell you some un-inked paper for this.)
2. Tape or draw a life-sized turkey head or neck (commercial targets are available) in the middle of the target paper/cardboard.
3. Place the target 50 yards out.
4. Choose the gun, shell, barrel, and choke you wish to test. Most turkey hunters use a full, extra-full or a turkey choke of some kind.
5. Rest gun fore-end (not barrel) on a bench or other steady surface to minimize movement/flinching. A Caldwell Lead Sled rest is great for absorbing recoil. A bag of lead bird shot against your shoulder also does wonders, but any kind of additional padding helps. So does good hearing protection.
6. Aim steadily just beneath the turkey head on-line with the neck and fire. Try not to flinch/jerk the gun.
7. Walk downrange and use a marker pen to ink each pellet hole. Note where the center of the pattern hit in relation to your aim. Many guns are a bit high. Hitting high or to either side a bit isn't a huge problem if pattern distribution is even, but if you get an extremely close shot, which means the pattern will be tight, you could miss. Note also if there are any unusual concentrations of pellets in any areas with gaps in others (poor pattern distribution.) Count total pellet hits on the turkey head and neck and write this information down. Recognize that much of this target is non-lethal, i.e. wattles, skin, beak. Pellets need to strike the bones for guaranteed effect, so figure four hits minimum, but nine or 10 are better.
8. If hits were too few, either try a different shell or choke or move the target 10 yards closer and repeat. Eventually you will learn which shell/choke gives you maximum reach.
9. To double check, fire additional rounds of your best combo to make sure they're consistently putting enough pellets on the head/neck.
10. To double-double-check, shoot from turkey field positions (sitting, standing, gun unsupported) to see if point-of-impact stays the same. Some guns shoot higher or lower when the fore-end is rested on a hard surface vs. your hands.
The author says to aim steadily just beneath the turkey head on-line with the neck and fire.
When testing, you can also try different shot sizes. If you restrict your range to 35 yards or less, No. 6 pellets give you an advantage because there are more of them in a given weight of shot. Beyond that range, No. 6 shot begins losing energy and may not penetrate sufficiently to terminate a big tom. No. 5 shot is heavier and should work well to 40- or even 50 yards, but at that range you might want No. 4 shot. Just make sure you test it for adequate pattern density. Why not use No. 2 shot? Those are great for carrying maximum energy, but they are so large that pattern density suffers. Most turkey hunters consider No. 2 and BB shot as emergency backup ammo for body shots. Should you wound a big bird with small shot and it appears to be escaping, shoot for the body with the larger pellets.
If you restrict your range to 35 yards or less, No. 6 pellets give you an advantage, according to the author.
This, then, is how most turkey hunters work: after testing and determining their best gun, barrel, choke and shell combo, they put that head shot shell in the chamber and follow it with two emergency big pellet body load shells. Some put another small-pellet head-shot load in as their second shot and just one body load as the third shot. Sometimes a turkey will jump at a missed shot, then stop and offer a second head-shot opportunity. It's a gamble either way, but at least you'll know you're shooting the optimum load with your first shot, and that should be all it takes to get the job done.