Which does more good in terms of lessening ammunition-related recoil: shot charge weight or velocity? A lot of shooters and shotgun writers would tell you that lowering the velocity has the most effect because “In the ‘recoil equation’ velocity is squared.” They think the “recoil equation” is E = mc2. But the E = mc2 equation is NOT a recoil equation. More correctly it is a conservation of mass and energy equation; and a form of a momentum equation. And even if it were true that E = mc2 is a valid recoil equation, the only way anyone could come to the conclusion that velocity is more important than mass is to not run the equation. If they did and they tried different examples, they would quickly realize that shot charge weight plays the most significant role in generating recoil energy, NOT velocity.
Let’s look at some examples using a correct recoil energy equation as given (if you want a quick reference) in both Alliant and Hodgdon’s reloading manuals among other sources. Let’s say that for upland bird hunting a light shotgun is desirable (because you’ve got to carry the darn thing over hill and dale), so you’ve purchased a 6½-pound 12- gauge over/under shotgun. If you go into the typical sporting goods store and ask for help in purchasing a “pheasant load” they’re going to steer you to the traditional 12-gauge 2¾-inch, 1¼-ounce lead load at about 1,330 fps. That puppy in your 6½-pound gun is going to kick you with something very close to 36 ft./lbs. of free recoil. Ain’t going to be fun.
So putting your knowledge of recoil to work, you sensibly decide to shoot a 1⅛- ounce load at 1,300 fps. In your 6½-pound shogun that will generate about 30½ ft./lbs. of free recoil. Lower the velocity to 1,200 fps and you’ll have 26½ ft./lbs. of recoil to deal with, and by lowering it to 1,145 fps you’ll have gotten the recoil down to about 24½ ft./lbs. So here we see lowering the velocity 150 fps does lower the recoil, but not by a whole bunch.
A far more productive way to reduce the recoil would be to go to a 1-ounce load in your 6½ pound gun at 1,200 fps. That will generate only 21.9 ft./lbs. of recoil. Drop it down to 7/8 ounce load at 1,200 fps and you’ll have only 15¼ ft./lbs. of recoil to deal with in your light gun. See what I mean? The mathematics clearly tell us that reducing shot charge weight has a much more significant effect on reducing recoil than does reducing velocity. While reducing the velocity 100 fps bought us about 4 ft./lbs. of reduced recoil, reducing the shot charge weight by ¼ ounce effected a reduction in actual recoil something closer to 10 ft./lbs.
Now let’s say you’re a waterfowler and in the waterfowling world the factories these days have gone nuts in providing nontoxic loads with velocity levels well above 1,400 fps. Without boring you with the details, I’ve been contracted by government and industry to do more research on the lethality of taking waterfowl and upland birds with nontoxic loads than anyone in the world. My findings clearly show that all most waterfowlers need for a killing load at most distances when waterfowl hunting is plain old simple steel shot traveling at 1,300 to 1,400 fps.
Because of the physics of balls which causes them to slow down more quickly the faster they are launched, it’s a mathematically spurious route to think or claim that you are upping the lethality of a shotshell load containing round pellets by increasing the velocity 150 or so feet per second for a given load weight over what has been traditional. By the time the pellets get beyond 40 yards that increased per-pellet velocity and energy at the muzzle has been so substantially shed, that the faster-starting round pellets are now traveling at about the same speed as the slower-starting round pellets.
So you don’t need to feel under-gunned if you’re not shooting 1,550 to 1,700 fps waterfowl loads featuring a launch velocity fully 300+ fps above traditional. But you will feel something. And that something is awesome levels of recoil because besides heavy shot charge weights there is now significantly more velocity. A quick calculation tells us that a 1¼-ounce steel load approaching 1,700 fps in even a heavy 8.7 pound waterfowl gun generates a massive 51¾ ft./lbs. of free recoil. Now if you’re an elephant you probably have enough body mass to handle that level of actual recoil without its felt recoil component bothering you much. But if you’re a typical 200 to 250 pound waterfowler, that load is going to kick the hell out of you especially if you’re a light-bodied shooter – spelled woman or young person…UNLESS. Unless you’re shooting a gas-operated autoloader with a good recoil pad, that is. Of these the best by far I have found for reducing felt recoil is the Remington Versa Max. Its unique combination of a super thick, high tech recoil pad plus unique gas-operating mechanism makes even 1,600-1,700 fps loads fairly comfortable to shoot.
But if you’re not going to shoot a gas-operated autoloader, stay away from such loads. Anything more than 1⅛-ounce of nontoxic shot above 1,450 fps is going to be a nasty recoiling piece of equipment in a fixed breech gun. And it’s not needed to kill your birds.
Good luck and may your gun not kick you.
Tom Roster is an independent ballistics consultant and author specializing in the design and testing of shotshell loads for U.S. shotshell and reloading components manufacturers. He is a court-recognized shotshell/shotgun expert witness. Tom was formerly the Ballistics Research Director at Oregon Institute of Technology and then served as a Ballistics Specialist for the Dept. of the Interior. In these capacities he designed and administered the world’s six most extensive lead versus nontoxic shot duck, goose, pheasant and dove shooting tests ever conducted. He then co-authored their peer-reviewed scientific reports. Roster spends about 100 days afield each year testing lead and nontoxic hunting and target shotshell loads, then traveling worldwide reporting on his findings to industry and wildlife professionals, hunters and shooters, and in his writings for various shotgunning magazines. Contact him in Oregon at (541) 884-2974 or firstname.lastname@example.org.