Powder Rate And Recoil


Dear Technoid,

I was wondering if you think that powder burn rates effect recoil greatly, or at all. I have tried switching from red dot to titewad and i was wondering if its possible to feel a recoil difference. I am trying to minimize recoil in my 12 gauge target loads, and my first step was less powder, second step was going from 1 1/8 oz loads to 7/8 oz loads, third will be trying to increase the weight of the gun.

And after you answer my question may change powders. Cant wait to hear the scoop…………….. thanks

S

Dear S,

The first thing that I have to mention is that recoil is a surprisingly subjective think. It is easy to measure mathematical “free recoil” using the formula. It is basically a function of gun weight, ejecta weight and ejecta velocity.

But… us human beans aren’t mathematical formulae. Different people sense recoil differently. It really gets personal. And I don’t mean gunfit induced face slap… I mean true recoil, the kind that comes through the shoulder and up through the spine in the back of the neck to the head. If your gun kicks you in the face, you have a gun fit problem, not necessarily a recoil problem. It’s the same pain, but a different cause.

When I was shooting International Skeet a million years ago, the Russians had set all sorts of records using some pretty heavy 32 gram shells, legal at that time. A bunch of us got together to experiment to see if higher velocity would help. We also experimented with different burn rate powders to see if we could lower the recoil and muzzle jump produced by these hotter shells.

The theory has always been that slow burning powders give more of a push than a jab when compared to faster burning powders producing the same velocity. I remember that we came up with two loads producing the same muzzle velocity, one of which used DuPont’s fast burning 700X and the other which used seven grains more of the very much slower SR 7625. That was 35% more powder to achieve the same velocity, so it really did seem that we were comparing a slow powder and a fast one.

We did a blind test and didn’t let the shooters see which shells we were putting in their guns. At the end of the test, three of the six shooters felt that the 700X was softest and three felt that the SR 7625 was softest. As I said, it is subjective.

Mathematically, the 700X wins. The free recoil formula counts the grain weight of the powder charge in with the ejecta weight, so the more grains of powder you use, the greater the ejecta weight and the more free recoil. Obviously, seven extra grains of weight in an eject weight of over grains doesn’t amount to much, but the mathematics are on the side of the fast powder.

The bottom line is that whatever difference powder selection makes, it won’t be much. Lowering ejecta weight by going from 1-1/8 oz to 7/8 oz at the same velocity will make a HUGE difference. As a rough rule of thumb, lowering eject weight or lowering eject speed will lower free recoil by 2:1., i.e. a 10% reduction in ejecta weight will lower recoil 20%. It isn’t an exact ratio, but it is in the ball park. Reducing shot from 1-1/8 oz to 7/8 oz and leaving muzzle velocity the same will cut mathematical free recoil by a whopping 35%. Going form 1-1/8 to one ounce cuts it 19%.

Adding weight to your gun cuts calculated free recoil on about a 1:1 ratio. Raising the weight of your 8# gun 10% to 8.8# will cut recoil (using a 1-1/8 oz load at 1200 fps) from 17.63 ft/lb to 16.03 ft/lb, a drop of 9%.

In my experience, by far the best way to tinker with reducing recoil is to fool around with the shells. Even just picking a 2-3/4 1145 fps load vs the same weight in a 3 dram 1200 fps load will reduce recoil 9% without the slightest loss in real world performance.

I do think that you will notice a fall off in scores if you go from 1-1/8 oz to 7/8 oz, but many people seem quite content to go to one ounce. A one ounce load at 1145 fps has 26% less recoil than a 1-1/8 oz shell at 1200 fps.

OK, since you didn’t ask- what do I do? I got tired of being kicked to death by heavy loads in my O/Us so, rather than give up any shell performance, I switched to a gas gun for serious competition work. Now I can have my cake and eat it too. The vast majority of shooters, almost all of whom are better than I am it seems, take the other approach and stick with their O/Us, but use lighter shells. Either way, there is no need to suffer. Life is just too short to get pounded into the ground like a tent stake.

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error, never in doubt.)

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2 Responses to Powder Rate And Recoil

  1. Bill E. says:

    It would seem that instead of slower, the fastest powder which would result in the velocity wanted, but requiring less amount would reduce recoil. You have effectively reduced the ejecta by the lesser amount of powder so wouldn’t you have dropped recoil by that very small amount?

    Like

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