Relationship of PSI to recoil?


Bruce:

The 20 ga. 7/8 oz. standard shells really kick. So, I load my 20 ga. Win. AA hulls for skeet in the 3/4 oz. Claybuster WAA20 wad version with 3/4 oz. of #9 shot and it is great. I would like to load 7/8 oz. 20 ga. in Win. AA hulls for sporting Clays and shoot an over/under shotgun. Hodgon’s website lists 3 recipes for the Win. AA 20 ga. hull in 7/8 oz. recipes using the WAA20 wad:

16.5 gr. Longshot, 1200 FPS, 9800 PSI.

15.5 gr. Universal, 1200 FPS, 10,200 PSI.

14.0 gr. International, 1200 FPS, 11,800 PSI.

QUESTION: Using the same gun and chokes, what is the relation of PSI to recoil? Will the Longshot recipe at 9800 PSI kick much less than the International recipe at 11,800 PSI? And if so, a little or quite a bit less?

Thank you.

George,

I doubt very much if you will notice any difference between a low pressure load and a high pressure one. Calculated recoil is basically a computation of gun weight, ejecta weight and ejecta speed. The velocity of the gas does have a very slight impact on the calculated recoil, but not much.

I’ve run blind comparative tests using slow and fast powders with the same muzzle velocities by having different shooters shoot different shells but all with the same payloads and muzzle velocities out of the same gun. No one could tell any difference.

You might find this page helpful: http://www.omahamarian.org/trap/shotshellenergy.html

That said, this page: http://www.gunnersden.com/index.htm.shotgun-recoil.html argues that even if muzzle velocity is the same, a difference in acceleration can translate into additional recoil. Higher pressures would incur higher acceleration.

But all of the above is calculated recoil. Felt recoil is what we worry about. They are different. Example: a gas operated semi-auto is generally felt to produce less felt recoil than an O/U using the same shell and having both guns weigh the same. The difference is because the gas action slows the recoil pulse down compared to the O/U. It’s like comparing a push to a poke. The area underneath the curves is the same because the calculated recoil is the same, but the configuration of the curve is lower and wider for the gas gun and shorter and more peaky for the O/U.

Confused yet? Me too. Bottom line, I wouldn’t worry about a slight difference in gas pressure affecting the recoil that you can feel.

Best regards,
Bruce Buck
Shotgun Report’s Technoid

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