Shotgun recoil calculator formula–
Everyone that reloads shotshells for their shotguns is always faced with the problem of wondering how much recoil will be produced in their individual shotgun from their reloaded ammunition. Here is a shotshell reloading formula that will get you close to your own pet shotshell load recoil if not exact.
1. Add the weight of your powder, shot and wad together expressed in grains.
2. Now multiply this number by the weight of the powder.
3. Now take the weight of the shotgun in pounds and decimal fraction of pounds and multiply that number by 80.
4. Now divide the number you got in step (2) by the number you got in step (3). The answer you get will be foot pounds of recoil.
This method of calculating recoil is based on the energy of the powder used and not velocity, also beings not all powders possess the same chemical kinetic energy this formula will not be 100% but it will be very close.
Also you will note that when using this formula you will find that even though you will have velocity levels the same between reloads it will reflect that there is a difference in actual recoil between them.
Simply put the law of physics says for every action there is an equal and opposite reaction. In light of that fact it is more than fair to say that all shot loads of equal weight and velocity should recoil the same. However, there is an acceleration time frame chemically engineered into all reloading powders that cannot be ignored either and that acceleration time frame equates into what a shooter feels on his shoulder or felt recoil.
Did you achieve full acceleration of shot load to peak velocity in 6″ of barrel or 26″ of barrel as this equates into the felt recoil factor. Read this article on how to pattern a shotgun, next.