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BigJimP · January 2, 2009, 03:12 PM

Recoil Formula from Hodgdon reloading manual :

ReCoil Energy (in Ft Lbs) =

(Bw Mv + 4700 Pw) ^ 2
___________________
64.348 X Gw

Bw Weight of Wad and shot in lbs (convert shot weight to grains then add the weight of the wad in grains and divide sum by 7000 = lbs )
Mv Muzzle velocity of load in fps ( from loading tables )
Pw Weight of powder in load - in lbs ( number of grains / 7000 )
Gw Gun Weight - used catalog specs from Browning

7000 Grains / Lb
437.5 Grains / Ounce

Shot WT Ounces Grains by Gague
1 1/8 oz = 1.125 oz 492 12 ga
1 oz = 1.0 oz 438 12 ga
7/8 oz = .875 oz 383 20 ga
3/4 oz = .750 oz 328 28 ga
1/2 oz = .500 oz 219 .410 ga

12 gauge Wad, 1 oz, typically is 33 grains
WAA12 12 ga wad is 39 gr
WAA20 20 ga wad is 30.8 gr

Recoil calculation using a Browning O/U XS Skeet model 12ga:

1 1/8 oz 18 gr clays 1200 FPS
492gr 18gr 1200 fps
XS skeet 30" barrels 7.9375 lbs Bw 0.075 lbs
Pw 0.003 lbs
Recoil 20.40 Ft Lbs Base Line

If you double the shot load ( so both barrels go off at once to 984 grains / and the 18 grains of powder to 36 grains ) you have to leave the velocity the same - because both shells develop 1200 fps - the forumula above will give you 77.16 Ft Lbs of Recoil or about 3.78 times the recoil vs one shell going off.

January 2, 2009, 03:12 PM	#17
BigJimP Senior Member Join Date: February 23, 2005 Posts: 13,195	Recoil Formula from Hodgdon reloading manual : ReCoil Energy (in Ft Lbs) = (Bw Mv + 4700 Pw) ^ 2 ___________________ 64.348 X Gw Bw Weight of Wad and shot in lbs (convert shot weight to grains then add the weight of the wad in grains and divide sum by 7000 = lbs ) Mv Muzzle velocity of load in fps ( from loading tables ) Pw Weight of powder in load - in lbs ( number of grains / 7000 ) Gw Gun Weight - used catalog specs from Browning 7000 Grains / Lb 437.5 Grains / Ounce Shot WT Ounces Grains by Gague 1 1/8 oz = 1.125 oz 492 12 ga 1 oz = 1.0 oz 438 12 ga 7/8 oz = .875 oz 383 20 ga 3/4 oz = .750 oz 328 28 ga 1/2 oz = .500 oz 219 .410 ga 12 gauge Wad, 1 oz, typically is 33 grains WAA12 12 ga wad is 39 gr WAA20 20 ga wad is 30.8 gr Recoil calculation using a Browning O/U XS Skeet model 12ga: 1 1/8 oz 18 gr clays 1200 FPS 492gr 18gr 1200 fps XS skeet 30" barrels 7.9375 lbs Bw 0.075 lbs Pw 0.003 lbs Recoil 20.40 Ft Lbs Base Line If you double the shot load ( so both barrels go off at once to 984 grains / and the 18 grains of powder to 36 grains ) you have to leave the velocity the same - because both shells develop 1200 fps - the forumula above will give you 77.16 Ft Lbs of Recoil or about 3.78 times the recoil vs one shell going off.