The question of recoil has come up, oh, a few times on this forum and several times we have refered to an on line calculator for answers. I had just recently completed this simplified version for my book and posted it on another forum so I'll post it here for those adventurous souls who would like to try their own calculations.
Recoil is calculated in three aspects.
Recoil Impulse (RI), Recoil velocity (RV) and Recoil Energy (RE. For best results, in that order.
RI=(Bw*Bv) + (Pw*4400)/225190 - lbs/sec
RV=RI*32.17/Gw - ft/sec
RE=Gw*RV(squared)/64.34 - ft lbs
Bw=Bullet weight in grains.
Bv= Bullet velocity in ft/sec.
Pw=Powder weight in grains
Gw=Gun weight in pounds
4400 is the constant which represents the exit velocity of the powder gasses. (a major part of recoil, I call it the Bill Lear effect)
225190 is the acceleration of gravity (g) 32.17 ft/sec*7000(the number of grains in a pound) This constant gets it back to common units.
This will provide a close approximation of recoil. We are generally interested in Recoil Energy and Recoil velocity.
A 375 with a 300 grain bullet and 80 grains of powder which gives 2600 fps velocity in an eight pound rifle will produce about 50 ft lbs of RE and an RV of 20 fps.