RE: How would you calculate recoil on a rifle?
Why bother? I think to many guys are getting caught up in the notion of recoil. If you are concerned enough about the gun before you shoot it too the point you want a mathematical value to put on it, you probably are gonna fear it and shoot poorly with it to begin with! Weight and caliber are not the ONLY things that effect recoil. A stocks shape has MUCH more to do with how a caliber feels than does singly its weight or material of makeup. Typically the "flatter" and more plain the stock (aka ADL Rems, standard M77s and Savage centerfires) have MUCH more percieved recoil than say a highly flared and contoured stock like those on Mark Vs, Sakos etc.
Basically a "straight stick" will not shed or disappate any recoil, it all goes back into your shoulder and face when fired. With a high combed cheekpiece and slightly tapered forearm that allows you to hold onto it, the recoil is absorbed and transmitted to a larger area with such configurations. A 300WSM Weathermaster Savage will kick MUCH more than say a 300WSM Model 75 Hunter. And I am not even accounting for recoil pads, Pachmeyer Decelerator and Simms/R3 pads are MUCH more forgiving and pleasurable than the old solid Goodyear "pads" found on old Rugers and Winchesters.
Shoot the guns and let your shoulders decide before you put a figure into your head which will then tense your body with anticipation!
RA