The whole thing is complicated by the term "PERCEIVED" recoil, which is a personal opinion, but obviously affected by such factors as the area and the
shape of the butt-plate (and the size of the firer?).
Over-simplifying the physics behind "recoil" - Newton's Laws of Motion applies:-
The Second Law ( F = ma) says that the force needed to move an object depends upon its MASS and the ACCELERATION given to the object, (assuming that the force is constant then the velocity achieved keeps increasing - as the gases from the propellant keeps applying a force***, whereas in something like a catapuly there is a short-lived IMPULSE) ***
very complex as the volume the gases occupy is increasing as the projectile travels down the bore.
The Third Law is "When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body " (sometimes referred to as "Action and Reaction are equal and opposite) --- hence the rearward movement of the firearm.
Combining the two it makes sense that when the 1 oz ball from a 16bore leaves the muzzle of a 150 oz gun then the rearward velocity of the gun is (about) 150th of the muzzle velocity.... so the heavier the gun the slower it slams back. (sometimes written as Mv = mV)
As for "torque" this is a twisting motion. In a rifled firearm the "ball/bullet" is trying to move straight forward (Newton's FIRST Law --- "an object either remains at rest or continues to move at a constant
velocity, unless acted upon by a
force ") but the rifling impedes it so the bullet forces the barrel in the opposite direction to the twist of the rifling.
The next paragraph
may be breaking the rules as it refers to my experiences with BL Howdah pistols --- but the same thing would be noticed with ML ones.
At one time I had a .577/20bore*** smoothbore Howdah. Firing it my hand ended up above my head -- but the back of the hand was still pointing at 3 o'clock.
*** A slightly necked down case.
I also had a 16bore rifled Howdah. Firing that my hand again moved upwards but I realised that the back of my hand was at 10 o'clock ----- the TORQUE twisting the pistol and the hand holding it.
Just to make things less serious, I must relate this story....
We all know that at Gun Shows there are allways groups "led" by a self-appointed Club Guru, who thinks that he knows everything... ... generally when someone is just about to buy a bundhook this character will interject "Oh, you don't want to buy THAT!" Grrrrrrrrrrrrr!
I just couldn't resist it at one show where I had a nice DB Howdah on the table... so I said to the Guru -- "Did you notice that this is one of the singble trigger
recoil-less Howdahs?" to which he replied, "Oh yes --- very rare.".
One of his companions asked me "How does that work"? Answer --- "The LH barrel has a RH twist and the RH barrel has a LH twist and when they go off together the recoil cancels out!"
Fred Wilkinson (well-known British author) and DeWitt Bailey were standing nearby and they almost choked with laughter... but the Guru just nodded wisely and walked away.
Best wishes to all from a locked-down UK --- I am 250 yards from the Bisley ranges where there are 108 targets up to 600yards, 50 at 1000yards (and a few up to 1200y), 27 at 100 and 9 at 200 on "Short Siberia", a sporting rifle complex with static and moving targets, three pistol ranges (50, 30 and 8 targets), a range for zeroing rifles, a shotgun layout ----- ALL CLOSED ;-(((((((
