Never Let Your LeftHand Know….
Q:I was interested to read your comments about right vs lefthand twistin rifling. There is no ballistic advantage of one over the other;the Coriolis effect is zero over normal shooting ranges. Newton’sthird law of motion (the action/reaction one) gets a fair workoutwhen any gun/rifle is fired. One thing I have never seen mentioned isthe torque reaction imparted on the rifle by the rotation of theprojectile created by the rifling twist. This force is proportionalto the square of the angular velocity, which is considerable. Aprojectile traveling at say 3000fps in a barrel with a 1:10″righthand twist is rotating 3600 times a second clockwise. The torquereaction kicks the stock anticlockwise (to the left) into a righthandshooter’s cheekbone which can be painful after a number of shots. Ireckon a rifle manufacturer would have a marketing advantage if theynegated this by putting a barrel with a lefthand twist on arighthanded rifle and a barrel with a righthand twist on a lefthandedrifle. The cost would be negligible and felt recoil would certainlybe reduced. What do you think?
A:Afraid I’ve never had the experience of having the stock kickedanti-clockwise with enough force to bruise my cheekbone, and I’veshot some powerful rifles in my time. However, on a few occasionswhen shooting real ultralight rifles, I’ve had the rifle actually tryto twist itself out of my hands. This was most pronounced with alight rifle which had a titanium receiver. This torque is probablycaused by a twisting or rotating tendency created by force beingapplied to the receiver. Torque is calculated by the multiplicationof the force and the shortest perpendicular distance of the force. Asyou mentioned, energy from rotary motion is equal to torque timesangular displacement. The torque twist is an opposite reaction to therifling in the barrel which is forcing the bullet to turn one way asit turns the gun the opposite way. It is normally experienced in bigmagnum handguns and lightweight rifles firing high velocitycartridges. And indeed, it would be correct to say that it wasNewton’s third law of motion in operation once again. Puttingdifferent twist barrels on right and lefthanded rifles would notreduce recoil to any noticeable extent. It would add to the cost asit would require tooling up for two different rifling methods. Ican’t see any commercial riflemaker being bothered to do that. In anycase, why bother?