Left-hand twist and barrel torque

[NukeMMC]

So in reading and watching a bunch of posts about left-hand twist barrels, one common trait is touted about them in that with bullet rotation counter-clockwise, when looking from breech-to-muzzle, those bullets tend to impart a similar-direction torque to the barrel, rotating the cheekpiece (on a right-handed shooter) into the shooter's cheek, arresting the rifle movement.

For the bullets to be moved in the counterclockwise (CCW) direction when looking from the base, wouldn't the barrel be moved in the clockwise (CW) direction. Newton's 3rd Law should apply and the equal & opposite force of the bullet spinning CCW would be the barrel torque to be in the CW direction.

To me, it seems moot, as in the 40+ years I have been shooting competitively, 30 with centerfire rifles, I have never noticed rotation of the rifle I was shooting. Is this something anyone has really noticed?

 

[AIAW]

Think of it from the rear of the rifle looking down the bore. A friction-force (the bullet) rotating CCW will tend to force the cylinder (barrel) to also rotate CCW ("sliding" friction). For a right-handed shooter, this can be beneficial (not accounting for the Coriolis/Spin Drift/Northern Hemisphere vs Southern Hemisphere attributes).

The opposing force is the rotation itself, coupled with heat of the land-to-bullet-bearing surface friction (of course the heat is not felt as "recoil").

 

[NukeMMC]

The bullet is not spinning in the bore until the rifling actually forces the bullet to rotate. The bullet cannot impart CCW rotation onto the barrel ... quite the opposite, in fact, the barrel imparts the rotation onto the bullet.

 

[AIAW]

Hmm, I guess you have a point there. I'd have to put my physics hat on and think about that piece for a bit.

 

[spife7980]

The bullet is not spinning in the bore until the rifling actually forces the bullet to rotate. The bullet cannot impart CCW rotation onto the barrel ... quite the opposite, in fact, the barrel imparts the rotation onto the bullet.

True but the bullet is also pushing forward, pushing on that angled land surface will still impart a force acting on the barrel, and on that angled spinning surface it will torque the barrel around a tad.

 

[Steel head]

Shooting bigger bullets(200+) you really start to notice it but I definitely feel it in compromised positions as well with my 260.

If your bipod or position is crap rifle will noticeably rotate.

The plus I see is the left hand twist barrel for a right handed shooter is the cheek piece and grip will try to rotate into cheek and grip hand instead of away from it.

 

[Rust]

Equal and opposite reaction. If you are accelerating and forcing the bullet to spin at 180,000 rpm or so, the same amount of force is imparted in the opposite direction to the barrel/rifle. Not too noticeable in a .223 or .308, but definitely noticeable with my .338 or .416. Open the hood to your car, rev the engine, watch the motor torque to one side, the opposite of the direction of rotation of the crank/flywheel. Same effect.

 

[NukeMMC]

Equal and opposite reaction. If you are accelerating and forcing the bullet to spin at 180,000 rpm or so, the same amount of force is imparted in the opposite direction to the barrel/rifle. Not too noticeable in a .223 or .308, but definitely noticeable with my .338 or .416. Open the hood to your car, rev the engine, watch the motor torque to one side, the opposite of the direction of rotation of the crank/flywheel. Same effect.

So if you're spinning the bullet CCW when looking from behind (LH twist) what is the rotation direction of the equal and opposite force being imparted on the barrel?

 

[krw]

Yrs ago I shot a TC Contender pistol in 45-70. Not only did it recoil but it would actually “twist” in your grip. Been yrs and dont remember which direction but would be a good experiment for someone that owns or has access to one.
Let LL kik in on this. He’s fan LH twist bbls and He will know. My next 6.5 bbl gonna be 9.5-8.5 gain twist LH. Krw

 

[hlee]

I've never noticed twisting of a rifle while firing it, but I have seen video of the effect. My vague understanding is that this is a more noticeable effect on big bore cartridges (like the 45-70 mentioned above). It would also be more noticeable in light weight rifles. It may be splitting hairs in short action 6s and 6.5s, especially those 20+ lb rifles used in PRS/NRL competition.

 

[pmclaine]

Definitely feel the twist when shooting pistol one handed.

The ill effects are mitigated by proper fundamentals.

Id say LHT would be one of those things that provide incremental advantage but in a sport with as many variables might as well latch on to those things that work in your favor.