Torque Effect

[macguru]

Just a question about the rifle reaction when fired, but before the pill leaves the muzzle......

I understand the rifle lifts a little at the muzzle, but during projectile acceleration inside the barrel, the pill is 'spun up', clockwise in most cases....

so, does this mean the whole rifle in the rest is torqued a little ANTI-clockwise to compensate (conservation of angular momentum) (while lifting a bit as well) ?

Of course , even more so with faster twists and heavier pills...

cheers Andrew

[DenisA]

Hi Andrew,

I started shooting F-class with a 6BR. Last year I introduced a .284 and .300wsm. The rifle torque increses significantly with the heavier bullets and larger calibres.

And yes, as you've said, in the opposite direction to twist.

I really had to put more emphasis on technique. 6BR's are so beautiful to shoot, they let you be lazy.

I've been setting my digital camera on video mode, on a mini bench top tripod and recording myself, the gun and front rest during shoots to refine and correct my technique, and ..................................... I'm still crap.
The rifle torque can easily be seen in the reflection of the flat underside of my shiny stock.

[bruce moulds]

denis,
my rifle has rh twist and twists to the right when fired.
maybe it goes to the left first then bounces off the bag?
bruce.

[DenisA]

I'm pretty sure offset stocks normally have the offset to the opposite side of the barrel twist direction.

My opinions can only be based on my personal experience. It would be interesting seeing a vid of your setup Bruce. Maybe that would tell the story.

Also, I'm sure rifle torue and other recoil chracteristics would depend on the side bag, lower bag tension and general setup of the front rest, even the rear bag setup, shoulder tension and cheekweld.
Eg. Front bag side adjusted to firmly against the stock may drag against the stock causing interference with its natural inclination to recoil and allow bounce.

Mine is easily identified as I semi free-coil all cartridges and my setup allows the rifle to glide back smoothly.

Just a laymans point of view. Interested to hear other opinions and experiences.

[Norm]

denis,
my rifle has rh twist and twists to the right when fired.
maybe it goes to the left first then bounces off the bag?
bruce.

Bruce,
The rifle with a RH twist is under torque to the left while the bullet is in the barrel (not a very long time). It is a very small movement but as it takes place very quickly it is almost imposible to see. This small movement however contains considerable force in a larger calibre rifle.

The rifle will then react to the sudden release of the bullet as it exits the crown. The barrel actually twists slightly in this reaction like a torsion bar on a car.

Once the bullet leaves the barrel it no longer applies any rotational force to the rifle. The barrel is then free to return to its original shape and the rifle twists to the right in the process.

This reaction is also helped by the force that it has applied to the rest on its left hand side. This effect takes place over a longer period of time and is the one that is obvious to the shooter.

[macguru]

And I would imagine there is a tendency for the barrelled action to lift away from the stock a little bit.... These two effects, the rise and torque of the barrel before the bullet leaves the muzzle, would cause some of the curved groupings we can see.... but even if you clamped the whole thing down the barrel itself would still have a vibration of its own....

[bruce moulds]

norm,
thanks for that.
it makes a lot of sense.
bruce.