Rifle Torque

[CA_Shooter]

With a given weight restriction - IE: F-Class rules (22 lbs), to limit rifle torque and having the rifle track back nicely, if given the option to add weight:

Is it better to have a lighter scope and add weight to the stock OR is it better to have a heavier scope and not add the weight to the stock?

 

[bugman]

IMO, rotational forces are decreased anytime the center of gravity is lowered. There are a lot of "ifs" with your described scenario, but in general opt for a lighter optic and add the weight as low in the butt as possible.

 

[CA_Shooter]

IMO, rotational forces are decreased anytime the center of gravity is lowered. There are a lot of "ifs" with your described scenario, but in general opt for a lighter optic and add the weight as low in the butt as possible.

I guess another way to ask the question is: is it a bad idea to have a heavy scope and have more than the necessary weight distribution of the rifle be in the scope area instead of the rifle stock?

For example, and assuming your eyes love the scope, is it a bad idea to have a 3 lb Valdada scope and 10 oz rings on your in sum 22 lb rifle? Will this mess up tracking? In this example, is it a better idea to have a heavier stock and buy, for example, a 28 oz March scope (assuming that you like the scopes equally).

 

[jackieschmidt]

I agree with @bugman about the center of gravity thing.

Also, keep in mind, when putting a heavy scope on lighter components just add weight, more recoil force is transmitted to the scope and its mounts. It is not a huge consideration, but given the choice of where to add weight, it is better to add it to what absorbs the recoil, that being the stock.

 

[Rat Rifle]

Some very successful competitors shoot Valdada scopes. And on 17# rifles.

 

[CA_Shooter]

@bugman and @jackieschmidt - is the preferred location to add the weight in the low part of the buttstock as opposed to around the bedding area?

 

[goodi]

In MHO another alternative for reducing firing induced torque is to increase the height or depth of the butt.

 

[Sandstorm]

What bullet, caliber combination are you concerned about torque and recoil.
ie: Whats your application.?

 

[davidjoe]

Weight that is further away from the origination of the torque would dampen it. Torque originates along the barrel axis, so like a power drill with a long handle, weight that is further from that axis uses the distance as a lever to stop the torque, imagine a two pound rifle trying to twist 20 pounds of dead weight held out by a two foot long bar attached to the action.

The helpful effect of further distance perpendicular to torque is seen in fore end rule limitation to 3 inches. If that rule wasn’t in place width would jump to 5 or 6 inches.

 

[JEFFPPC]

All the theory is great . But the Indian determines the outcome. Of course trying to beat conditions with bigger case, heavier bullet, more powder really increases the torque but is seldom mentioned.

 

[goodi]

Correct me if I am wrong but wouldn't the base of the butt being wedged in position and being restrained by the rear bag ears (as well as the greater moment arm distance from the bore to base of butt) provide more torque resistance than the 1.5 inch distance from bore to edge of forend.

And wouldn't the inherent torque resistance of the butt increase proportionally with any increase with the height/depth of the butt.

Depending on weight distribution (say 50/50 of the complete rifle) both sides of the forend would transmit 25% of the rifle weight whereas the butt would transmit 50%.

 

[davidjoe]

Correct me if I am wrong but wouldn't the base of the butt being wedged in position and being restrained by the rear bag ears (as well as the greater moment arm distance from the bore to base of butt) provide more torque resistance than the 1.5 inch distance from bore to edge of forend.

And wouldn't the inherent torque resistance of the butt increase proportionally with any increase with the height/depth of the butt.

Depending on weight distribution (say 50/50 of the complete rifle) both sides of the forend would transmit 25% of the rifle weight whereas the butt would transmit 50%.

The stock can definitely be used to help, but there is a lot of thinking that favors minimal contact with it, and in my guns at least there is not much pressure downward on it, into the ears.

The 50/50 doesn’t turn out like expected. Here’s one of mine balancing by itself a few days ago at the range. I don’t normally use this type of stock in Fclass anymore, but as of yesterday, now I am.

The brown gun shot better yesterday than I have in a long time, with my conventional Fclass stocks.

 

[DaveTooley]

Moment of inertia - Wikipedia

en.wikipedia.org

Weight/mass further away from the centerline better.
You can't fool Mother Nature

Edit; ".The moment of inertia depends on how mass is distributed around an axis of rotation, and will vary depending on the chosen axis."

 

[BoydAllen]

There are two types of rotation that affect a rifle as it is shot from a rest. This discussion has been about the rifle rotating around the CL of the bore, and effect that comes from bullet weight and velocity combined with rifling twist. The other type of rotation comes from the rifle's center of gravity being offset from the line of thrust, which causes the rifle to rotate around its center of mass, around an axis that is perpendicular to the bore, running through the CG. Stock design can affect both.

Some years ago, before the current crop of pickle fork F Open stocks, I made an adapter for an old 40X prone stock that did something similar. The effect of how the rifle reacted as it was shot was quite noticeable. Things calmed down quite a bit. It tracked better, and torque seemed to be less of an issue. Although I do not have one, I believe that this is the reason for the longer stocks being used by top shooters in short range benchrest. Typically in that sport, state of the art stocks have the rear bag contact area as high relative to the line of the bore as is possible. I believe that free recoil shooting style is the reason for this. It may be less effective for torque control, but the extra length of the latest crop of wood and carbon fiber stocks might reduce that effect. What it does for sure is move the center of gravity closer to the bore, which has been demonstrated to reduce the amplitude of the vertical component of barrel vibration significantly.

As an aside a friend has an almost magical HV rifle that is perfectly balanced around the CL of the bore. He put a weight between the rings, on top of the action, that accomplishes this.

The bottom line in all of this is that there are so many variables that we really need to do testing to determine what the effect will be on the target, and in the bags.

Added a little later: One factor that seems to have been missed here is that for a given forend width the closer the bag tracking surface is to the bore CL the greater the effect will be for controlling the effect torque. If you look at the previously mentioned picklefork stocks they take maximum advantage of this. Here is a video of an unusual stock that has the bag contact very close to the barrel. The rifle is a .284 being shot free recoil with 175 grain bullets. It comes straight back, with no noticeable torque. It may be that the depth of the butt is also a contributing factor.

 

[Fuj]

I've been doing them for awhile. I also use them for my stop as in
the video. I have no forward stops on any of my rests. The stock
stop itself is just a way of me playing with weight and balance.
Going further, I'm looking at lowering the barrel much further into
the bag. with the forend much more on top. It would be more like
a flat plane, or go even lower for a pendulum effect. As I say, "Never
let a bad idea go to waste".

This is my 3". I have a 4" plate I bolt to it when an event allows, but
making a whole new 4" unit as I add another chassis to the mix.

 

[goodi]

just an example of a 1990's vintage 280 Ackley LRBR light gun with low bore axis and 5 inch deep butt designed with the aim to try and reduce firing induced jump and torque twist.

stock length is 44 inches

mid position one piece barrel block to hopefully minimise barrel vibrations ??

stock stiffness was tested prior to rifle assembly

cheers goodi

 

[Rocketvapor]

@goodi
Now trim weight so you can add a 3 pound, with about a pound each on 12" moment arms (24" wide)
and make F-open (22.2 pounds)