Stock Rigidity

[albow]

Hi

Looking for others thoughts around stock rigidity. I am in the process of condisering a new stock design for my LG though the design / construction method should see it be rather stiff.

The question is, can you make a stock too stiff or rigid to the extent that it actually affects accuracy due to vibrations and resonance that is retained in the stock when a shot is fired?

I am interested to know peoples ideas, thoughts, experiences or theories.

[macca]

Hmmmm. You and Jacko should talk.
I am wondering about this too.
Always believed in the rigid idea but wondering now how the recoil energy is moving through my stock and just what it's affecting.
Long time since I sat in a physics class.
Be interested in peoples thoughts as well.
Cheers

[Brad Y]

Have never really seen any of the ally or stocks shoot well and more importantly agg well. By that I mean chassis style stocks. I think there can be a point where too rigid could be detrimental in terms of getting a rifles harmonics happy. But I would be trying to keep things pretty firm around the action.

[The Raven]

I’m not expert but as no military uses rigidly mounted guns we have an answer.

To me, the more rigid it is the harder it is to dissipate recoil forces. You want to absorb and dissipate energy not have it bouncing around in the stock and possibly back into the action.




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[albow]

Hi Macca, yeah I have been chatting with Jacko and know his thoughts

Do you have or have you had any very rigid stocks and if yes how have they shot?

I know that I have videoed a number of my stocks and watched them back in slow motion to see how they react. Can be quite interesting.

[macca]

Hi Macca, yeah I have been chatting with Jacko and know his thoughts

Do you have or have you had any very rigid stocks and if yes how have they shot?

I know that I have videoed a number of my stocks and watched them back in slow motion to see how they react. Can be quite interesting.

One real rigid alloy one that was okay as far as grouping but the recoil was fast and you knew you were shooting it. The best stock I have is a Rob Eager laminate with some carbon fibre. It is light weight low set and when videoed doesn't torque as much as my fibre glass or laminate without the carbon fibre.
So I am a bit on the fence at the moment. The calibre in question can make the issues much more noticeable. My 280ai in lg torques big time (should have used the offset stock). The 6br is a pussy cat in comparison.
So I will be experimenting a bit.
Cheers

[albow]

Hey Brad I haven’t had too much to do with the solid alloy stocks though Jeff H here shoots one in his HG and I think had one on his LG. I have played with alloy / timber laminate along the same lines the same as JR has in his rifle and while i never got a real chance to do too much with mine I know JR had some pretty good results and aggs over the years.

Raven whilst the military doesn’t rigidly mount their guns, and i am no military expert, though i think theirs might be more associated with the amount of recoil they need to deal with and trying to absorb that..... dunno


Macca

What is a Rob Eager stock? Had a quick look on line an didn’t find anything. Do you have a photo or a link i can look at? You are right about the recoil and will be running my 7mm or 6mm in it so recoil will be heavier if running the 7mm. I am looking to keep the wide foreend which works a treat in handling the recoil though. Just going to make it a lot lighter so I can get back to a stretcher tube.

[Tony Z]

Rail guns have been steel or alloy construction for decades and are without doubt the most accurate rifles on the planet. Universal receivers used for decades are blocks of steel bolted to steel or concrete slabs with a barrel screwed in and are used by all bullet manufacturers for QA in test tunnels. Charles Bailey shot unheard of groups at 1K 20 years ago in the "USS Enterprise" all steel and alloy 120 pound gun right up until they changed the rules to prevent him competing.
I believe Jackos recent stocks have utilised the alloy ribs we have used since the early 2000s Alan. I would say Jacko is using very rigid stocks and has done so for some time. The question of rigidity is rather obvious with the above examples. As for resonance, carbon fibre and kevlar are about as bad, or good, as it gets if you are refering to transference. Personally i think resonance only plays a part when it's inconsistent. Same goes for flex.
It is not what it's bolt to, it's what it's bolted to does before the bullet leaves the barrel. Weight restrictions mean compromise. That compromise results in flex and it is that flex that determines the way the barrel and action and even the stock in combination flex. If you recall our discussion the other night i mentioned the guy who bolted his Stolle to a fence picket to prove that stock resonance and design was horse shit. Well yes he won a match and proved that a 50 cent pine board can perform as good as a thousand dollar piece of glue and balsa. But he is both wrong and right. If you recall i had two stocks for the Diamondcrap. The SGY and the MBR. The 30 inch barrel in the SGY stock had vertical that could not be cured. The MBR was longer, stiffer and had more rear bias resulting in better balance and less instance of the comb leaving the rear bag and becoming airborn, a trait most SR BR stocks show when put under some recoil. The same load used in the SGY shot little to nil vertical in the MBR. Same action barrel scope etc, but vast change in the way it reacted during recoil. It's not how it looks, or what its made of, its how it reacts to recoil. Then the next recoil and so on. My judgement is the SGY fore end was too short placing the weight bias too far forward when using the pedestal rest that left the butt end light and swinging in the breeze and never tracking consistently in the vertical plane under recoil. Sounds easy to fix but with weight restrictions, velocity requirements and rules confinement its not always straightforward as we both know. There was not a great deal of weight difference between the two stocks but worlds apart in geometry. The fix was geometry.

Tooley wrote a very detailed, and long article over on BRC of what is required in a stock and how that led to his MBR design and subsequent clones. If you read it and look at the mathematics around the lever principles, torque and center of gravity effect, it will alter the perception of what is actually the physical requirement of a stock. It basically says, deliberately or not, the Scoville and clones geometry is wrong way Corrigan for something with recoil and long heavy barrel. A bit unfair as the US rules have very black and white measurements and angles for SR BR stocks. Nonetheless it is probably why none grace the winners lists at 1K with something running a bit of recoil (torque) like you do. If you go that route, the math says no and i wholeheartedly agree from lots of fails to my name. A stock to my mind is about right when it places the rifles balance point between the action screws when fully assembled. If the three contact surfaces are on plane vertically to the bore, the tracking is inline and not curved which is regarded as the death knell. Why i reckon stocks should be machined in a mill and not molded. Or angle adjustable as some latest offerings indicate the importance of this.

I think you may be chasing a phantom here Alan. Our range will never show the best of a rifle since the ground alterations and the illegal population growth down there in Mehico sent the planet off its axis fucking up our wind vectors. Scores are one thing, but small groups on our range are a distant memory. I've seen your guns over a long period. They're perfect. The range sucks.

There is of course a very simple fix to this Alan. Build a heavy gun. Then you will truly see how much the range sucks for 10 shots.

[albow]

Hey Tony

I know what you are saying about gun set up and balance have a big part to play in how they perform. My current wide foreend designs seem to be very comfortable with handling recoil etc so not going to be changing that side of things. It is more where I am considering carbon within the build to give the rigidity without the weight and the resonance that may come from it which you mentioned below that is my concern.

I know Jacko has been playing with stock designs that have had carbon reinforcing laminated in like the aluminium that has been used by the likes of JR, you and me in the past. He is not sure it has been the best decision as he has not been able to get those rifles to shoot like his old rifle he set all the records with. Again this is another example that raises concerns about using the carbon.

My LG now is a composite and it is actually quite amazing how much things move when you watch slow motion video. Similarly my old laminate timber stock is the same, it moves a reasonable amount too.

Maybe I just need to build a carbon stock and slow motion video it to see what they do and compare the results on paper? The thing is I didn’t want to spend the 100 plus hours in the shed for no benefit though I keep telling myself it won’t be that bad because it is not summer and 40 plus degrees

[macca]

Rob Eager made the stock Rod Davies won the worlds with. He doesn't do it professionally.
Several of his stocks have done well in F open and Fly.
Cheers

[macca]

Nothing really radical . They just really work.
Cheers

[Tony Z]

Nice stock Grant. The low rider fore end is something the MBR could use. And an offset.
Is that carbon fiber ribs between the laminates?

[bobeager]

Yes Tony, c/f between 12mm AA marine ply. Nothing scientific, seems to work. I only make these one off for a few people that get referred. Do not use a duplicator, Build each stock up in layers from the "inside out". last thing is hand shaping. These days only work with Barnard P and the V block.

Cheers Rob

PS: the one I made for Rod Davies was a bit radical, his design.

[stinkitup]

Is the barrel fully bedded on that stock or just bedding compound in the forestock for a reason?

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[macca]

Is the barrel fully bedded on that stock or just bedding compound in the forestock for a reason?

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No bedding persay a v block for a Barnard P action. Barrel fully floated.
The dark is carbon fibre for strength. Rob can correct me if I got that wrong.
Cheers