Alloy stocks. Load tuning?

[Longranger]

A question for the gurus. Is it harder to find the right load with an alloy stock as opposed to a timber stock?

Personal experience seems to indicate that that is the case. Opinions?

[mike H]

A question for the gurus. Is it harder to find the right load with an alloy stock as opposed to a timber stock?

Personal experience seems to indicate that that is the case. Opinions?

Haven't got an alloy stock,so have no idea,however Alan Fraser has a steel tubing stock and it doesn't seem to hold him back.
Mike.

[williada]

What’s in a tune? It is the management of the vibrations, not just the fundamental lift characteristics but where secondary and tertiary vibrations in the main, coincide to form harmonic nodes as well. Some have claimed to have measured 9 interacting vibrations. So to get a more responsive tune whether it be a nodal tune, an optimum charge weight tune or a compensation tune, it’s a good idea to dampen some vibrations and work with others.

Aluminium stocks have a problem dampening unwanted vibrations and the wave length tends to be shorter with the secondary and tertiary vibrations. These are like pulses in a heavy Fclass barrel which are used to refine tune and tend to be choppy in aluminium stocks making it harder to find a stable section in the barrel in which to tap for tuning.

These stocks are tunable, as Nick S who was a pioneer of Fclass always used a gasket between his barrel and his barrel block. James C advocates with his aluminium Jerico stocks, a flexible sealant between the action and the aluminium stock. A manufacturer in WA uses the flexible rails like the Millenium stock to dampen vibrations on the aluminium bedding block. When I was using pillars, I always used flexible sealant on top of the pillars. A French manufacturer of aluminium small bore stocks has strategically placed holes in the butt which get larger and larger to dampen vibration. It is an issue but it can be solved. If the unwanted vibrations are dampened, its easier to pick the other important ones which alter bore size at the muzzle and bore exit angle for advanced tuning.

The benefit of an aluminium stock is that it will not deteriorate due to climatic factors and so cause a bedding problem compared to a wooden stock. So I guess, where you compete should be a factor in what sort of stock is better.

If an aluminium block is used in a wooden stock, the wood can absorb unwanted vibration. Again the density of wood must be about 33 inch pounds like that of walnut, mountain ash, Queensland maple or blackwood for the finest harmonic pattern. Note that mountain ash tends to warp unless it is laminated. The stock blank should be cut from quarter sawn timber, thoroughly cured and sealed to minimise shrinkage. But exposure to sun soon damages the stock with a tendency for it to warp. Then you get shooters who over tighten takedown screws and destroy the cell structure making the stock susceptible to humidity and movement.

There is no doubt that a wooden stock in top shape of the correct density produces the best harmonics for a shooter to tap into for a tune.

The resultant wave lengths tend to be longer and smoother and you don’t tend to fall off the node, as to speak, if the environmental conditions change assuming the stock is stable unlike a shorter wavelength which can put you onto a negative slope very quickly.

So if I was to make a generalisation, aluminium stocks are harder to tune and also expand in heat unless a flexible gasket system is used to counter the effect. Others may have different experiences.

[RDavies]

So if I was to make a generalisation, aluminium stocks are harder to tune and also expand in heat unless a flexible gasket system is used to counter the effect. Others may have different experiences.

I switched to an aluminium stock in my 7mm a while ago and kind of suspected that it was the alloy stock which made it more finicky than its previous soft balsa wood stock (when the rifle was in this stock it was just so consistent and hardly needed loads adjusting) . My 6mm in a wooden stock seems more like other peoples guns, not very finicky. What do you think I could use as a gasket between the action and aluminium bedding block? I previously had a flexi bed block in this aluminium stock and couldn't get it to work at all.
My new gun is an aluminium barrel block in a wooden laminate stock. What do you think of vibration control when using a barrel block in a laminate stock?

[Longranger]

Thanks David. It appears to me that tuning a load for an alloy stock is more finicky whether it is a tube gun or more conventional stock. My personal experiences concur with your observations. Load increments are necessarily closer or you will miss the sweet spot entirely. Ditto for jump testing.

Not untunable, but you certainly work harder to get a good result!

[williada]

Hi Rod,
By all means use a thin gasket paper in your barrel block like Nick S. Some put a smear of super strength Araldite to form a thin gasket which is easily popped in a freezer. Laminated stocks are fine, but I have several old Percy Pavey stocks which only use three laminates, two of blackwood for stiffness and the middle of Queensland maple to absorb vibration. The more laminates you have reduces the ability to absorb vibration because they effectively increase the density of the stock and shorten the wavelength of secondary and tertiary vibrations. David.

[williada]

Longranger its good to confirm these experiences. Cheers, David.

[johnk]

Back when the 94 world masters games was in Brisbane, a South African brought a prototype rifle over to shoot TR. It was largely a clone of the RPA in appearance but it had a T shaped recoil lug/alignment gizmo on the action bottom that fitted into a female cutout on the alloy stock. It shot like crap until the shooter took advice from a local & fitted a gasket cut out of a handy sheet of card. About the same time, the flat bottom Anschutz actions with a similar recoil profile were being tuned by the same method, or with plastic from an ice cream tub lid.

[williada]

John, if I also may recount that my wife in the late seventies ran 3rd in a big Melbourne Queens with a piece of playing card under the re-enforce that Peter Hallet stuck in and covered with graphite.

[Longranger]

I wonder if those Limbsaver barrel de-resonators would be a quick, dirty fix for some alloy stock tuning issues.

Ugly as sin, but no denying they do work although not my preferred method of tuning. Seem to be a few getting around the ranges these days.

[williada]

The answer is yes and no. I used one to top score in a Victorian Teams Championship in F standard and still use them even though I don't shoot competitively now. All they do is dampen unwanted vibrations and so take the chatter out of the harmonics which is why I use them. But they do not substitute for finding the tune hotspot which still relies on load development. David.