Tuned barrel

[Trevor Rhodes]

OK here is one for the experts. You have a tuner on a barrelled and scoped action in a vee blocked stock, the rifle is as accurate as possible. Now you change to a heavier scope or for this example the vee blocked stock your using is swapped for another vee blocked stock which is lighter. Now will the tuning change with either these alterations.

[williada]

Trev at some point across the course it will, unless the centre of gravity is aligned in the same way with the bore centre with the new scope on top and a new stock. If this different it will alter the fundamental whip. If you shoulder the rifle and the butt has a different height of contact point then that will also alter the fulcrum point and the fundamental barrel lift. How much it changes things can be offset if the butt contact counters any difference in boreline and centre of gravity. If the differences are marked the timing can be fined tuned with seating depth. I just add that a tuner weight will have an effect on the fundamental lift, but the tuner itself if it is a variable tuner works on the smaller reflected vibrations of harmonic frequencies in the general order of 3 to 5, not so much the fundamental vibration for fine tune.

[Brad Y]

Trev at some point across the course it will, unless the centre of gravity is aligned in the same way with the bore centre with the new scope on top and a new stock. If this different it will alter the fundamental whip. If you shoulder the rifle and the butt has a different height of contact point then that will also alter the fulcrum point and the fundamental barrel lift. How much it changes things can be offset if the butt contact counters any difference in boreline and centre of gravity. If the differences are marked the timing can be fined tuned with seating depth. I just add that a tuner weight will have an effect on the fundamental lift, but the tuner itself if it is a variable tuner works on the smaller reflected vibrations of harmonic frequencies in the general order of 3 to 5, not so much the fundamental vibration for fine tune.

Interesting to read about the shoulder/butt contact height. I have a rifle and known proven load. Recently installed a recoil reducer that I had in a previous stock that I scrapped because I couldnt get anything decent going (spring tensioned graco recoil reducer) and it turned the good rifle into what the previous rifle was. Throwing shots vertically up and down. Yesterday I removed it, put the original pad back on and threw the recoil reducer in the bin. Not sure if it relates to what your talking about David, but there’s no way I will ever go back to one.

[AlanF]

I'd suggest its not only tune that is affected when you change stocks. In my experience, point of impact can be affected by several MOA, in either vertical or horizontal or both.

[pjifl]

I always found that shooting from my right shoulder had a slightly different zero than from my left shoulder. More so for a high recoiling rifle. Not very surprising, really. But it does indicate that hold on a stock will have some influence.

Peter Smith.

[williada]

Yes, Brad and you were definitely affecting the fundamental whip with a sliding fulcrum point if shooting free recoil in this instance with a recoil reducer. There have been a few studies saying there is no advantage in using mercury or spring system recoil reducers in terms of accuracy, (not comfort) over fixed weights placed in the butt. They are responsible for vertical issues over a number of distances which Alan has noted can be by several minutes. That is why properly designed stocks are balanced for performance like you would balance a car wheel but on two planes, the vertical and the horizontal.

Will regards to horizontal, an offset stock which was a trend that was short lived in F Class, throws shots. It did not control the torque effects. So the weight off centre in the horizontal also poses a problem. Better to run with a symmetrical setup.

In F class, the point of stock balance in the vertical is due to our longer barrels tends to be a little further forward than bench rest stocks. Scope position along the setup will also effect balance. The height of the scope above the bore-line is another factor to consider. A scope mounted higher may offset the a deeper butt to align the centre of gravity with the bore-line. The closer this relationship, the less lift and more rearward thrust. However a little lift is desirable for a compensation tune and an harmonic tune and a more comfortable shoot. Longer barrels are more responsive to harmonic tune than short stiff barrels which control lift which are better suited to an OCW tune. If the setup is not right, then the harmonics are effected. Harmonic tunes are more suited to FClass than benchrest. The stock balance you read about in benchrest is a different ball game because of their setup for short range also has less recoil.

Those that free recoil can offset some of the balance issues for and aft with longer stocks in FClass. But they can't really eliminate issues of responsiveness to lift which remains a bore/centre of gravity issue of a better designed stock which also is associated with a tune type desired. I still like to have butt weight closer to the fulcrum point because I shoulder heavy hitters and I dislike too much forward weight. I further optimise barrel lift after I have balanced a setup with the height of my contact point at the butt. That's just the way I am and a legacy from fullbore days in TR.

I note the trend to heavy tuners. Yes, they work but it depends on the setup and the relationship to fundamental lift. I have a SAUM which is past its prime that has a light tuner which is suited to the lift determined by the stock/barreled action with scope setup which is superior. Albert will tell you it isn't bad if I compare it with his setup.

The variable component of tuners themselves are designed to effect the smaller flutters and oscillations of reflected vibrations which are subdivisions of the fundamental whip. So if the lift is right you don't need a heavy tuner.

What is most significant is getting the barrel lift profile right which can also be done without a tuner. The powder tune or barrel tune supplements that process. The platform is the most important and it is important that it fits you and your position is right.

[Gyro]

Yes Trevor all of the above. All ya gotta do to work it all out is a HUGE amount of range time ! I reckon lots of those supposedly small things have a large effect on how the rifle shoots and Lordy I’m still working out what they is myself ! Just that shoulder contact with a ‘free recoiling’ setup is my latest fetish and just that aspect alone requires a lot of attention to how you present your body to the butt, which then affects the LOP and your heads position relative to the scope ... a steeper body angle lets you more naturally use the shoulder muscles to gently and more important - controlably - contact the butt, which may be a more forgiving place than the more boney place ( the "pocket" ) that gets used for butt contact with a more straight behind position ... who said it was easy ?

[ErrolW]

All I can say look at the timber your using for your stocks. Look out side the box and think a bit different to everybody else dnt be a sheep. Bolt relief to front of stock has a big part in what your trying to control.

[Gyro]

Tell me about the type of timber please Errol ?

[ErrolW]

Look at the timber from your home island and tell me what you have growing over there. Timber density plays a big effect

[williada]

Yep, 33 inch pound for great absorption and resonance but not necessarily control of lift Errol.

[GSells]

What was the Question again?? Ok heavier scope !! Yes that scope in itself is just like a big tuning fork and this potentially can change the reflected vibrations and the tune or super tune of a rifle . I’m the only peanut that has silicone tape on my scope !
Ok if you move to a lighter stock ? Yes it could as David said it can affect barrel lift and reflected vibrations . This is why orings work and also notice the top tuner makers have some form of harmonic absorbing material in their construction.

Plan is to take out as much reflected harmonics as possible! This does one huge thing ! Makes the naked barrel very user friendly!

Ok funny how people are talking about shoulder position affecting groups ! Ok I am officially going to be a wanker and post a group !! Yeah I know !!!!
But on the weekend that new .284 w barrel was very user friendly! In that at 100 m it would consistently one hole group with a low shot every now and then ! I remember doing this a few years back . But having not shot more than 100 rounds since September last year because of Covid ! I was letting my rifle FREE RECOIL too much and letting it hit my shoulder and kicking the stock upwards !
I wasn’t preloading the stock as much as I normally do . But so many little things to remember!!
Regards Graham.

94079B11-76B8-4016-9B05-0101C6E0AFE8.jpeg

[ErrolW]

Its the nature of changing the beast using a lite weight timber with a strong stuctual integrity can change that aswell. F open stocks are a good example how many of them are close to or on the max in laminated stocks with parallel barrels with little to no weight to spare for tuners. If your a GRS say and your shooting ftr stock will weigh roughly 2.2kg with a barnard block in it, heavy varmint barrel ,p action . Niteforce scope and a bipod your nearly on the 8.25 kg limit. So what happens when you wnt to put a parallel barrel in that stock it cnt be done . Now say you build a lite weight timber stock finished at around the 1.2kg make with a block and recoil pad. You can either put a tuner on your current heavy varmint barrel.or put a parallel barrel in. Weight forward can be a good thing in all classes. In saying this recoil devices play a part as well you dnt need to spend big to control recoil or torque issues in a rifle .

[Gyro]

Its the nature of changing the beast using a lite weight timber with a strong stuctual integrity can change that aswell. F open stocks are a good example how many of them are close to or on the max in laminated stocks with parallel barrels with little to no weight to spare for tuners. If your a GRS say and your shooting ftr stock will weigh roughly 2.2kg with a barnard block in it, heavy varmint barrel ,p action . Niteforce scope and a bipod your nearly on the 8.25 kg limit. So what happens when you wnt to put a parallel barrel in that stock it cnt be done . Now say you build a lite weight timber stock finished at around the 1.2kg make with a block and recoil pad. You can either put a tuner on your current heavy varmint barrel.or put a parallel barrel in. Weight forward can be a good thing in all classes. In saying this recoil devices play a part as well you dnt need to spend big to control recoil or torque issues in a rifle .

Just be careful Errolmeister with going too light on the woody build ! Ya really really don't want to have a flexy stock maaaaate. Better to save weight on the barrel for an FTR build.

[Wal86]

Hey Trevor,

Changing your stock could change your rifles tune, how much your tune is effected depends on how extreme the stock change is..(weight, balance, material, dampening qualities etc./ eg. Timber to a Bolly stock)..

You never know Trevor the stock change may improve your tune..

In a correct setup changing your scope will have no effect to your rifles tune what so ever..

Cheers
Alan