TargetTalk

The question of torque settings troubles me. The barrel vibrations (aka harmonics) are changed because the torque setting of the action mounting screws (aka king screws) alters the compression of the bedding between action and stock. This alters the stiffness of the mechanical coupling between action and stock.

Barrel and stock act as separate masses, coupled together by a variable and 'lossy' spring (the bedding). How vibrations pass from one mass to the other depends on the nature of the intervening coupling. If vibrations pass into a well-damped medium, they will die out quickly. If the junction is such that vibrations pass poorly, energy will be reflected back, causing the barrel vibrations to persist, and perhaps excite resonances (the so-called harmonics). Wood is, to some extent, a lossy medium, which damps vibrations; most metals 'ring' if excited. This is why loudspeaker cabinets are not usually made from metal and one reason why alloy stocks are thought less forgiving than deader wooden stocks.

Using a bench clamp fixes the stock rigidly to the massive bench. Induced vibrations in the stock will therefore be coupled to the bench, via whatever properties the stock-to-bench interface happens to have. Indeed, variations in barrel vibrations can be expected to depend on how tightly the clamp is done up. This is a very different situation from shooting from the shoulder, when the stock is coupled to the (well-damped) shoulder by another (very) compliant junction. Barrel vibrations in the clamp will be different from when at the shoulder. Some test benches allow the rifle to recoil much as it would at the shoulder. I cannot believe that rigid clamps allow meaningful testing, and therefore torque setting optimization using a rigid clamp will not optimise the system for anything other than shooting from a rigid clamp.

What do you think?

I agree with your assumption that placing a rifle in a shooting rig it effects the setting of the complete system - barrel/reciever/stock.
I have an interview with Dieter Anschuts (aprox 12 years ago), where he states that they check the new rifles in a shooting rig, but when they tune the rifles (testing ammo) they use a scope and sandbags and "shoot from the shoulder".
Also, on the ISSF site you can find an article that states that even the best shooting rigs do not return to the same point after the shot has been fired and therefore do not give an optimal result.

Albert
The Netherlands

I think that if you are testing the material, a clamp/bench is perfect.

If testing rifle set-up, equipment ... shoot from the shoulder.

I shoot a 2013 and the 4 action screws are very touchy. A few NM here and there enlarges the grouping ability...from the bench.

I never could determine if torque settings affected my scores though. There are other errors manifested by my 50 yr. old body/eyes when shooting rom the shoulder.

Mike T.

How many out there test ammunition for consistent muzzle velocity?

I can't see any point in messing about with the characteristics of the barrel+action to stock coupling, by altering the torque of the king screws, unless the ammunition is known to deliver the bullet to the end of the barrel at a consistent time after the firing pin is released. If the 'barrel time' is not consistent, the vibrating muzzle will be in a different position for each shot. Trying to minimize the group size with the torque wrench is attacking the wrong problem.

Comments, flaming arguments, bouquets, whatever, please: this subject has really got to me and it's driving me nuts!

The most important aspect in rifle shooting is consistency. Assuming you lot test ammo for grouping in your rifle, using correct torque settings every time you shoot will introduce another known quantity.
The more known quantities you deal with, the less guessing and hoping you have to do.
A main adavantage of the newer aluminum stocks is the fact that swelling and distortion is a non-issue, taking out one of the bigger unknowns at match time. Again, consistency in harmonics. Bedding a wood stock accomplishes the same to a lesser degree.
Keep in mind that aluminum expands and contracts with temp change, therefore changing the tension on the action screws, wood a little less so.
Some shooters loosen and retighten the action screws before every position change as part of the rifle setup.
Varying from the suggested settings may bring more consistency with a particular lot of ammo, but will hurt with another lot. Again testing will reveal consistency.
I stay with the Anschutz settings and test different lots of ammo to find those that will group well.
It is best descibed in 'Ways of the Rifle': "Shooting ammo without testing for group is wide eyed innocence".
All of this suggests to take off the flat head screws, (if you are still using them), replace with hex screws and invest in a torque wrench. Check your torque at least every time go to the range. This ensures consistency and keeps unknown gremlins out of your training and matches.