Note : test barrels 2 & 3 were 35 inches, barrels 1,4,5,6 were 31.5, barrel 7 was 29 inches at test.
![Image](http://i1373.photobucket.com/albums/ag369/sierra39/TestBarrelVelocities_zpsea530f41.jpg)
This test was based on the highest centre count at 1000 yards with factory ammunition
Note: 1-14 was 29 inches
![Image](http://i1373.photobucket.com/albums/ag369/sierra39/TwistRate1000Yards_zps8cbd41eb.jpg)
Note: In this slide shows how a 29 inch barrel performed against the 31.5 inch barrels. It was cut short to see how the compensation would compare and out of a larger groove size to increase bore time a bit with the factory round. The test was done with relatively clean barrels to magnify extreme spread without warm up shots.
![Image](http://i1373.photobucket.com/albums/ag369/sierra39/ExtremeSpreadTests_zps1b45477c.jpg)
Below:
The slide below is with an unturned barrel. With a fundamental tuner weight it could be made to shoot better, but imagined what it would be like with reloads other than the factory rounds used for testing with a low extreme spread.
![Image](http://i1373.photobucket.com/albums/ag369/sierra39/Itsmorethangoodammo_zps3eadc77a.jpg)
![Image](http://i1373.photobucket.com/albums/ag369/sierra39/BarrelFlip_zpsd8c92097.jpg)
![Image](http://i1373.photobucket.com/albums/ag369/sierra39/Whatisyourbarreldoing_zpsbfd3d2f4.jpg)
If your barrel is flexing in the vertical, a barrel weight at the muzzle will dampen it.
However, groups may arc, clump laterally with or without fliers or string diagonally. In the first case with the overtones they can be induced by the rifling and returning vibrations as per OCW tuning or could be from action/barrel joint and pressure placed on that by headspace variance. But rifling torque may be seen in slender barrels, resulting from a tight helix of rifling or a mismatch in engraving forces on projectile by bore and groove size or how the relative stiffness of the barrel is aligned in the vertical plane. Multiple flexes can be sourced from the interaction of all sorts of whips and overtones including bullet slap from concentricity problems. Diagonal strings can be offset a bit by re-indexing the barrel by looking how your groups form at 140 yards by the appropriate degree before 12 o’clock. Arcing groups a probably better solved by reducing charge or changing powder. Of course shorter thicker barrels can solve a few problems assuming the bedding is sound. In the old days, barrels could be less than 26 inches, so cutting off 1 inch may amount to a decrease in velocity of about 30 fps but cutting off long barrels (35 inches) only gave about 12 fps per inch. This demonstrates the marginal gains in velocity by addling length.
![Image](http://i1373.photobucket.com/albums/ag369/sierra39/Arebarrelsalwaysinverticalplane_zpsc43e6e43.jpg)
![Image](http://i1373.photobucket.com/albums/ag369/sierra39/RiflingInducedTorque_zps1cb05aeb.jpg)
![Image](http://i1373.photobucket.com/albums/ag369/sierra39/Multipleflex_zps403ca81c.jpg)
![Image](http://i1373.photobucket.com/albums/ag369/sierra39/UnderstandingRifleTuning_zpsee04a502.jpg)
Below: Read the graph right to left. Its habit because that's how you set up drag charts.
The general trend of the barrel is negative. Edit: This was first determined by 25 yard tests with special loads then the subsequent free flight frequency test was done at 100 yards. But the factory load negativity is still evident. You may get positive compensation with .020” free flight, but probably with a fundamental tuning weight mounted so the weight extends past the muzzle.
Free flight at .040” is fairly neutral and is indicative of a tight nodal tune as well but could run a risk of falling off a node in bad environmental conditions or where moisture can corrupt your powder. Remember if you fly, it takes at least two weeks for your powder to settle as it takes on moisture in flight at 30,000 ft., unless it is sealed. On the other hand, if during the day soon after flying, and you are exposed to high temperatures, the moisture will not only come out of the powder, the atmospheric density changes will have you slipping steeply to the right off the node. You are in for a shocking shoot at the longs with elevation all over the place. That aside, there is no need for a tuner in this situation and you could comfortably sit back off the node @ .037”.
A light variable tuner would be very suited at .040" jump and you could easily get that slightly positive compensation.
After .040", you are in negative territory as low shots never catch up.
![Image](http://i1373.photobucket.com/albums/ag369/sierra39/FreeFlight_zps835e2366.jpg)