Or, one could deduce that use of the tuner to get the last ounce out of that barrel being that the tuner doesnt tune the powder load, it tunes the barrel! .
Jerry, your statement above leads me to believe that you regard powder-tune as something entirely disassociated with bullet-exit-timing, suggesting that there is something magic about a specific powder charge whether it results in optimum bullet exit timing or not. I do not believe that! I believe that once you get into a reasonable window of muzzle velocity, ANY charge such as 27.5, 28.1 or whatever can be made to shoot well as long as the tuner has the bullets exiting at the proper point in muzzle upswing. That's hard for me to put into words but I hope it makes sense.
When running a ladder test by increasing powder charge in .3 grain increments, you encounter an in-tune condition about every 1.2 grains of N133. IMO the reason a specific charge such as 28.8 grains shows 'in-tune' today under specific atmospheric conditions is because it results in optimum bullet exit timing, not because of some magic combustion phenomena that always occurs with that specific charge. Tomorrow morning, 28.8 grains may not shoot in a basket with the tuner set to where it is today when it shot great. But,,,,,by making a couple of small tuner adjustments thereby changing barrel vibration frequency to optimize bullet exit timing, the rifle comes back in tune.
Most of our 6mm Sporters shoot well in three different windows of muzzle velocity;
1. Starting at around 3200 fps.
2. Mid range velocity around 3320
3. And the upper window at about 3440.
Some shooters even go up into yet another, ultra high velocity range by using around 30.6 grains of N133 which results in a muzzle velocity of over 3500 fps. Their reasoning is, "The faster they go, the less they blow." But case life suffers, barrels wear out quicker and it puts great demands on the case sizing operation to prevent stiff bolt operation.
IMO, when you exceed about 3375 fps in our 6mm BR rifles, using 64 to 68 grain bullets, you are bucking the law of diminishing returns. An expert in external ballistics will tell you that the reason bullets drift in crosswinds is because they are constantly decelerating, not because the wind is 'blowing them over.' Atmospheric drag increases by the square of the increase in velocity so launching bullets faster causes them to decelerate quicker which results in MORE wind drift, not less.
Hope this helps
Later, Gene Beggs
