?????
Of course they do.... the only way a bullet that's running 40fps slower than another to hit the same poi is for it to be launched "higher", at a steeper launch angle. Two football passes can reach the same receiver, one a lob and the other a bullet......but only because the lob is sent higher.
al
Al, I understand your analogy with the football passes but I do not believe it applies to tuning/shooting a rifle.
Yes, if the shooter had some way of knowing which round was going to be slow or fast, he could compensate by holding a different point of aim but that is not the case.
I am well aware of the sine wave that results from gradually increasing the powder charge and its affect on grouping. Vaughn describes this perfectly in his book, "Rifle Accuracy Facts" chapter 4 under, 'Special Benchrest Gun Problems.
On page 85, Vaughn suggests that one should operate on the 'peaks.' By 'peaks' he means the stop of the muzzle at the top. I have found equally good results operating at the stop at the bottom.
Regardless of the load, my tuner can switch the bullet's exit timing from a positive peak to a negative peak by rotating exactly one revolution. If the rifle is completely out of tune, the bullets are exiting in the middle of the swing where variations in velocity cause maximum vertical dispersion. In this case one can get the rifle perfectly in tune by turning the tuner a half turn in EITHER direction. Making a half turn in one direction times the bullets exit to coincide with one of the stops of the muzzle; a turn in the opposite direction times it to the other.
I have seen no difference in grouping whether the rifle is tuned to the top or bottom stop.
Hope this helps.
Later,
Gene Beggs