Bill I understand a lot of what you are saying. Your ideas on how a tuner works were the first I read and as such were the first I took to be correct. After reading a bit more Im not sure I still follow everything you say compared to some of the other explinations out there.
This is what I see you saying is the reasoning for centering the parallel node at the end of the barrel:
These are of tuned barrels with the node at the end. In this the top is the average round, the middle is a fast round with a shorter parallel node, and the bottom is a slower round with a larger parallel node. The dashes are the other half of the node that would be there if the barrel continued.
If this is correct I see how it gets ammo of different velocities to leave the barrel at the same parallel line. But is that what you want? I don't think it is.
Here is how I see ammo acting that leaves parallel to the chamber in the parallel node model:
Again the top, middle, and bottom are the same three average, high velocity, and low velocity, respectively. With ammo leaving the barrel at the same angle every time I would think that fast ammo would hit high, slow ammo would hit low, and the average ammo would hit in the middle of the two.
From everything I have read on tunners they seem to help minimize the impact of velocity spread. I would think the parallel node model would give consistent results in that the barrel is in the same position every shot. In this if we knew ahead of time what the velocity of each round would be we could predict where that round would hit compared to the average. That isn't the case though as we only know velocity after it has been launched. As such it would seem that this would only help groups in that the left-right aspect would be taken out a bit due to the weight on the end.
Please point me where I am missing the boat here because I am really having trouble seeing the benefit the parallel node model has when velocity isn't consistent. Maybe velocity is consistent enough in quality ammo that the differences are miniscule, I don't know. I have read a bit and see the points people have that question if a parallel node is physically possible. I know which way I lean on that stance but I want to keep an open mind both ways until I have a firm understanding of both sides of the story.
After reading Varmint Al's stuff I can see how his idea works to minimize the effect velocity changes have on group sizes. If I understand his idea right a correctly set tuner has the average bullet leaving the barrel on the up swing, towards the top of the swing. Leaving towards the top of the swing allows a slower bullet to leave later but at a higher point in the swing which counteracts the extra drop the slower bullet has. A faster bullet leaves earlier at a lower part of the swing. This lower angle gives less rise in the bullets path which the extra speed gives less drop, again counteracting each other. The problem I have with this model is that it assumes the barrel movement is always the same at the same speed and as such a slower bullet leaves at a higher point and a faster one at a lower point. I would think a slower bullet would have a different effect on barrel vibrations that also would have to be taken into account. Maybe it is and I just didn't understand what I read. Varmint Al seems to have gone through a lot of modeling and testing to give the results he has. That said a biased test is no better than an educated guess so until both models are explained a bit better to me I am still up in the air as to what I believe actually happens, if anything.
