Purdy Calculation Question

R

Rimfireshooter

Active member
If you have experience with the Purdy Tuner calculation method, could you help me with a tuner question? I just received a new benchrest rifle made by KSS, with a Harrell's tuner on it.

I have been working on using the Purdy calculation to determine the set point to start testing the tuner at the 9th harmonic. My issue is that the formula result at the 9th harmonic shows a physical length of 27.162 inches from the bolt face to the end of the inner tube. When I measure that on the rifle, I have 28 inches from the bolt face to the end of the inner tube.

Since I have no way to shorten the length to meet the Purdy estimate, my question is do I go on to calculate the 7th harmonic?

When I did that calculation, the bolt face to end of the inner tube distance is 28.178 inches, so I do have room to adjust the tuner shell out to the calculated distance.

I moved the outer shell to line up exactly with the edge of the inner shell, so they are both the same distance, my tuner is reading a setting of 218, which is approximately where it is expected to be.

Is this the correct approach to setting the tuner based on the calculation by Purdy?

Thanks for any clarification you can provide.
 
Purdy formula

Rimfireshooter said:
If you have experience with the Purdy Tuner calculation method, could you help me with a tuner question? I just received a new benchrest rifle made by KSS, with a Harrell's tuner on it.

I have been working on using the Purdy calculation to determine the set point to start testing the tuner at the 9th harmonic. My issue is that the formula result at the 9th harmonic shows a physical length of 27.162 inches from the bolt face to the end of the inner tube. When I measure that on the rifle, I have 28 inches from the bolt face to the end of the inner tube.

Since I have no way to shorten the length to meet the Purdy estimate, my question is do I go on to calculate the 7th harmonic?

When I did that calculation, the bolt face to end of the inner tube distance is 28.178 inches, so I do have room to adjust the tuner shell out to the calculated distance.

I moved the outer shell to line up exactly with the edge of the inner shell, so they are both the same distance, my tuner is reading a setting of 218, which is approximately where it is expected to be.

Is this the correct approach to setting the tuner based on the calculation by Purdy?

Thanks for any clarification you can provide.
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