Yes, you would want the distance that the bullet base travels but for the shockwave, I assume you'd want the full distance to the breech.
I wasn't sure if your numbers were a round trip or one way.
If it's round trip,you'd want whole numbers, if it's one way you'd want even numbers, not the .5s I mentioned.
Chris Long has an excel version of the calculator here:
Still happily answering to the call-sign Peetza.
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