Dave, To answer your question...
I would think the variables in mid bead placement on the various barrel lengths you provided probably has a lot to do with the variables of stock DAC & DAH on those same guns... A shooters head higher or lower on the stock will directly effect the mid bead dynamics in relation to how it lines up with the end bead and a distant target... Thus mid bead placement being located in a multitude of places has everything to do with the limitless combinations of DAC & DAH dimensions of your stocks... JMHO... Hope this helps...
Best, CSL
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