Arrow spine puzzle

[bowslinger]

I have shot a Herb Meland 3-piece Pronghorn 59#/28 inches for several years.  Best arrow flight from Easton 2020 Legends with 145 grain points or Easton Camo Hunters 2117 with 175-grain points.  I recently picked up a Herb Meland 3-piece Pronghorn all osage, 51#/28 inches.  I started out with 2016s and 2018s with various points.  Turns out even though the second bow is 8 pounds lighter in draw weight, it shoots the same arrows as the heavier bow.  Made this determination by bare shaft tuning.  Not sure why.  Difference in limb wood?  Issues with release?

[Wudstix]

I have bows ranging from 63-68# that shoot pretty much the same arrows and points.
            

[achigan]

One factor is how close to center cut the bowyer made them.
All draw weights aren’t equal in cast either.

[Orion]

Agreed.  The arrow shelfs may not be cut the same.  Some other things to look at, is the string material the same on each? Brace height the same? If the bows are slightly different eras, he may have changed the limb pad angle, limb design, from one to the other.

Regardless, it's really not that unusual to have bows of different weights shoot the same spine arrows.  I find I can overspine most of my bows by up to 15#.