Went to the range with a friend. I have a Bushy Dissipator (16") with a Aimpoint Comp M XD. He has a Colt Accurized Rifle (24") with a Leupold Vari XIII 6x20x50. We were plinking at 100 yds. and both were sighted in right on the money. We decided to swap optics and see how the others work on opposite weapons. Problem is neither one of us could even hit paper. So we swapped back and they were right on zero again. Questions are.
(1)Is this normal?
(2)Shouldn`t the picatiny rail be in the same location to the barrel on both weapons?
(3)Or is this just ballistics difference between 16" and 24"?
[thinking]

1)Yes, it's normal.
2)Not necessarily.
3)Very little difference between the two, certainly not enough to keep you off paper.

What the difference was the point-of-aim difference between the two rifles, IMO.

If you just swapped optics, without re-zeroing, then it's expected that the point of impact between the two scopes will change.

Even with tight tolerances in the manufacture of individual parts, the rifle become more than the sum of the whole.  When assembled and headspaced, each rifle will have it's own unique characteristics.  Combine that with the difference in mounts and optics, and you can't expect each rifle to act the same with just an optics swap.

how many different forums are you going to post this question to.

Same solution.........get a colt