Different optics have different reticle designs. Most ACOGs come with a 100m aim point, and so is Elcan spectre. That is what the manual said.
On the other hand, if you know how to use a ballistic calculator and with a bit of intelligence, you can formate different ways to zero your sights with different type of ammo.
For example, I zero Elcan Spectre, ACOG and aim point, anything with a 1.5MOA or 2MOA dot, with a theoretical 150-160m zero. That little deviation of 1/2 MOA means nothing for the range and target type that a 5.56 carbine is supposed to use against. On the other hand, you can now do point and shoot within 200m. It an area is touched by the dot, it gets a hole.
Even if you zero a 100m aiming point at 200m, that is only 1.5MOA or 0.4ish mRad of difference. 1.5 MOA of error can be easily made by 50meter'ish misjudgement in range estimate. Shoot high and adjust. It is a waste of effort to worry about or being super anal about "matching the BDC" down to a meter with a 4X optics and a rifle that shoots 1.5 to 2.5MOA. Once it is out in the field, range estimate and some change in angle means one way or the other you need to be fast on your feet to adjust fire. If you need to be more precise, you need a different rig and a laser range finder ( you are good ranging targets)
Final thought, the 50/200 cross over is a 5.56 thing that works with AR15 using a typical bore over sight distance of 2.5". It doesn't work nearly as well with TAVOR that has a much higher sight over bore distance. It is a rule of thumb for most AR15s shooting 5.56, but it is NOT a law.
