Howdy front sight,
Looks like a nice scope. Your range cam is a military model. There are two basic versions, one marked for 300-900 meters (3-9) and another marked 1-10 for 100-1000 meters (allegedly...) We can't tell which you have from the photo.
On the 1-10 cam, ignore the 1, 2, and 10 markings, they are pretty much useless. They didn't change the machining from the 3-9 version, just added the 1,2 and 10 markings and those settings are not on the trajectory curve.
If you are hitting high at 100, here are the first things to check. Center the elevation and windage adjustments on the scope itself. You can either turn both knobs stop to stop, count the turns and split the difference (don't force the knobs at the limits, as soon as you feel resistance stop turning...) or, in bright light, put the objective end of the scope against a mirror and look through the scope. You will see the reticle and a mirror image of the reticle. If they are not aligned, the reticle is not centered. Adjust the windage and elevation until the reticle and the mirror image are aligned, now the reticle is centered.
Next, there is an adjusting screw for gross elevation adjustment in the scope cradle under the range cam. This screw makes large elevation adjustments, use this to get close, then make final minor corrections with the elevation in the scope. Hold the screw with a small flat screwdriver and loosen the nylock nut. Turn the screw upwards, raising the rear of the scope, to add elevation, turn the screw downward to lower the rear of the scope to lower elevation. Starting point is lower the screw until it loses contact with the cam, then turn it up until it just barely touches the cam ring. Hold the screw there and tighten the lock nut.
I must ask whether you are using a proper rear stripper clip mount. That is an essential part of the system, and if you aren't using one you will probably have elevation problems.
There are two options for this. The Army machined each rear mount custom for each rifle. Mount the scope with the front bolt, mark the location of the rear mount bolt on the side of a standard USGI stripper clip guide, then drill tap and countersink that hole for the rear mount bolt. This provides a perfect custom fit for that mount on that rifle and eliminates some dimensional problems found even on USGI M14s.
Option #2 is use the rear mount made by Leatherwood for the commercial market. It is predrilled, but because of dimensional issues with various receivers it may or may not work properly on your rifle. I am using one on a SAI M1A 047XXX vintage and it fits perfectly, YMMMV.
Also, be aware that when zeroing the ART II Government Model on the M14 type rifle, at 100 yards with the scope set on 300 meters, the bullet should impact about 5.6" above point of aim. This will be close to zero at 300 meters. (for typical 173gr/175gr match loads similar to Federal Gold Medal or M118 Match or LR.)
