I took my new AR build to the range finally. I was not able to get it fully sighted in as I had to cut my range time short but the scope is shooting low. Very low. Now I managed to get the elevation proper and it's not maxed out and I do have a few clicks left but the knob is so high now (counterclockwise which rotates the know up to raise the POI) that when I put the cap on the scope it's rotating the knob down clockwise. I'm not forcing it either. I think it because I'm using ring reducers and one may be thinner or thicker than the others but in any case I'll probably have to take the scope off, shim it, put the scope back on and re-zero it.
Question is if it's shooting low and nearly maxed out should I put a shim under the scope on the front or back? It's a one piece scope mount as well. I have looked around but everywhere where it gives a straight answer some say front and some say rear.
Verified answer
I have had this same problem.
Turn the elevation adjustment all the way one way, then turn it all the way the other way and count the clicks, then turn it back half way to center the crosshairs. Put shim(s) under the scope on the rear mount. If you don't have any shims you can cut some out of a Coke can. It may take several shims. Take the upper off and bore sight it and tinker with the shims until you get the scope elevation about right, then take it out and shoot it.
Think about it like this: if you raised the rear of the scope until the scope was looking at the bullet holes on the target then you would be sighted in.
You can get any rifle on target, within 12 inches or so, by bore sighting on some object that is about 100 yards away. I set up my rifles on sandbags on the kitchen table and bore sight on a stop sign at the end of the block. Aim the bore just a little high to allow for bullet drop and center the crosshairs on the boresight target. That should get you on paper.
If you are going to tinker with guns do yourself a huge favor and buy a caliper. I use mine all the time. If you had a caliper you could check to be sure the front and rear rings, and the ring reducers, are the same height.
http://www.midwayusa.com/product/604242/frankford-...
First thing I would do is swap the ring reducers and see how that changes things. If you want to use your existing mount, then try a 20 MOA riser, such as:
http://www.amazon.com/Weaver-Flat-Riser-Rail-20MOA... , but it will probably add at least 1/4 in height.
Or you could just get a proper 1" mount.