Trouble with sight-in elevation...

[schumi]

I'm now on my third 6.5x284 Lilja barrel on a Savage action. All three are different rifles. The first two had to have a 20moa base added to the action to be on target at 1,000yds. They also had enough elevation adjustment to go from 100 to 1,000yds. with no trouble. I naturally assumed I needed another 20moa base for this one. But today when I tried to get it on paper at 100yds. I ran out of down travel with about 24 inches still needed to be center. I took the base off and shimmed the front to elevate the base (defeating the purpose to a degree). I took the scope off and switched to sighting in the RPA open sites. Again I'm out of down travel and need about 4 more moa. I was using a Leupold BR24x. Now using the new Leupold 30x. I think the 24x had 72moa travel and the new 30x is 40moa travel. That might explain that nut the RPA site is a different ball game. I know I could just raise the front base but it shot fine on the same barrel before I had it rechambered from 260 to 6.5x284. Any ideas (besides moving the target back to 400yds.) ???

 

[BoydAllen]

It seems to me that your shimming would result in a bad fit of the base to the receiver, unless you also bed it. As to a work around, the first thing that comes to mind is the Burris Signature Zee rings. The inserts can be selected and manipulated to give you exactly what you need. In fact you should be able to get rid of the shim, and do it all with the rings.

 

[NateHaler]

Sounds like this barrel has been installed pointed significantly 'up'. Is it a pre-fit deal, or did you have somebody do the work? In the former case, I'd contact Lilja (after all, you're a repeat customer...)

If you paid somebody to do the work, then they should have a chance to address your concerns. Sounds like even if you had used a flat scope mount that you would be shooting high at 100y. Which isn't great, unless you never shoot at such short range.

 

[dieselten]

The problem is your new 40 moa total travel scope. As a general rule of thumb scopes are set up to be pointing dead straight (erector centered) at the center of their elevation travel. A 100 yard zero is only 1 or 2 moa away from a true straight line from your bore. If your bore is not straight, action threads not straight, scope base to receiver interface not straight,...all these things cause problems with exactly where the bore is pointing in relation to the scope.

40 moa total travel is not a lot and you will loose some of it if your windage is too far to one side. The erector only has total travel near the center for windage. Based on your description you would still be 4 moa high at 100 if you used a flat base. Problem is the bases might be slightly off, your 20 moa base might be 22 or 18 which only compounds the problem.

If you want to keep the 40 moa scope your best bet is to get a flat base and use Burris signature rings to center the windage and put in a little bit of cant (elevation), not a lot. You don't need a lot. A 6.5x284 only needs about 30 moa total (probably less) to get from 100-1000.

Now I will tell you my way to adjust the Burris rings. Get a Leupold magnetic bore sighter. Mount the flat base and new rings with "0" inserts. Zero at 100 yards (even if scope is bottomed out, don't worry). Mount the bore sighter and take a reading. Adjust scope windage to absolute center zero of erector travel and place elevation at approx. 5 moa from total bottom. Mount gun in a vise and remove ring tops. by changing inserts and pressing down on the scope to seat it in the rings and look through the scope at the bore sighter you can adjust everything to add maybe 10-15 moa in elevation and by twisting the inserts you can get some windage. Notice that twisting the insert for windage will also change the elevation. Just look through scope at bore sighter grid and get it where it needs to be. If you were way off at 100 on the original zero just add that difference back in now. When you get close put the ring tops on and tighten but still allow the scope to twist. You can now make final adjustments to windage with a small flat scewdriver on the edge of the insert if necessary. tighten it up and final check through scope at bore sighter to make sure nothing moved.

 

[BoydAllen]

If you put the reticle in the center of a test scope (or the one that you will be mounting) and mount it on the rifle with the 0 inserts, you can then take it to the range and shoot it at a known distance (50 yards works fine.) to determine how far off your bullet impact is from your point of aim. You will need both horizontal and vertical error, as close as you can get it. with that information and the center to center measurement of the rings, as they are mounted on your rifle, (front to back minus the width of one ring) you can calculate how much correction is needed by doing a couple of simple ratio problems. If you are up to the math, you can figure out what inserts to use and how they need to be rotated to move the point of impact in any relation to the point of impact that you want. To adjust a reticle to the actual center of a scope, I lay it in a pair of padded Vs and adjust it so that when it is rotated that the intersection of the cross hairs does not move, relative to a target, as the scope is rotated.

 

[apakesha]

Switch to a 0 Moa rail and it will solve your problem. I had the same problem when I had a 5.5 x 22 nightforce scope mounted on my rifle. It would sight in easily at 100 yds. When I changed to a 12 x 42 nightforce scope (higer magnification) I had the same problem you have. My point of impact was 20 inches below the target. I had to hold over 20 inches to hit the bullseye. I switched to a 0 MOA rail and it solved the problem. If you want to shoot out to 1000 yds you might want to use a 10 or 15 MOA rail to be able to sight it in at 100 and 1000 yds. The problem is with the higher magnification. With the higher magnification you lose field of view.
To verify this put your old scope on the rifle. I bet it sights in easily.

 

[BoydAllen]

If your point of impact was that much lower with an angled rail, could you have mounted it backwards? A proper mounting of an angled scope base would have the thicker part at the back, and with non elevation adjustable rings, the challenge might be getting the point of impact low enough for short ranges. What you seem to be reporting is the reverse, or did I misunderstand you?

 

[apakesha]

Boyd, You're right. I had to aim 20" low to get the bullet to hit the bullseye. On my rifle I use one piece rails for rem 700. You can only mount them one way. In any event, changing to a 0 MOA rail solved my problem. (Can't get anything past you).