ring spacing or scope problem

[mudduck]

alright, I have nightforce nxs 5.5-22 mounted in harrell rings along with a 20 moa harrell pic/base on a 700rem in 6br. I mounted my 45x leupold com scope to shoot a score match but did not have enough down clicks to zero at 100yards. will ring spacing affect the internal adjustments on a base with built in moa or does this sound like a scope problem?

 

[Ggmac]

No

 

[Ggmac]

Base or I should say the leupold doesn't have the adj range the NF does .

 

[savagedasher]

No

I don't think it's a scope problem.
But the scope could have not moa built into it . My scope rings had too moa built and I couldn't get on at 100 . Ring hight can be a problem also . Larry

 

[Dave Berg]

The 20 MOA base will point the scope down 20 MOA or effectively point the barrel up 20 MOA. To get a 100 yard zero you need about 20 MOA of down from the vertical turret to offset the base slope. The Leupold 45X Competition only has 38 MOA of total vertical adjustment so if everything is perfectly centered, which it rarely is, the best you could hope for is 19 MOA up and down. That puts it still high at 100 when it's cranked all the way down. Your scope and base are probably working fine. Ring spacing does not effect POI with a tapered base. With Signature Zee rings spacing does effect POI but that's a whole different story.

 

[Ggmac]

Dats what I said , but you did a much better job !

 

[mudduck]

thanks guys , I was thinking the same thing.i thought the comp's had more Moa than that .Guess I'll buy some new lower rings for the Leupold

 

[Dave Berg]

Guess I'll buy some new lower rings for the Leupold

Lower rings will only help, again assuming everything is centered, by the difference in ring height. If you're currently two inches high at 100, going from high to medium rings will make it 1 3/4" high. If you switch to Signature Zee rings you can bring the POI down a few inches. But then rings spacing matters.

 

[BoydAllen]

Burris makes Signature series tactical rings, that take offset inserts, that fit Picatinny bases . Using those and the right inserts, installed in the correct manner, you should be able to undo some or all of the 20 MOA (a third of a degree) built into your base, which will solve your problem.

 

[hogan]

A Bushnell 74-3333 which is a spud boresighter with etched glass grid for reticle alignment or "collimation" could assist you. With this tool, you can be sure of scope concentricity with bore and set your approximate zero. I use .005 thick bronze or copper sheets, 2pcs 4"x6" to make shims. Trim the metal sheet to width of your base and use a small drill bit or center punch to locate your mounting holes in the shim. You might need 2 layers. Ordinary scissors will trim the sheeting just fine. The shim stock I used is available at hobby stores or maybe a decent hardware store...

The boresighter should be left undisturbed in barrel while completing your scopework. Count your total elevation & windage clicks, divide by 2 and you have your dead-center setting for scope. Your elevation reticle should super-impose with the boresighter grid's center line. The total grid area corresponds to 160moa at 100yds. The total area of the boresighter gives about 200moa to evaluate reticle movement. Usually, you reticle will locate 2-4 grids below the center gridlines when zeroed at 100yds. Once sure you are concentric you can use shims to set the reticle elevation where you want it.

In your situation, using a Harrell's 20moa base (a Picatinny rail or one-piece base?), you might change to Weaver bases and see where that puts your reticle on the boresighting grid. You will find that using the boresighting grid enables diagnosis of many problems and assures you of a good mount system.

While there is possibly some intrepidation at prospect of introducing any metal into your bore, the spud contact metal is not steel, nor does it produce enough tension to damage a CM or SS barrel's rifling. Not like you have to torque-down on the spud and achieve great tension. If you are stymied by a simple mounting situation like the one described, the 74-3333 or another tool like it could help you a lot.

 

[BoydAllen]

IMO one should never put one of those expanding spuds in the muzzle of a high grade barrel. All of this can be done by testing and calculation. Once you know how much change is needed at a known distance, it is all simple math.