Rifle Scopes Ran Out of Adjustment...What Do I Do?

P

principlecaliber

Private
Minuteman
Dec 18, 2018
18
13
#1
I have an SWFA SS 16x42 mounted on a Nightforce Unimount 1.125 with 20 MOA taper. The optic has 40 Mils of elevation and the base adds about 5 Mils, so I should have 45 Mils of total adjustment.

I went to shoot today and push my limits. I setup at 1667 Yards which called for 32.47 Mils. I could only get 14 Mils of adjustment before it was topped out. I checked Nightforces website to ensure my mount was installed the correct way, and measured the distance from the optic to the rail in back and front of the optic, so it's mounted correctly. Just looking at the adjustment post when it's at zero, it's already adjusted way up, over 20 Mils.

I have no idea what's going on. I should be able to push this setup beyond the rifles capabilities.
 
#3
You're only going to get about half on the total adjustment. plus what ever your unimount will give you. But it sounds like you have it mounted backwards, you should at the very least be getting around 25 Mils of adjustment.
 
#4
The SWFA site lists the 16x42 as having 30 mil total elevation.
My 16x42 mil-quad has 17 mils (plus a couple tenths) from a 100 yard zero to top out on a 0 MOA base on my old savage AXIS.
For references, it's zero'ed right on the number "4" on the scale under the elevation turret.
With a 20 MOA mount, you should be getting more.
 
#5
So it looks like the total Mil adjustment is 32 Mils. I just checked the mount again. It's installed correctly. I remeasured. It sits higher in the back. So the mount is good to go. I get 17.4 Mils adjustment down, and 14.6 Mils adjustment up. Idk what I'm missing.
 

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#6
Covertnoob5 said:
Does that optic have 40 mils total? Cause then it’s 20 up and 20 down. I’m not sure I know of too many scopes that have 40 mils of up. Even my ZCO only has 36 mils of up.
Click to expand...

So it's actually got 32 Mils, just from adjusting throughout it's full range of adjustment. So 16 Up 16 Down. But from my zero it's got 14.6 Up and 17.4 Down. I can holdover 10 additional Mils. But with the base, shouldn't it have more up than down? Do I need to zero this at 200 Yards?
 
#9
Precision Underground said:
Something is off if you only have 14 mils up with a 20 moa rail. Gas block touching handguard and pressing barrel down maybe?
Click to expand...

It used to, I switched to a set screw gas block and used a simple jig. 100% clearance all around now. I know, I have more downward adjustment than I do up. I don't want to just switch my scope to fix the problem. Ill try any suggestions.
 
#10
principlecaliber said:
It used to, I switched to a set screw gas block and used a simple jig. 100% clearance all around now. I know, I have more downward adjustment than I do up. I don't want to just switch my scope to fix the problem. Ill try any suggestions.
Click to expand...
I would not suspect the scope to be the issue. Something is making the rifle shoot lower than it should.
 
#12
Who chambered the barrel?
What barrel blank was used?

I suspect the barrel ended up with the slight curvature of bore that is present in all barrels being at bottom dead center. That'll eat up your elevation quickly.
 
#14
I would remove everything and reinstall it. Makings sure all surfaces are clean and smooth. Maybe center the scope a little more in the rings, it looks like it might be touching the bell in the back.

I usually try to eliminate my user error before suspecting equipment defects.
 
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#16
How is swfa support? Wouldnt hurt to give them a call.

I learned my Burris XTR reticle is designed off center and is already compensated for a 20moa rail when I called them with a similar issue.
 
#18
Precision Underground said:
I would not suspect the scope to be the issue. Something is making the rifle shoot lower than it should.
Click to expand...
So I looked into it once again per some of the comments here. It looks like SLR Rifleworks gas block has a screw on the side that allows the gas block to "click" to different positions. This screw is contacting the rail, which is also from SLR Rifleworks. The barrel is also not centered in the rail itself. It's low, and off to one side. I'm assuming this can make a huge difference although I don't know if it's the barrel, or the barrel and the rail.
 
#19
How many moa or mil do you think its off or is missing?

The above doesnt sound good. I would definately investigate why things are off center.

Though i cant imagine a touching gas block would cause more than a 1 moa shift.
 
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#20
2aBaCa said:
How many moa or mil do you think its off or is missing?

The above doesnt sound good. I would definately investigate why things are off center.

Though i cant imagine a touching gas block would cause more than a 1 moa shift.
Click to expand...
Yea its way off. I have the same exact build in an AR15 platform. Same scope, same mount, same rail, zeroed at the same distance, and that optic has 26Mils of adjustment Up from zero. This one has 14 Mils. So I'm missing about 12 Mils.
 
#25
principlecaliber said:
So I looked into it once again per some of the comments here. It looks like SLR Rifleworks gas block has a screw on the side that allows the gas block to "click" to different positions. This screw is contacting the rail, which is also from SLR Rifleworks. The barrel is also not centered in the rail itself. It's low, and off to one side. I'm assuming this can make a huge difference although I don't know if it's the barrel, or the barrel and the rail.
Click to expand...
I guessed in my first post that gas block was pushing barrel down. What did I win?
 
#26
Is your windage centered or near center? If your windage is left or right to achieve zero (which can be caused by a crooked base or rings that are not even) then your elevation will be reduced as the erector is moving up and down in a smaller arc. Your max elevation only occurs when the erector is centered for windage.

Cheers,

Sirhr
 
#28
sirhrmechanic said:
Is your windage centered or near center? If your windage is left or right to achieve zero (which can be caused by a crooked base or rings that are not even) then your elevation will be reduced as the erector is moving up and down in a smaller arc. Your max elevation only occurs when the erector is centered for windage.

Cheers,

Sirhr
Click to expand...

I just verified total travel on windage, it's 32 Mils. I'm sitting 1.3 Mils off dead center. I have 14.7 Mils R, and 17.3 Mils L. Is that close enough to center to give the erector full ROM?
 
#30
Like I said earlier, I would remove the scope and rings inspect it and re-install putting the scope centered in the rings.

If that didn't help, I'd remove the handguard and barrel inspect it and re-install.

If it was still off i would call swfa support and pick their brain.

Good luck, Keep us updated on what you find.
 
#31
principlecaliber said:
I just verified total travel on windage, it's 32 Mils. I'm sitting 1.3 Mils off dead center. I have 14.7 Mils R, and 17.3 Mils L. Is that close enough to center to give the erector full ROM?
Click to expand...


In theory you will lose a tiny bit of elevation travel. But not enough to matter or cause the large numbers you are talking about.

Strike that off the list of possible causes!

Cheers, Sirhr
 
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#32
principlecaliber said:
Credibility, respect and gratitude lol.
Click to expand...
Take the handguard off and shoot at your zero distance. If they print high you know that was your issue. If you can see the gas block touching hopefully it’s just the gas block pushing the barrel down and not the barrel warping down.

As long as you can count the mils in elevation and there are enough of them the scope is likely not the issue. The fact that you can visibly see the barrel is favoring low in the handguard tells me that is your issue. Question is- is the barrel bent or is the gas block pushing it down.
 
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