Rifle Scopes RPR Scope Mounting Trouble

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Guys,

Sorry for the rookie question here but I am surprised by the results I received so I am posting up.

I recent purchased a 6.5 CM RPR [Ruger Precision Rifle] and mounted a Vortex Razor Gen II 4.5 - 27 on top using Vortex Pro Series Cantilever 34mm Mount [CVP-34]

I know and see that the rail on the receiver is 20 MOA and the cantilever mount should be 0 MOA for a total angle of 20 MOA

I made sure everything was leveled and torqued properly and am not having issues of things moving so that isn't an issue.


I was doing an initial sight in at 100yd and after wasting a bit of ammo I realized that I had to come up 10 MILS. I was shooting Hornady Superformance 129gr SST that was given to me.

My issue is the 20 MOA base should put the bore ~ 20 inches above the line of sight at 100 yards

But with the 10 Mils low meaning i was ~36 inches low at 100 yards leads me to believe that something is up.

That would me i had about 56 MOA of error at 100 yds accounting for the ramp'd rail not accounting for bullet drop.


The issue is that i used 10/26 Mils of adjustment just getting to 100 yards.


Thoughts and things to look at and go over again?

Should i abandon the mount and get a different set of rings?

What gives, i am slightly lost here. I was just expecting to be closer than 10 Mils or shooting slightly high.


Thanks and sorry for the novel.

 

[BobinNC]

No, a 20 MOA base should put you 20 inches below line of a bore sight, not above. A Vortex 4.5-27x56mm has more than 26 MILS of adjustment. It actually has 33 Mils, but only 28.5 are usable because the turret is rev limited

 

[zblink]

Yes we are saying the same thing the minus's in the message above were supposed to be the squiggly about sign to the left of the number 1 on the keyboard.

So bore line is 20 MOA above, and i was shooting 10 Mils below (mounted on the 20 MOA rail) so it was about 56 MOA of error at 100yd which is my trouble.

 

[EXTREMEPREJUDICE]

Based on what you are saying I believe there are only a couple of possibilities. The first one is that the rail on top of your RPR receiver is installed backwards. Now I don't have a RPR and don't know if the rail could be installed backwards but that would be my first guess. If not, then someone replaced the 20 MOA rail with the aftermarket 0 MOA rail. I can't imagine it would be anything else?

 

[fdkay]

Is it possible that your mount is not fully seated? Did you mount it backwards?
Are you sure that the scope was at mechanical zero before you started?
Was it a new scope, did you buy used or take it off a different rifle?
I would check the mount, make sure there is no debris and make sure that it is seating correctly in the rail. Take the scope out of the rings and make sure they are clean and free of debris.
Next, I would return the scope to mechanical zero, remount and try again.

 

[FourT6and2]

When I zero a scope on a canted rail, I mechanically center the scope, then I dial DOWN 5.8 MIL to compensate for the canted base. Then I zero. Makes things easier in your head. Do this. Then report back if you're still experiencing issues.

So if your scope's turret reads 15 MIL when mechanically centered, Set it to 9.2 MIL before zeroing. Now your scope is mechanically centered to the rifle.


Ok, now to your issue. Possible culprits could include:

1. Something wrong with the rail
2. Something wrong with the mount
3. Something wrong with the scope
4. Something wrong with the barrel (bent or curved)
5. Something wrong with your process of zeroing

 

[lennyo3034]

Did you check how much elevation you have left after zeroing?

 

[zblink]

Ok I attached a picture of the setup.

Yes all brand new, scope, rifle, mount.

No the cantilever mount isn't backwards.
I figured the cantilever mount would have been a solid setup due to both rings needing to be machined together and it having a fairly large footprint on the rail.


I will have to wait until I get off of work to go through the mount to check seating, for debris, and the rings.

I will also set the scope back to mechanical zero and start over.

I will certainly check to see if the picatinny rail was installed backwards as it was installed when I received it. But it is labeled 20MOA on the rear like the attached picture. I can put a caliper on it to confirm.





Don't judge the crappy foam cutting, I did it in a hurry and only had a razor blade

 

[zblink]

Ok,

So i took off the rail, measured it. (0.60in on one end 0.65in on the other change in height of 0.05in) and it is 7.77 inches long.

That makes an angle of .369 deg
20MOA at 100 yards (3600 inches and 20 inches) is an angle of .318 deg
So my rail is just proud (over) of being 20 MOA


My remaining elevation available on the scope is 18 Mils which besides the huge POI error is one of the reasons I am complaining, but looking at drop charts i don't know if I should be or not. Just seems pointless to have that much adjustment wasted.

I reinstalled everything torqued it down and and used bubble levels to get everything at close to square as i could. The one picture that stood out to me is the forearm to barrel.

The rear of the receiver and forearm are both square to each other the rail is just off square but the forearm to barrel seems quite off. which is then not square to the rear of the receiver.

 

[Trigg]

The external contour of the barrel is not parallel with the bore axis. The slight taper of the barrel likely accounts for the discrepancy in the levels.

 

[zblink]

Ok I purchased a 20MOA mount so that should be my solution and bring me back up another 6 mils

I will post results when i can get back out and test it out.

Sorry for the rookie question

 

[BravoSierra]

I normally mount a scope first with a zero base and go to zero. Then I calculate how much cant on the base I need to get the most out of the scope before getting one. Depending on the load and what your discipline is, 16 Mils may very well be beyond the bullets capability.