POI windage shift from 100-300 yards (2moa)

[Jonathan Zimmerman]

I have a rifle that when zeroed at 100 yards shoots 2 minutes right at 300 yards. I have been through a whole bunch of checks on this rifle, 2 scopes and 2 stocks with the same result. Tested in little or no wind multiple times. It is actually a really accurate rifle but bugs the crap out of me. I have ruled out anything to do with scope alignment since the scope will zero at 100 (close to center of scope). Any ideas for things to check would be appreciated, or what could cause this. It is a smokeless muzzleloader shooting 275's in an 18 twist Kreiger that's 22" long. I have heard of barrels not indexed properly, but can't see that being a problem either since I can get a good zero at 100. Thanks, Jonathan

 

[Larryh128]

My best guess is that the reticle is slightly canted. It will do that every time & it doesn't take much.

 

[Ggmac]

Another possible is that the orig scope base mounting screw holes are not on true TDC. At 300 does it continue to move POI to the Right ? Anothe possible , but usually not as noticable is certain weaver style rings on Picatinny bases or visa versa . It does the same as having the scope centerline offset . Have you always kept the rings oriented the same way ? Say for instance the rings have there clamping bar ( part that moves ) on the right side and the base is centered but the diff in weaver style compared to picat. Is .010 . The ring will tighten on the right side ( +/- ) because of the diff in styles . I hope I conveyed what would be easier for me to show you . The .010 is because Im to lazy to get up to get the actual specs . But they do make a diff . You can try just rotating your rings 180 , not front to back . You actuall need to change the side on wich the clamping bar is on.

 

[Jonathan Zimmerman]

Thanks for the info guys, I appreciate the help. I believe the reticle would have to be quite far off angularly to cause a shift this drastic. And it would be very noticeable. I have shot at 300 without adjusting my zero to check for this very problem. But, thanks for sharing your thoughts and trying to help Larry. I am curious about this other possible route cause, hadn't really thought of that. It is a nightforce 10 moa base. I was tempted to go as far as pulling the barrel, and installing another barrel to see if it is a sighting issue... One of these days I will figure it out. Thanks again for your help. Jonathan

 

[itchyTF]

If you move in closer than 100 yds, does the POI go left?

 

[Jonathan Zimmerman]

Yes it does.

 

[itchyTF]

Then I would venture to say you have an angular misalignment between bore and tapped receiver holes or base or rings.

 

[Jonathan Zimmerman]

Roger that, I will see what I can do to fix the issue. Thanks for the help guys. Jonathan