Picatinny Rail out of Alignment

[rckendall]

I just mounted a new scope on a rifle and found that it took a lot of Left windage to get it to zero. So when I got home I checked both the scope that came off from it and the new scope and found that they both needed about 12 minutes left to zero.

With the new scope I still have around 18 minutes left remaining, but it just seems wrong to leave it like that. Are there any common fixes for this? I thought about trying to shim the rings, but that has it’s problems too. I also thought about posting this in the gunsmith section, but I will start here.

The picatinny is a NightForce steel with a lug and 8-40 screws and is pinned in place.

Thanks,
Richard

 

[Drop Port]

What action?

 

[ronemus]

Use Burris Signature Zee rings - the offset inserts will let you get close to zero at optical center. I also like the inserts because they grip well and won't mark the scope tube. No lapping needed because the inserts self align when assembled correctly. If you want a tactical look, the new Burris XTR Signature series is for you - 6-screw caps and built like a tank; I'm using them on my new builds because I have 34 mm tubes on my new scopes (Burris XTR II 8-40x50 FFP MOA) - the Signature Zees only go up to 30 mm. I've used the Signature Zees on 3 rifles with no problems whatsoever.

 

[KY_Windage]

Burris Signature Rings. They come with variable inserts that enable you to move the scope any direction you want up to a maximum of 40 moa. You only need 12.

 

[Clark]

12 years ago there was a missile research project [on the bench next to mine] for Fort Picatinny back East.
The scope used for alignment in the light lab was a Burris Signature on a Weaver rail.
The set up was shipped back and forth.
I thought it was funny we were sending them a Weaver rail.

 

[matman_eod]

Did you bed the rail which on receiver top with devcon? Slight bend of rail cause a clear deviation.

 

[MatthewsCarbineCo]

Is it mounted on Remington 700 Serial number prefix "RR" ? I had one just come through my shop with first hole near barrel shoulder on centerline and by the time you worked to last holenit was more than 1/2 hole off to left side of action

I just mounted a new scope on a rifle and found that it took a lot of Left windage to get it to zero. So when I got home I checked both the scope that came off from it and the new scope and found that they both needed about 12 minutes left to zero.

With the new scope I still have around 18 minutes left remaining, but it just seems wrong to leave it like that. Are there any common fixes for this? I thought about trying to shim the rings, but that has it’s problems too. I also thought about posting this in the gunsmith section, but I will start here.

The picatinny is a NightForce steel with a lug and 8-40 screws and is pinned in place.

Thanks,
Richard

 

[rckendall]

I don't have everything worked out yet, but I've been talking to my gunsmith about it. Since he enlarged the threads for the rail to 8-40, he thinks he probably trued everything to the action, and that possibly the barrel threads are off somewhat. He really wants me to send it to him so that he can pinpoint the problem. He now thinks that indexing off the barrel would be a better approach.

I am not ready to give up on fixing this myself and I have a plan in mind. I'll post results when I get them.

Thanks for all the help,
Richard

 

[Ackman]

For me, Burris Signature rings are the only way to go. And most of my rifels use the Zee version. What works for me when mounting a scope is to check ring (actually base) alignment with the action and barrel first, before clamping the scope iun there. I have an aluminum bar about 30" long, also a tube, both 1" dia. since most of my scopes are that size. With the ring bases clamped down and inserts popped in, just set the bar/tube in there and see if it's directly in line with the barrel. Should be directly over the muzzle. Real easy to tell if the base or bases aren't completely true and pointed in the right direction, not too uncommon. (Or even if the barrel isn't completely straight in the action, it can happen. Then there's another way to check that.) If the base(s) aren't exactly right it's much easier to get things aligned with Burris inserts before clamping the scope in there and fooling with scope adjustments. Doesn't take much misalignment to be way out at even 100yds,

 

[Ackman]

There's other ways of checking things too. Take two straightedges, I use 36'' long aluminum yardsticks, and hold one tight on each side of the rail. The muzzle should be centered between them. If not, the rail is probably off. I say it's "probable" until you check the barrel itself. Take the barreled action out and run very rigid straightedges along each side of the action. Check to see the barrel is centered. This is trickier because the action is round so both straightedges need to be centered on the radius. Helps to have another person. Another way is put the action against something flat, a table edge, a wall, etc. Do it on both sides, measuring distance to edge of barrel. Be sure the barrel is dead nuts true in the action. It's rare, but they can be off it happened to me, turned out to be a thick accessory recoil lug that was a few thou. out from being dead flat. Good luck finding your gremlin.

 

[rckendall]

Thanks everyone for your help. As I mentioned before my gunsmith wanted me to send it back to him, both to learn what the issue really was and then to fix it. I am pretty handy with fixing things but don't have all the precision tools or know-how to figure out where the problem really lies. I have a feeling it was the rings, as I found out switching the rings from front to rear made a difference.

But, I did fix it using my own shade tree methods. Originally I had used a set of precision rings that were not supposed to be lapped so I returned them and purchase a set of inexpensive ones and a lapping kit. I made a .010 shim to fit between the rail and the ring (it was like a tiny piece of angle iron), bonding it to the ring with Devcon Plastic steel. After curing I cleaned it up and began the lapping process.

It took a while and I progressed slowly, checking often to see the contact area. When I was satisfied with that, I installed everything back on the rifle and checked my work. At the range I bore sighted it and then shot on paper. In the end the scope is within 1-2 MOA of centered. I am really pleased with the results and I now have a lapping kit to use again if necessary. For me it is a win, win.

Richard