Aligning scope base with bore

[Ledd Slinger]

Just looking for some insight on methods used to center a one piece scope base to center of bore.

Have an old 722 action I bought and the alignment is causing me to max out windage and elevation.

Plan on bedding the base once aligned properly.

Not interested in Burris Signature Zee ring solutions. That would be a last resort.

 

[Gundoktr]

Bed the rings instead!

 

[Ledd Slinger]

Bed the rings instead!

I usually do that as well, but in this case, the base is so far off that I would like to have it somewhat close. Wouldn't want to try and bed that much windage into the rings.

 

[jrm850]

Assuming a scope with 15 minutes of travel from center is maxed out, one set of base holes would have to be off center by roughly .025". A lot.
You could open the base screws to 8-40 which would not be easy because you would have to split the .025 offset distance in order to remove all of the old 6 threads.
You would have to mill the holes also.

With that being said, my guess is that it is more than likely your barrel.

 

[Ledd Slinger]

See, it could be the base or the scope. I'm looking for methods to 'check' the alignment with the barrel.

Don't think it's the barrel, just had a custom Shilen Match ratchet rifle barrel put on and action has been trued in every way. I was able to get it on paper and the thing is a tack driver.

 

[jrm850]

See, it could be the base or the scope. I'm looking for methods to 'check' the alignment with the barrel.

Don't think it's the barrel, just had a custom Shilen Match ratchet rifle barrel put on and action has been trued in every way. I was able to get it on paper and the thing is a tack driver.

Ah, I misunderstood. Sorry about that.

I would put the action in the mill vice and run an indicator along the side of the bolt and then again along the side of the base to see the difference. Use whatever bar he used to true the action if you want to be more precise. What kind of scope are you using?

 

[Ledd Slinger]

The scope is just a cheapo Shooters Choice 8-32x50. It's nothing great. That's why it is a suspect in this trial. I keep it around to put on rifles for barrel break in and 100 yard load testing. Can't remember if it took a lot of adjustment on other rifles.....

 

[kawzak]

You may or may not want to use these, but I have and I like them. Leupold standard bases have rear "windage" screws that move the rear set of rings side ways as you want, then lock down. I make sure scope adjustments are in the center, then move the scope with the base windage screws. final settings are done with the scope adjustments. that way you can start off as close to the center of adjustment as possible. I am not a professional shooter though. I have never heard any having problems with them. If your using a big/heavy 300mm scope-you could go up one size and tap the base screws out to 8-40's. IMO.

 

[Ledd Slinger]

Lay a three foot long straight edge tight against the action parallel with the barrel. Measure the gap between the straight edge and the barrel. Now do the same with the other side. If they are the same it is the scope base screw holes are out of alignment. If they are different then the action threads were not single point cut but a tap was used to chase the threads. Ask me how I know. My ex-smith said the Tap was good enough for the Rem. action threads. Me in my ignorance at the time believed him and went with the excuse that scope mount screw holes were crooked. Had that same action true up for a new bolt, single point threaded and lugs cut and VIOLA the barrel was straight with the action when I rebarreled it. Randy

I figured it out. Funny you mentioned using a strait egde because that's exactly what I did. I used my 4 ft aluminum framing level and laid up up against the side of the scope base and measures to the barrel. Ended up being a combination of things.

First, the very front base mounting hole on the action was off a little. Second, I had not lapped my rings yet and they made things even worse. So I left that front screw out of the base and lapped the heck out of the rings. Then I bedded the rings with JB Weld for a 20 MOA adjustment. A quick bore sighting at 50 yards showed elevation was now corrected and windage was nearly perfect.

 

[Dans40X]

Indicating screw hole locations to center line would render reference numbers & eliminated assumptions,compared to a yardstick measurement.

 

[Ledd Slinger]

Indicating screw hole locations to center line would render reference numbers & eliminated assumptions,compared to a yardstick measurement.

Good point. I'll remember that if I run into this problem again. Thank you.