Out of windage...where is my problem?

[gspn]

I have a long and continuing problem with a rifle. A few years ago I bought a Marlin bolt action .243 for my son (purchased new). I put a Bushnell Banner scope on top.

When I was mounting the base (one piece Weaver base), one of the four mounting screws sheared off. I had no time to deal with it at that time so I mounted the scope, zeroed it, and went on down the road. The rifle shot fine.

Fast forward a bit. The groups on this gun began to worsen. It might throw a 3 inch group at 100 yards (not acceptable to begin with), but a few groups later they blew out to 6 or 8 inches.

I tried different types of ammo...nothing worked. At that point I figured it might be a scope problem. I removed the Bushnell and put a Leupold on it. I took it to the range over the weekend and the gun was shooting WAY to the right. It was so far to the right that I had to walk up to 10 yards to get on the paper...and I was six inches right. I tried to bring the shot left but I very quickly ran out of windage. I couldn't adjust anywhere near enough to get to the center of the target.

Now I'm wondering if the scope mount could be the problem.

The Bushnell threw terrible groups that were centered on the target. The Leupold can't get close enough for me to even tell how it might shoot. If I back up to 20 yards it's off the paper and I can't bring it in.

Any ideas on what might be going on? I'm going to have to bring this to a gunsmith to have the sheared bolt removed and I guess I'll have to start over after that.

 

[Mosbyranger]

One possible issue is that the center axis of the scope is out of alignment with the bore. This could be compounded by repeated firing. That sheared screw in the base needs to be dealt with, nothing good can come of broken parts. Personally I would start by replacing the base and rings, true the scope, get it bore sighted and dial in at 25 yards. Then go to 100 yards and make the final adjustments.
MR

 

[Arkansas Paul]

Now I'm wondering if the scope mount could be the problem.

I would put money on it.

 

[scythefwd]

scope base.. get the shered off screw out of there, re D/T if need be. then re-mount. Now that you're back to right.. work on the windage issue. If your bases are out of alignment.. z rings by burris or millet angle locks.

 

[LAGS]

Once they fix that screw, then I would make sure the Scope is Reset to Zero by resetting the adjustments on a set of " V " blocks.
Then when the scope is set back in the rings, Bore sight it and " DO NOT " touch the adjustments.
That will tell you if your Mount or Rings are Scewed to your Bore, and make sure your Base and rings are tight.
Then " BEFORE" you do any monkeying with the scope adjustment knobs.
Try to Correct your cross hairs to center of bore by either Shimming the base or reversing one of the rings.
A laser bore sighter works best, but it can be done by removing the bolt and bore sighting it thru the bore at a target about 25 yards.

This all may seem like a lot of wasted time, and trouble, but it really is not if you want to get your rifle to shoot better, and still have as much adjustment on your scope adjusters.

Once you have Corrected as much of the "Base and Ring adjustment" that you can with the Scope Still set at Zero Adjustment.
THEN you can do the Fine tuning with your scope adjustment knobs.

If you sheared off a screw in your receiver, there may have been dirt or something in the bottom of the hole to start with.
Chances are, the other screws may also have something in the bottom, that is not letting the screws go down and tighten the base properly, even though the screws are tight.
Sometimes also, the factory screws are just one thread too long to allow for proper tightening of the base, and the screw can bottom out and sheer off.
The long screws will be tight in the receiver, but not holding the Base all the way down, it may feel tight, but it can still move under recoil.

 

[Outlaw Man]

^^^ This is exactly what I'd do.

 

[gspn]

Thanks to all...I now have a game plan.

 

[LAGS]

@ GSPN
Please do let us know what you ended up doing to your rifle.
Others do not know what works, or what doesn't if you don't give us any feedback.
There may be many that will come across similar issues and not have any idea where to start out to identify problems.

 

[gspn]

Will do...but it's going to be a while. i'm going to have to have the gunsmith remove that sheared screw and he takes FOREVER. I dropped a few guns off with him in September for some really easy work. He told me it would be a month...I still haven't heard from him.

I'll post again when I get it right...and I will get it right.

 

[Skylerbone]

Any LocTite used initially? I ask because so long as the threads didn't strip, you can likely remove the base and probably have some part of the screw still exposed proud of the receiver. Even if it's buried, you stand a good chance of removing it with a little ingenuity. Try a small piece of pencil eraser around a safety pin to back it out. Just cut a strip from a block eraser, insert the pin and shave it to fit the itty bitty hole.

I've resorted to medieval tactics on some older bedded installs and far milder tactics on simpler ones. I too would recommend a fresh base, no need to bother with the rings unless you sprung for a $2 set when you bought that Leupold. Intuition says no but I've been proven wrong before.

 

[LAGS]

@ GSPN
That is about right for gunsmith work. They want it for 6 weeks no matter how simple it is.
That is why my friends come over and have me help them on their guns.
And it Never fails, they show up on Friday Night, to get something fixed because they have a Match in the morning.
But they knew about the problem for a month since their last match.

If the screw broke off because it bottomed out in the hole or was too long, then the eraser trick wont work. but it is worth a try.
But pull your scope off and reset it to Zero/ Zero on a V block or use a small cardboard box with two V notches cut into it for a cradle.
And I would not condem the mount just yet, because I really feel the screws were too long, and that is why one sheared off, and the others may not be holding the base truely tight.
I have seen it 1000 times before because people think the screws for the base are made to fit every rifle and do not know how to check to see if they are one thread too long for THEIR rifle.

 

[gspn]

@ GSPN

And I would not condem the mount just yet, because I really feel the screws were too long, and that is why one sheared off, and the others may not be holding the base truely tight.
I have seen it 1000 times before because people think the screws for the base are made to fit every rifle and do not know how to check to see if they are one thread too long for THEIR rifle.

Dude I'm sure that's exactly what I did. It never occured to me to check screw length. I guess I should have used a micrometer to measure the depth of the holes and compared it to the screw length.

thanks a ton for all the help.

 

[Ro1911]

your shooting in a tornado or the scope needs to be remounted.