Question about a scope that was not boresighted correctly

[sleepyone]

I had a Buckmasters 3x9x40 scope mounted and laser bore sighted on my 336C by a gunsmith who I have used for years and has mounted several scopes in the past for me. This time something must have been off because it took me 40 clicks to the left and 40 down just to get it on paper. I was shooting at the center of a 4' x 2' silehoutte target at 100 yards and could not hit it. Once I got it on paper it took me another 20 down and ten left to get it where it should have been when I started.

I did some reading tonight to learn what is happening when a scope is adjusted for elevation and windage. The erector tube is what is moved during the zeroing process if I understood the article correctly, so my erector tube must be severely off center and at an extreme upward angle in relation to the reticle. I'm assuming the reticle is always stationary. Also, it is possible to break the erector spring with that much adjustment?

Has my scope been adjusted so much that I need to have it reset to factory settings and bore sighted again? Of course, I don't know how I would put it back to factory settings at this point. I did not make a note of the adjustments once I got it in the general area and I was changing bullet weights and having to make adjustments for those changes as well.

 

[BluegrassDan]

What kind if mounts are you using? Do the mounts have adjustable windage screws?

 

[Andrew Leigh]

You have 80MOA total adjustment which is +- 40MOA from center be it hortizontal or vertical. The scope adjusts in .25MOA steps so to return it to zero.

Turn each knob in the direction of the arrow / + sign on the knob taking care to count the clicks as this will tell you if the scope was indeed centered before you got it. Or if your current setting are close to centre.

When you run out of adjustment then write down the number of clicks and turn the knobs back in the opposite direction by 160 clicks (40MOA multiplied by 4 clicks per MOA).

Now take the number of clicks you counted in both planes and visualise these on a cross hair and this will tell you id you are off. If in fact correct you can simply dial back the old settings as you will know where you are.

 

[docsleepy]

So from Andrew's information, you are 60 clicks out of a possible 160 in the most extreme direction. (That's assuming the gunsmith left the scope in the default condition; he may not have.) I'd say you are still well within reason, just about 1/3 of the available correction utilized. If you want it better, and your mount doesn't have any adjustments, you could use some shims somewhere.

Assuming your rings are 4" apart, the shim is going to be in the range of .016" thick. You could try a piece cut from a soda can, or some .010 brass sheet metal.

But I would just zero the scope and go have fun! I don't shim until I have used up EVERY SINGLE BIT of the scope's adjustment (which has happened to me!)

 

[Ash]

Given it is a 336, I might be tempted to shim under the rear of the scope mount base. That would take care of much of the up/down centering. Left to right can't be done without a windage-adjustable base. But, if rounds are hitting where they should, the scope is working as it should.

 

[BluegrassDan]

I agree that if the rounds are on target don't worry about it. If it was a $3,000 ultra long range rig I might be more particular, but you're not going to notice any difference with a 336.

 

[David Clark]

Something is truely wrong. Being an old retired gunsmith and bore sighting 100,s of scopes if it was done right there is no way you could be that far off. Take it back to him and tell him what you had to do to get it sighted in. Now that you have it sighted in he can put his bore sighter back in it and see what it reads.
Dave

 

[jmr40]

Boresighting had nothing to do with the problem. As long as your scope is hitting where you aim all is good, but you shouldn't need to move it that much to get it zeoed, but then again 40 clicks at 100 yards is only 10". More than I'd like, but not horrible either. You should not have been missing a 4'X2' target if the scope was only off by 10".

You have 1 of 3 issues.

#1, the mounting holes on the rifle could be drilled incorrectly. This used to be fairly common especially when holes were not drilled at the factroy and were done afterward by a gunsmith. It is very rare with modern rifles that have been drilled at the factory. The fix is to use the windage adjustable mounts. They are designed to compensate for this problem and get your scope in line with the barrel before you make any internal adjustments. This is probably not the problem

#2, you may have scope mounts that are poorly made designed, or installed incorrectly. This where I'd look first. If you are using extremely high mounts, such as see-thru mounts, it can make for interesting zeroing since the scope is so high above the bore.

#3, the scope could be defective. Also a possibility

 

[madcratebuilder]

Was the scope at mechanical zero when installed?

I would avoid using any kind of shims, it's a good way to damage the scope. A set of Burris Zee rings with offset insert is the best way to move the scope body in the rings.

 

[sleepyone]

I am using Weaver high rings and a Weaver 63b base. I have always used Leupold rings and bases on my bolt actions but have read and was told that the Weaver setup is the most popular for 336s.

The scope is brand new. The rifle is a 2009 model; one of the last JM rifles made in New Haven.

Thanks for the info on getting it back to zero. Now that I have some knowledge of my own, I'm going back to the gun shop for unrelated business and will take the rifle with me to see what the smith says.

BTW, attached is my best group. It was real windy and I did not have any sandbags (the range had removed all the sandbags), so I was trying to make my range bag and tool bag work as shooting rests. Just about a two inch group.

 

[ball3006]

When sighting in a newly scoped rifle, start at a short range, 15-25 yards. That way if your scope is not alined with the bore, you still will probably hit the paper. Then adjust your azmuth accordingly, then your elevation. That way, when you increase your range, all you have to do is change your elevation as needed. I see it all the time where guys are trying to sight in their rifle at 100 yards and they don't hit the paper and they waste alot of ammo trying to when they don't have a clue where their rifle is shooting.

BTW, what caliber is your rifle? chris3

 

[sleepyone]

Here is what I have found on my scope using the method that a couple of you suggested. Keep in mind my rifle was zeroed at 100 yards yesterday after I was finally able to hit paper following a laser bore sight by the gunsmith.

I turned the windage knob all the way to the right until it reached the end of adjustment. That was 147 clicks.

I turned it back to the left until it reached end of adjustment. That was 373 clicks. This is my total windage range left to right.

I then turned it back to the right 226 clicks to get it back to where I started.

It appears the windage was not too far off center after I had zeroed it yesterday. Dead center with 373 clicks of total adjustment left to right would be 186.5, so 226 clicks for zero is not unreasonable.

I next turned the elevation knob all the way up until it reached end of adjustment, which was 179 clicks.

I then turned it down until end of adjustment was reached, which was 371 clicks. This is the total elevation range up to down.

I turned it back 192 clicks to get back to where I started.

Again, it appears the elevation was also not too far off center after I had zeroed it yesterday. Dead center with 371 clicks of total adjustment up to down would be 185.5, so 192 clicks for zero is pretty close.

Did I do this correctly? If so, I can only surmise that for me to have to do such a major adjustment to zero yesterday means that it not set to zero at the factory.

BTW, my rifle is .30-30.

 

[docsleepy]

Sounds fine, go enjoy it!

 

[Jackal]

I boresight by eye, down the bore at 50 yards. I'm usually not more than 4-6" off and sometimes I'm within an inch or two. Sounds like something was done wrong to me. However, none of that matters if you can get it on target within the scopes adjustment range.

 

[BluegrassDan]

Sounds like you're in good shape. Just be sure to shoot it again to be sure it hasn't drifted from where you last had it zeroed. Even with going the correct number of clicks, they sometimes don't land back where they started.

 

[sleepyone]

Sounds like you're in good shape. Just be sure to shoot it again to be sure it hasn't drifted from where you last had it zeroed. Even with going the correct number of clicks, they sometimes don't land back where they started.

No doubt! I'm sure I missed counting a click or two. After I had counted the total windage range at 373 and realized I was probably looking at the same with the elevation, I just started counting in groups of ten and making a tick mark on paper.

 

[ball3006]

I do what jackal does. Draw a line with a dot on the storage shed, clamp the rifle in a vise, aline the bore with the dot on the line, then look through the scope and adjust accordingly. Then go to the range and set up a 15-25 yard target and shoot to see where it hits. That way doesn't cost you anything....chris3