Problems truing scopes for long distance shooting

[stagpanther]

OK--I know I'm out of my league posting this thread here--but I figure this is where the most experience with this kind of thing would be--so please indulge me--thank you.

I have quite a few rifles that I hope to one day use in a competition--once I'm up to it and have proper technique down. Many of my rifles I've been shooting for years with decent results though I haven't been getting out to any real meaningful distances. I want to change that--and have started off by buying Brian Litz's complete collection of books and DVD's and am presently absorbing that info.

I took four of my rifles (6mm Creedmoor, 6.5 Creedmoor, 300 win mag and 338 Lapua) and decided to true the scopes using the plumb line method. may not have used the right methodology--but using my dining room table I first leveled each rifle by putting a level on the rail. I have a plumb line hanging from a tree about 50 yds out in my front yard, getting up early at 5:00 am when things are still calm I sight each scope so the vertical line of the reticle matches the plumb line. I also added a bubble level to both the rail and the scope and leveled the bubble the scope while it was aligned to the plumb line.

So here's my problem: in every case on all rifles the reticles now cant strongly to the left (when leveling in the field using the bubble levels); I'm guessing by at least 5 degrees. I've been out shooting all the rifles, and in every case both my accuracy and precision have become worse--I'm going crazy trying to figure out the proper hold before firing. I knowBryan recommends the tall target test to check tracking and true of scope--but I seriously doubt I can learn to shoot well with the reticle canted to the side that much.

Any suggestions would be much appreciated.

[TXAZ]

I use a quality boresight laser from Sightmark, about $70.
To me it's much easier and more accurate than a plumbline, and is very easy to re-zero almost anywhere or time. I zero at 200 yards off a small reflector, which gets me on a target at that distance. Beyond that it's really just tweaking.

What do you consider "long" or meaningful distance?

[stagpanther]

How does a boresight assist in assuring the true of a scope? (asking cause I don't understand how that would work). thanks. Long or meaningful distance I would assume to be where tracking true becomes progressively more important--roughly 600 to 800 yds on out.

[tangolima]

In the house: Rail leveled. Reticle plumb.
In the field:. Rail leveled. Reticle cants to the left.

I can't see how it is possible. How did you know the reticle canted to the left in the field? You hung a plumb line next to your target?

I also true the reticle by eyeballing a plumb line. It works alright.

-TL

Sent from my SM-G930T using Tapatalk

[TXAZ]

Good question stagpanther.

First the boresight shows me where the bullet is going to hit (+/- 1-2") over a short (200 yards) distance. I neglected to mention I also have a level to ensure I don't have any cant in the aiming solution.
The intermediate step is to go out and shoot a group and note the impact vs. crosshairs.
Once I know the actual center of the test group, it's easy enough to adjust the zero on the scope to that point.

Does that make sense?

I've tried other methods. For me is the boresight is the easiest as its' where the bullet is going to hit within point blank range. Beyond that, it's just cranking mils vs. distance into the scope based on Shooter (the ballistic app).

[stagpanther]

I can't see how it is possible. How did you know the reticle canted to the left in the field? You hung a plumb line next to your target?

I know--I'm wondering the same thing. The whole reason I put the bubble levels on is because I usually don't have a level surface shooting in the field. I have one on the rail--and one on the scope, and they agree with each other on the angle of cant. I cant the rifle on the rests until both bubble levels are centered--and looking through the reticle it's obvious there is a cant to the left in the reticle. My conclusion is that there is a flaw in my methodology--I just don't know what it is--and I'm all ears to hear a better one.

One thing I thought of--as unlikely as it might be--since I'm sighting in through a window to the plumb line outside--can that create some kind of visual distortion that could throw the results?

Once the sun comes up--there is no such thing as calm here on the coast--winds are almost always blowing, pretty strongly at that, which is why hanging a line next to the target doesn't work--though I may try a "tall board" and use a carpenter's level to check it's plumb.

[stagpanther]

First the boresight shows me where the bullet is going to hit (+/- 1-2") over a short (200 yards) distance. I neglected to mention I also have a level to ensure I don't have any cant in the aiming solution.
The intermediate step is to go out and shoot a group and note the impact vs. crosshairs.
Once I know the actual center of the test group, it's easy enough to adjust the zero on the scope to that point.

Does that make sense?

Yes it does make sense--and is usually what I do--at least up until now. I'm a bit stumped as to optically why it appears to be a disconnect between what the levels are showing and what the reticle is showing. I'm assuming I made a "rookie mistake" and was hoping it was something other people have run into--and thus an obvious solution (other than I'm crazy, I already know that).

[TXAZ]

Stagpanther,
With multiple rifles it's not as likely it's each of the scopes, but more likely a common denominator in your methodology (unless when aligning the scopes you introduced a consistent error in the mounting).

[stagpanther]

With multiple rifles it's not as likely it's each of the scopes, but more likely a common denominator in your methodology (unless when aligning the scopes you introduced a consistent error in the mounting).

Exactly--since the same error was repeated with each scope.

[HiBC]

A plumb line cannot help but be calibrated to gravity.And disregarding wind,etc, the gravity fall line is the path of bullet drop.

Orienting the reticle and adjustment axis (W+E) to a plumb line is as good as it gets.

Laying a bubble level across the rail...Assumes no error from the bubble level,
Not all bubble levels are created equal. What happens when you turn the level 180 deg and set it back on the rail
I assume we are talking picatinny rail? The actual orientation comes from the 45 deg edges of the rails.Thats what the rings clamp to.


Al of which is sort of a distraction. You can use that flat top square your rifle in the vise pretty close. Set your scope reticle to the plumb line.

All good....BUT!

What calibrates the bubble level on your scope to the plumb line?


While the reticle is on the plum line,you have to calibrate the bubble on your scope dead nuts level.


Also,parallax is not just a scope term.It comes into play ,for example,reading instuments like an analogue Volt Ohm Meter with a needle sweeping a scale. That's why they invented mirror scales.


You will get an error if you look at the screen from an angle other than straight on. The needle and the scale are not on the same plane.


If your right eye is looking at the scope reticle and your left eye observes the scope level,your view through the graduations on the glass vial is offset from the bubble in the vial.

You have to calibrate the scope level bubble to the plumb line with your eyes in the same point of view as when shooting

[stagpanther]

Thanks HiBC--that gives me some new ideas of what to check for; I'm going to start all over again. Do you think sighting in through a window might induce some error as well? The only reason I do it from inside is that we still have a couple feet of snow and ice on the ground--the going's tough outside until maybe mid-April.

[HiBC]

A couple other examples of the error I'm trying to point out.

A classroom.Desks in rows. Clock centered on the front wall.

Teacher says "When I say "Go".from your desk,write down the exact tme"

On "Go",the kids in the center row of desks write down 12:00

The student in the front desk of the far left row writes 12"03,and the student in the front desk of the far rgt row writes 11:57.Why?

In a car with the sweeping needle speedometer,does the drver read the same speed as the front passenger?

The same idea even applies to shooting right handed with a left master eye.

In the field,looking from the side with your left eye,your scope level shows error.You can correct it by adjusting your scope level to your left eye in shooting position.

Sighting in through a window?My smart alec question,doesn;t that break th glass?

I'm not an otics engineer.,but does a glass lense or a prism bend light?

If you stick a broom handle in the water,does it look bent?

I use an indoor lumb line,contrasted against a white wall. Plumb line does not need to be outside.All the level calibration can be done indoors without windows.

[tangolima]

The reticle was obviously canted to the left in the field. So it just appeared canted. You need something equivalent to a plumb line to be sure. Human perception can play trick on you sometimes.

-TL

Sent from my SM-G930T using Tapatalk

[stagpanther]

Human perception can play trick on you sometimes.

That's what I worry about, I already have bad eyesight, and people that know me well would probably say there's more than a few marbles missing from my collection.

Great advice and pointers HiBC--thanks! In regards to doing everything indoors--I was under the impression that a distance of 50 to 100 yds would be better to true since you could run up and down the magnification and elevation settings

[HiBC]

I assme the op is using one of these in the field,with a calibration issue.

If the op is not using one of these, and is simply canting the rifle,well,thats why they make these scope levels.Spirit level sights have been around a long time.The old BPCR shooters used them with the tall Vernier rear sights,sometimes incorporated in the front sight,sometimes in the barrel sight dovetail.

I get it that if a person was not thinking in terms of one of these,my comments would be very difficult to follow.

https://www.sinclairintl.com/optics/...prod58649.aspx

[tango1niner]

How about aligning the scope with the bolt lug ways and get the rail right out of the picture completely? Perhaps that is where the error is coming from. How accurate is the level as not all are created equal as others have said.

[LineStretcher]

At first I was wondering what type of rifle you were sighting in but then you said it was happening to all 4 rifles so that became moot point. I then had to wonder what single factor would affect all of them the same and the only thing that makes any sense is that you're trying to do this through a glass window. It's probably double pane and nitrogen filled so who knows what kind of distortion you're getting from that but for sure there is some unless your window glass is made by Schott. Really, it's the only external factor that's common to all of your rifles.

So, I didn't say all that without having a solution in mind and here it is.

1. Position your rifle so that one of your walls is about 5-10 feet from the ocular lens.

2. Turn out the lights and point a strong flash light into the objective lens. Now look at the wall. You should have a silhouette of your reticle on the wall.

3. Hang your plumb line on the wall, level your rifle, loosen your rings and adjust your scope so the reticles vertical lines, align with the weighted string.

You can adjust your power settings to make the silhouette sharper if needed. You are not aligning your scope with your bore at this point, you are just making sure that it is trued to a known level point on the rifle.

To get it on paper, just put a piece of paper on the wall with a black dot on it and then remove the bolt and look down the bore and put the dot in the middle of the bore. Now measure the distance from center of bore to center of the scope objective lens and then put a second dot on the paper that is the measured distance above the first dot.

Now look through your scope and adjust your windage and elevation to align the cross hairs with the upper dot.

I guarantee you will be on the paper and you should only need two shots to sight it in.

See, sometimes there really is a easy solution.

[stagpanther]

Nifty suggestions line stretcher--thanks for that. I think I actually saw the light through the objective thing suggested, I think it was on sniper's hide, when I did a google for more info.

[stagpanther]

Ummmm...time for a public DUH--in my haste to shoot my new savage 338 Lapua--I neglected to check the rail attachment to the receiver (I assumed it would've been torqued down and loktited correctly)--and it's loose. Time to degrease and reattach.

Went out briefly today (about to start snowing, winds 22+) and tried again with the 300 win mag--things got a bit complicated--upon recoil the scope level's bubble would split in two forming two unequal sized bubbles.

[stagpanther]

linestretcher I just used your suggested technique and it seems to work quite well--I was a bit surprised to see that the true that I had previously set using the outside plumb line was almost dead-on with the light-through-objective technique (I was also careful to make sure the rifle was square and level in all the axese to the plumb line) . I already have pretty poor eyesight--but I'm beginning to worry that something may have "snapped" (in me) during that session when seemingly out of the blue everything started looking canted and I started shooting wide.

[LineStretcher]

It's possible that you suffered a mild concussion. Typically it will feel like a dull headache that subsides in a few minutes and it can affect vision. I get them if I shoot my big guns and just use ear plugs. If I wear plugs and muffs I don't seem to get them.

[stagpanther]

Getting old sucks.

[RC20]

No, its great, we can be cranky and no one can take offense. In our case almost no taxes on the house now, wheeeeeee. All those people that vote for those stuipd curb and gutter bonds pay for it not me. And then there is Medicare.

That's what I worry about, I already have bad eyesight, and people that know me well would probably say there's more than a few marbles missing from my collection

No worries, if we find them we will PM for an address to return them to.

[stagpanther]

[banginsteel]

What I normally do: after scope is set on the rifle with rings loose around the scope. Clamp the rifle in a bench vise, put a bubble level on the rifle rail and level rifle, clamp the rifle down so it's very snug, 6 to 15 feet away on a wall hang a plumb bob or use a good level and draw a line on the wall, dim the lighting and shine a bright flashlight thru the scope from the objective end, this will cast your cross hairs onto the wall with the line or plumb bob, adjust your cross hairs accordingly, as you tighten the scope rings watch carefully that the rifle bubble level and scope cross hairs do not move. The above is assuming you have your eye relief for the scope set and other obvious things completed.
This should help eliminate your wind problem and prizm issue looking through glass. I hope this helps. I always do the tall target test after this to confirm scope and bore are true.