Leveling your scope

[davewilson]

Kevin Cram said; How do we know the bore is cut exactly through the center and not off the one side. If you put centers in each end of a barrel and spin the barrel in a lathe you will see that alot of barrels run out of round from bore to outside.

i was at Bruce Baer's and he was putting a brake on a factory gun. it was spinning in the lathe and i couldn't believe how much the chamber end was bouncing up and down. more than an 1/8th of an inch. with production barrels, i think this is not uncommon. with the better aftermarket barrels that are used by the majority on this site, i think the bore is within .005 of the center of the barrel. the better smiths keep the chamber and barrel threads within .001 of the center of the bore.

you're the smith here, are these numbers in the ballpark?

 

[woods]

I agree that having the reticle level is the only important thing when shooting. For me before I got the EXD device I would level the reticle by repeatedly throwing the rifle up and checking to see if it looks level. It is extremely irritating to bench the gun at the range and realize that the scope needs to be rotated. Since using the EXD I have not had that feeling that the reticle was just a little off.

I have also tried the level-level-level both in the action like on this Mato

and on the integral scope bases like on this Sako

and have no confidence in the reliablilty of those small levels, the scope bases or the top turret of the scope.

Now that is of course my opinion and not meant to say that I believe that they don't have some value, just that IMO the EXD is much more of an exact and well made instrument than the other method

As far as why worry about holding a rifle without cant, I would say why not? I have installed 6 scopes on friend's rifles in the last 6 months and all have asked how I could get the reticle so level. When the scope is aligned with the bore then it is right and not subject to how I might hold the rifle different than someone else. It is in the middle of the range of how shooters hold a rifle and ALL can adapt their shooting to hold the reticle where it seems level.

Only $40.00!

 

[HUAINAMACHERO]

Thank you guys for the replies. I have learned a lot on what you all added and explained. But all these techniques and equipment got me to a new question: after leveling the scope the final test should be shooting at a given distance, then cranking the scope up and shooting again, and cranking the scope down and shooting again, and all the shoots should be in the same vertical line?

 

[MontanaRifleman]

The shooting plain of the rifle and the sight plain of the scope must be in concert (parrallel left nad right). If they aren't, it will cause the bullet to drift left or right past the zero point. The scope must be plummed to a plumb reciecer. If it isn't the shooting plain and the sight plain are not syncronized.

IMO the best way to do that is as folows...

The last scope I bought, the dealer put it on for me although I would have done it myself. I'm glad he did, because I watched and learned how to do it accurately. He used loctite on all the screws. Here's what he did.

1) placed the rifle in a rest and put a small magnetic level on the receiver's scope base and leveed it, right - left, not front - back..
2) put a level glued to a small round magnet on the muzzle and level that level to the one on the receiver.
3) removed the level from the reciever and attached the bases and bottom ring halves, using loctite.
4) placed the scope in the bottom ring halves, and attached the top halves of the rings, but not tight.
5) took the rifle and gave it to me to hold to adjust scope forward/backward to fit my eye relief. Need to be careful here, that the level on the muzzle is not disturbed.
6) put the rifle back in the rest and leveled it usine the level attached magmetically to the muzzle.
7) took the level used to level the receiver and put it on the top turret of the scope and leveled the scope in the rings, then double checked the muzzle level again.
8) tightened down the ring screws incrementally. Good to go.

A good way to double check this is to align your verticle reticle on a verticle line some distance away, the farther the better, then look down your bore with bolt removed and see if the distant verticle line bisects your bore.

My $.03

 

[MontanaRifleman]

Thank you guys for the replies. I have learned a lot on what you all added and explained. But all these techniques and equipment got me to a new question: after leveling the scope the final test should be shooting at a given distance, then cranking the scope up and shooting again, and cranking the scope down and shooting again, and all the shoots should be in the same vertical line?

Yes, but I think a better test would be to fire at different ranges with and without changing your elevation and look for the same verticle alignment.

 

[mattj]

The shooting plain of the rifle and the sight plain of the scope must be in concert (parrallel left nad right). If they aren't, it will cause the bullet to drift left or right past the zero point. The scope must be plummed to a plumb reciecer. If it isn't the shooting plain and the sight plain are not syncronized.

I'm pretty certain that is not correct (and maybe a true optics guru can jump in here and explain it better than I can)... but when you sight in the scope (and use proper parallax adjustment) on the horizontal axis, you are making an angular adjustment to the horizontal sight plane so that it is parallel to the horizontal barrel plane. By dialing the scope in you ARE syncronizing the sight and shooting planes.

As long as you can dial the scope enough to get the reticle "sighted in" (and still have the adjustment range you need to dial windage), the "plumbness" to the bore axis really doesn't matter.

Now what you can't correct for is horizontal offset -- but its effect is so miniscule compared to the angular factors that it becomes insignificant.

-Matt

 

[mattj]

MontanaRifleman,

On first reading, I originally thought you meant angular alignment of the scope, on re-reading, I think you may be referring to the rotation of the reticle -- I'm not sure which you meant.

If you were indeed referring to the 'rotation' of the reticle -- then refer to my previous post in the thread--- the alignment does indeed matter, but it's the relationship to gravity that is important, not so much to the action.

-Matt

 

[MontanaRifleman]

After rereading my post, I probably should have sai it this way... The vertcile (windage) reticle needs to be plumbed with the reciever (bore). If the scope is canted in anyway, the bullet will drift left or right, *if elevation adjustments are made*, depending on how it's canted when fired closer or farther than zero distance.

When you make windage adjustments to fine tune the zero, it should be aligning the reticle with the center of the bore, with the reticle being verticle to the bore, and this is assuming the receiver mounts (holes) are correctly centered to align center of scope with center of bore.

If your reticle is canted, let's say to the left in relation to the bore, then when an elevation adjustment correcting for drop is made, your scope POA moves left, and conversly the line of your bore moves right as you put the cross hairs on target. So... the scope reticle must be "plumbed" to the bore of the scope.

 

[Mikecr]

The only way to know how the reticle moves with adustment is to shoot the gun through the scopes range. Some shoot NF dots, and use no crosshair at all.
Doesn't matter..

If you adjust your scopes elevation in the field, that adustment is what matters, and not a reticle plumb. Turret adjustment plumb.
For this case:
Using a scope level(set true to the gun, or true to shooting cant), shoot in the field in 10moa increments till your scopes out of elevation. If your shots are not walking a plumb line, turn the scope, and repeat till it's right. If you find that after this your crosshair seems crooked, who cares?

 

[mattj]

After rereading my post, I probably should have sai it this way... The vertcile (windage) reticle needs to be plumbed with the reciever (bore). If the scope is canted in anyway, the bullet will drift left or right, *if elevation adjustments are made*, depending on how it's canted when fired closer or farther than zero distance.

When you make windage adjustments to fine tune the zero, it should be aligning the reticle with the center of the bore, with the reticle being verticle to the bore, and this is assuming the receiver mounts (holes) are correctly centered to align center of scope with center of bore.

If your reticle is canted, let's say to the left in relation to the bore, then when an elevation adjustment correcting for drop is made, your scope POA moves left, and conversly the line of your bore moves right as you put the cross hairs on target. So... the scope reticle must be "plumbed" to the bore of the scope.

I'm with you now -- my clarification of that though would be that the important thing to be level to is not the action/bore, but instead gravity-- ie your scope can be canted with respect to your action, but as long as you get the reticle level with respect to gravity each time you shoot, you will not have the problem you describe (only a very tiny amount of horizontal offset, which won't be noticeable on target). Likewise, your reticle can be absolutely perfectly plumb with your action/bore, but if you cant the whole rifle with respect to gravity when you shoot (which is very easy to do without realizing it), you will have that problem...

So my point is that it is far more important to have an anti-cant device set up to tell you when your reticle is level with respect to gravity than it is to worry about being perfectly plumb with the action --- hence I don't concern myself all that much with getting the scope *perfectly* canted in the rings (I do my best to get it as close as I can without special tools), but am very careful about setting up my anti-cant device so that I my reticle gets aligned to gravity for every shot.

-Matt

 

[dmgreene]

I believe the best way to make sure every thing is right is to shoot the rifle. I eyeball the reticle and get as close as possible and then zero the rifle at 100 yards. Then use a target with a vertical line that is at least 24 inches high with an aiming point at the bottom of the vertical line. Use a plumb bob and make sure the line on the target is perfectly plumb. Make sure the rifle is level and fire the first group at the aiming point which is on the line at the bottom of the target. Next dial in 20 moa or so of elevation. Reaffirm that the rifle is still level and fire at the same aiming point as before. If the group stays on the vertical line then you are good to go. If the group is to the left or the right of the line then you need to rotate the scope and try again until the scope tracks straight up and down the line. Sometimes the reticle can be canted inside the scope and you need to make sure the vertical travel alignment is correct more so than the reticle being level. They should be exactly the same but sometimes they can be off a little.

David

 

[Broz]

Dmgreene , That sounds like a good way to get it right. After you do this do you then check and re-adjust at a longer range? Like 500 yds as long as it is calm and no wind?

Also it would seem a pencil line on the tube of the scope, matched to the parting line on the bottom scope ring would be nice to use as refrence point. then wiped away after you are done.


Jeff

 

[MontanaRifleman]

I'm with you now -- my clarification of that though would be that the important thing to be level to is not the action/bore, but instead gravity-- ie your scope can be canted with respect to your action, but as long as you get the reticle level with respect to gravity each time you shoot, you will not have the problem you describe (only a very tiny amount of horizontal offset, which won't be noticeable on target). Likewise, your reticle can be absolutely perfectly plumb with your action/bore, but if you cant the whole rifle with respect to gravity when you shoot (which is very easy to do without realizing it), you will have that problem...

Maybe I'm missing something here but it sounds like you're saying two different things. Yep, gravity is the key ingredient here. I think a good way to look at this is to use the bullets path to define a plain in a calm, no-wind situation. The bullet will start to arc immediately upon leaving the bore. The plain defined by that arc will be perfectly verticle (plumb) and inline with the bore. In order to predict the no-wind path of the bullet with our scope we need to align the verticle reticle with that plain which is aligned with the bore/receiver, so everything is in line with the force of gravity (plumb). If the reciever is not aligned (canted) with the scope reticle, the bore has to be aimed across the scope plain to intersect at zero point, and past zero point the bullet departs the line of aim of the scope. It would be a lot easier if I could draw this out. When shooting at short ranges this isn't all that critical, but the farther you shoot the greater the error.

Mark

 

[MontanaRifleman]

I believe the best way to make sure every thing is right is to shoot the rifle. I eyeball the reticle and get as close as possible and then zero the rifle at 100 yards. Then use a target with a vertical line that is at least 24 inches high with an aiming point at the bottom of the vertical line. Use a plumb bob and make sure the line on the target is perfectly plumb. Make sure the rifle is level and fire the first group at the aiming point which is on the line at the bottom of the target. Next dial in 20 moa or so of elevation. Reaffirm that the rifle is still level and fire at the same aiming point as before. If the group stays on the vertical line then you are good to go. If the group is to the left or the right of the line then you need to rotate the scope and try again until the scope tracks straight up and down the line. Sometimes the reticle can be canted inside the scope and you need to make sure the vertical travel alignment is correct more so than the reticle being level. They should be exactly the same but sometimes they can be off a little.

David

I used to eyeball the reticle and that worked good for conventional shooting, but after watching the guy mount my NF with levels, I thought that was definitely better. And I agree, that shooting groups at different MOA settings is a god way to check it out. JMO