Gunsmithing Vertical Crosshair to Barrel Bore

[Killer Spade 13]

Re: Vertical Crosshair to Barrel Bore

OK, let's try this.
You are out in space where there is no gravity.

Levels don't work because there is no gravitational relationship to any heavenly body (ie the earth). Plumb bobs and hanging strings don't work because there's nothing from which to hang them, and they wouldn't work anyway even if there were!

How do you go about aligning your scope to your receiver/barrel?

 

[persistant7500]

Re: Vertical Crosshair to Barrel Bore

I may be a little naive but wouldn't this be considered a characteristic of your particular rifle that would be easily compensated for by use of DOPE. If you shoot your rifle on a frequent basis, and have kept dope, then you know already if a windage adjustment is needed at extended range, and how much is needed.

 

[Killer Spade 13]

Re: Vertical Crosshair to Barrel Bore

Naive . . .

Hypothetically speaking, this is a new rifle, new scope and new mounts.

Basically what's going on is an inane discussion on terminology.

 

[Killer Spade 13]

Re: Vertical Crosshair to Barrel Bore

The thread is about the parallel alignment of the vertical cross hair to the bore of the rifle.

If the cross hair is cocked at an angle with respect to the center line of the bore, as you elevate your horizontal cross hair for elevation,the intersect point of the vertical and horizontal cross hairs will be moving away from the desired point of impact.

Many people subscribe to the position that the horizontal cross hair has to be "LEVEL" to X axis of the receiver/barrel assembly. That is just not so. It has to be parallel.

Parallel and level are not synonymous.

 

[Innovative]

Re: Vertical Crosshair to Barrel Bore

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Killer Spade 13</div><div class="ubbcode-body">

Many people subscribe to the position that the horizontal cross hair has to be "LEVEL" to X axis of the receiver/barrel assembly. That is just not so. It has to be parallel.

Parallel and level are not synonymous. </div></div>

Think about it .......
If your rifle is level AND your horizontal cross hair is level, THEN they are both parallel.

 

[Killer Spade 13]

Re: Vertical Crosshair to Barrel Bore

OK, now suppose you have your RIFLE canted 3 degrees . . . your cross hair is not LEVEL to the barrel axis, it's parallel.

There is one, and only one occurrence, theoretically speaking, when the cross hair is level to the bore, and that would be when the bore is level.

There are, however, an infinite number of occurrences when the cross hair is parallel to the x axis of the bore, if it has been properly adjusted to a state of parallel.

There are members here who align their horizontal cross hairs to the bore with the aid of feeler gauges. They need not be concerned with the receiver/bore being level because they are merely dealing with a mechanical alignment between two planes.

 

[Lowlight]

Re: Vertical Crosshair to Barrel Bore

FYI,

When you start seeing reticles like David Tubb's DTR, there is NO vertical crosshair, it only has horizontal leveling lines as the vertical hold are canted to begin with.

You also have his rifle, like the SPECTACULAR that has offset base positions that are 0, 5, and 10 degrees offset vertical so the scope is simply leveled horizontal so the fall of gravity is straight.

There is more to just saying the answer is "A" ...

 

[Innovative]

Re: Vertical Crosshair to Barrel Bore

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">FYI,

When you start seeing reticles like David Tubb's DTR, there is NO vertical crosshair, it only has horizontal leveling lines as the vertical hold are canted to begin with.

You also have his rifle, like the SPECTACULAR that has offset base positions that are 0, 5, and 10 degrees offset vertical so the scope is simply leveled horizontal so the fall of gravity is straight. </div></div>

I agree.

 

[Killer Spade 13]

Re: Vertical Crosshair to Barrel Bore

LowLight . . .

Once again, LEVEL has nothing to do with it.

The alignment of the scope to bore is simply a a co-planar/parallel alignment of two separate but dependent planes.

If you had a straight line on a wall at "X" degrees (not LEVEL), a scope and rifle could still be aligned.

With some mechanical aid the X axis of the barrel could be brought parallel the datum line and then the horizontal cross hair of the scope could be brought parallet to the datum line (given that there is no movement in the receiver/barrel assembly)resulting in the desired co-planar alignment.

A level simply allows the receiver/barrel assembly to be aligned to an invisible datum plane (a straight horizontal line if you would) in order to create a reference by which the scope can be brought into a similar alignment.

Think of perpendicular and parallel.

 

[Boomholzer]

Re: Vertical Crosshair to Barrel Bore

Changing the reference and terminology does not make you any more correct. We understand your overly complicated points, get over yourself.

 

[Chanonry]

Re: Vertical Crosshair to Barrel Bore

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Killer Spade 13</div><div class="ubbcode-body">LowLight . . .
With some mechanical aid the X axis of the barrel could be brought parallel the datum line and then the horizontal cross hair of the scope could be brought parallet to the datum line (given that there is no movement in the receiver/barrel assembly)resulting in the desired co-planar alignment.
</div></div>

Brilliant. This =

I could use something to align the the barrel and scope.

No shit Sherlock

 

[pjparker]

Re: Vertical Crosshair to Barrel Bore

+1 for Chanonry. The rest of you are making my head hurt - I'm going to go get a beer.

Paul

 

[Killer Spade 13]

Re: Vertical Crosshair to Barrel Bore

Well, I don't think I want to teach BASIC geometry again . . .

 

[Killer Spade 13]

Re: Vertical Crosshair to Barrel Bore

No need to be snippy, Chanonry, just trying to clarify a fact.

 

[Wannashootit]

Re: Vertical Crosshair to Barrel Bore

Interesting discussion. Given that a rifle's bore is a cylinder, there's no way to get anything "level" or "plumb" to "it".

It'a all about the relationship to the way the scope itself is mounted to the rifle's receiver.

And seems to me, that getting that relationship tits is perhaps somewhat less important than reproducing that (holding the rifle's receiver/crosshairs) perfectly plumb/level when shooting.

I've just purchased bubble levels for our picatinny mounts for use when shooting. Before reading this discussion, I had failed to realize the importance of this for long range. Striving to increase the accuracy of our loads by a fraction of a minute of angle would seem to pale in terms of importance to proper shooting techniques when it comes to placing the bullet where we want it to go at 1000 yards.

 

[MAT4-82]

Re: Vertical Crosshair to Barrel Bore

Just to throw something else in. I always plumb my verticle with the rifle in my shoulder after a basic boresight. Makes no sense to me to set the scope up to an artificial relationship that will need to be countered when the rifle is shouldered. Of course this is on a rifle without buttplate cant adj. In that case you can index everything you all are speaking of and then cant the BP to the shooter.
Just my way of looking at it.

 

[Lowlight]

Re: Vertical Crosshair to Barrel Bore

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MAT 4-82</div><div class="ubbcode-body">Just to throw something else in. I always plumb my verticle with the rifle in my shoulder after a basic boresight. Makes no sense to me to set the scope up to an artificial relationship that will need to be countered when the rifle is shouldered. Of course this is on a rifle without buttplate cant adj. In that case you can index everything you all are speaking of and then cant the BP to the shooter.
Just my way of looking at it.</div></div>

This is correct and why people experience cant...

They level everything outside the shoulder and then move it when shouldered causing cant. Even if they use a level, most people will glance up, level, then move focus back to the scope, at which point they subconsciously cant the rifle because that is the natural position. I always watch shooters with levels and 90% will move after leveling because that is what is natural for them to do, the rifle sitting perfectly straight up and down in their shoulder is not natural.

The first line of David Tubb's Instructions read...

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"><span style="font-weight: bold">Level your DTR scope to your natural position.</span> The Horizontal stadia lines will indicate the scope has been leveled.
</div></div>

 

[WesP]

Re: Vertical Crosshair to Barrel Bore

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MAT 4-82</div><div class="ubbcode-body">Just to throw something else in. I always plumb my verticle with the rifle in my shoulder after a basic boresight. Makes no sense to me to set the scope up to an artificial relationship that will need to be countered when the rifle is shouldered. Of course this is on a rifle without buttplate cant adj. In that case you can index everything you all are speaking of and then cant the BP to the shooter.
Just my way of looking at it.</div></div>

This is correct and why people experience cant...

They level everything outside the shoulder and then move it when shouldered causing cant. Even if they use a level, most people will glance up, level, then move focus back to the scope, at which point they subconsciously cant the rifle because that is the natural position. I always watch shooters with levels and 90% will move after leveling because that is what is natural for them to do, the rifle sitting perfectly straight up and down in their shoulder is not natural.

The first line of David Tubb's Instructions read...

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"><span style="font-weight: bold">Level your DTR scope to your natural position.</span> The Horizontal stadia lines will indicate the scope has been leveled.
</div></div> </div></div>

Well in that case I sure hope the shooters position is nice and flat and level. If the shooter is going off the feel of the rifle in his shoulder pocket I would think a lot of variables could be introduced... variables that running a level would help to reduce.

 

[Lowlight]

Re: Vertical Crosshair to Barrel Bore

David Tubb absolute advocates a level and sells one of his own design. However a level should be viewed as a training tool and not a crutch.

If every time you look up at your level your bubble is off, that is a clue. This means your rifle needs to be adjusted to fit your position. In the case of a rifle without an adjustable butt plate, it can be as simple as rotating your scope so it remains level based on your position.

I can guarantee that if you find this condition happening, were you are constantly adjusting your rifle's level position or what you believe to be level is NOT, then adjusting the system will fix the issue. If not, you will subconsciously move it off level after looking away back to the target especially if the shot does not break within 3 to 5 seconds. Any time spend focusing on the target will only add to the chance you will move off level again. I see all the time, in fact I will go down a line and specifically watch this action. People use a level as a crutch instead of a training tool. Big mistake.

Shooting is about consistency, if you are "naturally" addressing the rifle, you will do so regardless of the position. If you mate the rifle to the shoulder pocket the same way, which feels natural to you, then doing it any other way will feel incorrect. So, if you have to constantly adjust the rifle in your shoulder pocket to address a bubble level on your rifle that is showing you are off level, then here you have bright shiny clue. Something needs to be adjusted, if that something is you, then you are dependent on watching the level throughout the entire firing process otherwise you will subconsciously move it. If you are watching the level you are not watching the target, if you are watching the target you aren't watching the level, if you are working to watch both at the same time you are taking away value resources towards putting the bullet where it belongs.

Use the level to train yourself and to identify a potential problem, then correct that problem, by adjusting the "system" ---> Rifle & Scope to you, instead of constantly adjusting you to the rifle & scope.

After a while you'll find the level is unnecessary. You're natural position will be all you need.

 

[ShtrRdy]

Re: Vertical Crosshair to Barrel Bore

Frank - I think I understand what you're saying - it boils down to natural point of aim of the system. And, so if you're on level ground, life is good - but what if you are in an awkward position, or laying on the side of a hill? - Todd

 

[Lowlight]

Re: Vertical Crosshair to Barrel Bore

Does laying on a hill change how you shoulder the rifle ?

Do you level the rifle to the horizon, no, if you are trying to observe level externally you're wrong. That is like trying to level to a target frame, as if they are square and level.

I shoot on hills all the time, come on, this is a weak argument, I shoot in the field more than I shoot on a flat square range, so tell me something I don't know.

Quartering a target is quartering a target, when you focus on a 1" dot at 100 you yards, you know what level looks like, yes ?

How you hold the rifle is what determines level, the ground does not determine that, and if it does, you need to adjust the bipod, adjust the swivel and cant, and you should be able to feel it, as it sits in your shoulder pocket.

 

[ShtrRdy]

Re: Vertical Crosshair to Barrel Bore

Thanks for the info. I didn't mean to imply that you have to use a level. I was just asking a question. This is all still pretty new to me. I don't have much field time so I can't relate to that too much. (except some prairie dog hunting with a .17 HMR) So I'm still soaking all this information in. - Todd

 

[WesP]

Re: Vertical Crosshair to Barrel Bore

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Does laying on a hill change how you shoulder the rifle ?

Do you level the rifle to the horizon, no, if you are trying to observe level externally you're wrong. That is like trying to level to a target frame, as if they are square and level.

I shoot on hills all the time, come on, this is a weak argument, I shoot in the field more than I shoot on a flat square range, so tell me something I don't know.

Quartering a target is quartering a target, when you focus on a 1" dot at 100 you yards, you know what level looks like, yes ?

How you hold the rifle is what determines level, the ground does not determine that, and if it does, you need to adjust the bipod, adjust the swivel and cant, and you should be able to feel it, as it sits in your shoulder pocket. </div></div>

But if you are on a hill that positions you in a way that your body is leaning left or right, when you shoulder the rifle and use natural point of aim, wont that mean you are leaning the rifle the same amount? If your body is cocked at an awkward angle and you normally "level" the rifle by feel.... a feel that you dont have in that position.... wouldnt you be better served by having a reference point in the form of a rifle mounted level?

 

[Greg Langelius *]

Re: Vertical Crosshair to Barrel Bore

After reading this, I'm kind of disappointed at how many folks are unwilling to take advantage of the literally decades of experience LL is bringing to this conversation. He's being as practical as anything I've read here yet (except for the advice to go grab a beer...).

He's maybe glossing it over somewhat (it needs glossing...), but there are probably quite a number of caveats that apply to all the "shoulda/woulda/gotta be right because the logic/Bible/whatever tells me so" techniques folks apply to this question

Short answer, you can do it any number of 'right" ways, and still end up with a less than optimal solution. Blame Murphy, the guy has always had a point...

I approach it from the opposite direction. I assume that no approach is going to give me a perfect solution, then do the deed the simplest way I can, and then I take it to the range. Like LL says, shoot in increasing vertical increments, then correct the deviation by rotating the scope in the rings until the error goes away. What works, works.

More importantly, folks who think they can precompute perfect solutions are disregarding the real world. Murphy rules the real world.

My approach. I align the rifle in a rest so the butt pad mountings crews are parallel to a plumb line. That's as vertical as I plan to get the rifle itself. I then point the rest so the scope looks through a window at a nearby house with lap siding. I rotate the scope in the rings so the horizontal stadium wire is perfectly parallel to the siding, tighten the rings, and reconfirm that the butt pad mounting screws are still vertical.

Range time. Use LL's 'shoot and correct the scope in the rings' technique. Game over; it's as close as you're ever gonna get in this, our real world.

Greg

 

[ShtrRdy]

Re: Vertical Crosshair to Barrel Bore

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JRu</div><div class="ubbcode-body">

Sure, the ideal situation is to have the reticle both level and directly above the bore (A). However, reticle cant (B) is what really kills you, not reticle offset (C). Fortunately, when you have a canted reticle, you can make it level by canting the rifle in the opposite direction. The cant will turn into offset -- situation B becomes situation C.

As for the error introduced by such an offset, be it introduced while installing the scope, or while compensating for cant? Most of the time, too little to care.

The error by an offset but level reticle will be just the magnitude of the initial offset times the multiple of the distance the scope is zeroed to.

.1" at 0yd becomes .0" at 100yd becomes .9" at 1000yd. I personally believe I can do better than that when I just remove the bolt, eyeball the reticle to bore relationship, tighten the screws and call it good.

I obsess more about having the reticle level when I'm actually shooting. </div></div>

This is the best explanation I've seen thus far for the original question I asked. I recently thought to use JBM Ballistics to model what a 3 degree cant would do to POI at 1000 yds on my .260 Rem. As it turns out, for my bore to scope height, (~2"), the 3 degrees would amount to about 0.1" offest at the scope. Running this through JMB Ballistics, it comes up with a 2.2" offset at 1000 yd - not too much.

So, I think the bottom line is - that it really doesn't matter too much. I'd still like to get my vertical crosshair going through the center of the bore as best I can when I mount the scope.

 

[Lowlight]

Re: Vertical Crosshair to Barrel Bore

What if I am shooting upside, hangin from a tree... or how about if I was laying on my side because I ate too much for lunch ?

Sounds like a bunch of people guessing... cause they haven't done it.

The thing everyone misses in all this is, as well as, in those diagrams, in showing what it might look like the odds are the crosshair is probably not off beyond the width of the bullet you are shooting. Heck everyone puts a bit of windage in their rifle when zeroing, so that would mean there is some offset from the mechanical center of the scope, and yet we still manage to hit without have to dial that zero windage out at distance... why -- it is too small and we can't see it. or it is too large and you do see it and mistake it for something else, as in fix your rifle it needs truing.

Yes if you exaggerate the effects you can make them noticeable and certainly people love to exaggerate this stuff to prove a point. But in practical application it is a non-issue in 98.997% of the cases out there. Sure people will cant enough to cause an issue, but that is because the rifle is level and their shoulder is not, they move the rifle off center after the fact but before the shot.

Here is a great example, I took this picture during the SHC in WY, this shooter was the match winner, and I watched him level and then move off level, as I said I watch for this specifically because people make such a big deal of it.
Look:

here was the terrain the closest target here was 900 yards:

The biggest talkers shoot the least amount of shots under these conditions and will always crunch numbers and cite values, but don't' have the practical experience to show for it. There is a difference between running a series of "what ifs" and going out and doing it and recording the shots on target. If a scope manufacturer will tell you 2% off on the reticle is spec, I would guess there must be a reason for it, like under practical conditions it is a non-issue. A 1 MPH wind is 10 inches... so unless you can hold the wind to within .5 MPH, I would say:

<span style="font-weight: bold">Focus on the fundamentals, level you scope to the fall of gravity and be consistent on the stock and you'll find a lot of these problems will go away. </span>

Canting isn't as bad as lack of consistency from shot to shot, the level is there to identify your consistency. If you identify a lack of consistency you have to take steps to correct it, which should be adjusting the system unless you want to start all over <span style="text-decoration: underline">to train you</span>, which means, now that you have identified what would be a <span style="font-style: italic">"bad habit"</span> you are looking at least 9000 perfect repetitions to fix it. Any break in that perfection and you have to start all over again. So if we say this isn't a bad habit but part of our natural position, moving the system to adjust for this will lead towards consistency, why because our natural inclination is what the level showed us so why fight it.

 

[ShtrRdy]

Re: Vertical Crosshair to Barrel Bore

..... and I'm one that is still having trouble with my consistency behind the stock.

I've been mostly a pistol shooter. I have a technique that allows me to shoot consistently if I was hanging upside down, or whatever. I haven't been able to figure out how to do that with a rifle yet. I'm still learning. Thanks for the info!

 

[WesP]

Re: Vertical Crosshair to Barrel Bore

FWIW I Dont see the point in using the levels that are mounted above the scope in a place that they cant be seen while behind the rifle. Which is why I use this level that is perfectly visible at any point while behind the rifle... http://www.usoptics.com/uso-gear/accessories/ext-cant-indicator/rail-mounted-fixed-acd.html All one needs to do to check that the rifle is level (and level doesnt really matter but a consistent hold does) is to divert your left eye focus for a split second. If consistency is the key to shooting Im perfectly OK with using a crutch of some sort to aid in that consistency.

 

[Alan_H]

Re: Vertical Crosshair to Barrel Bore

TAG

 

[Lowlight]

Re: Vertical Crosshair to Barrel Bore

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: brokefromguns</div><div class="ubbcode-body">FWIW I Dont see the point in using the levels that are mounted above the scope in a place that they cant be seen while behind the rifle. Which is why I use this level that is perfectly visible at any point while behind the rifle... http://www.usoptics.com/uso-gear/accessories/ext-cant-indicator/rail-mounted-fixed-acd.html All one needs to do to check that the rifle is level (and level doesnt really matter but a consistent hold does) is to divert your left eye focus for a split second. If consistency is the key to shooting Im perfectly OK with using a crutch of some sort to aid in that consistency. </div></div>

Honestly several of the rail mounted levels have been shown to be off and not exactly level as they should be.

You're best to use a scope tube mounted level, I think the Holland is a good one, the Vortex, etc... scope tube mounted levels allow you to actually level the system as opposed to the rail mounted ones.

 

[mdesign]

Re: Vertical Crosshair to Barrel Bore

hmmm...interesting. Makes me think wonder if my stock in fitting into my shoulder consistently.

Forget the whole level vertical thing for a moment, how would I know if I was fitting the butt pad into my shoulder correctly?

 

[Straight Shooter]

Re: Vertical Crosshair to Barrel Bore

I don't believe how it fit's into your shoulder has much to do with holding the rifle in a vertical scope over barrel relationship to gravity.

 

[locked&loaded]

Re: Vertical Crosshair to Barrel Bore

Great thread. Made my head hurt a bit though.

 

[MAT4-82]

Re: Vertical Crosshair to Barrel Bore

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: *Straight Shooter*</div><div class="ubbcode-body">I don't believe how it fit's into your shoulder has much to do with holding the rifle in a vertical scope over barrel relationship to gravity. </div></div>Its about consistancy, Any variable you can eliminate makes for a better shot delivery.

 

[cozmacozmy]

Re: Vertical Crosshair to Barrel Bore

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MAT 4-82</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: *Straight Shooter*</div><div class="ubbcode-body">I don't believe how it fit's into your shoulder has much to do with holding the rifle in a vertical scope over barrel relationship to gravity. </div></div>Its about consistancy, Any variable you can eliminate makes for a better shot delivery. </div></div>

It's about spending time shooting your rifle. An old friend that is the best shot that I know of. On one of his prairie dog guns I swear the reticle is off visually by my micrometer eye when shouldred. He has folders and folders of data that are as thick as a phone book about every shot he has put through that gun. He consistently hit prairie dog's at 600 yards with ease. Using a level to install your scope is only to get you in the ball park. You must shoot it and track where the shots hit vertically to know if the scope is "level" with gravity and adjust accordingly.

 

[mdesign]

Re: Vertical Crosshair to Barrel Bore

I would agree it is about consistancy. I am thinking about some of the earlier discussion in this thread regarding how guys would level up and then move off level as they settled in for the shot.

I am thinking that this happens because they default to a natual hold position and have their eye "calibrated" to what the crosshair looks like when they do so. That could be why they are leveling up and then moving off level. They still shoot well because they do it consistantly.

I think I will do some testing to find position that I naturally shoulder the rifle at and then level my scope to gravity will I hold the rifle in my natural position. It may or may not perfectly align my vertical crosshair with my bore but I would not be surprised to find that it works okay.