Leveling scope reticles

[Ranger CS]

Dale,

These guys are right. It is a matter of basic physics, factoring in line of sight along with the ballistic line or path. Both gravity and parallax between the line of sight and the ballistic path are a factor at various distances. The scope needs to mounted square to the receiver in order to control and minimize error.

[catnthehat]

Originally Posted by DaleJ

Cat, you're talking canted sights. If sights are square to target they will track. Going to the trouble of squaring cross-hairs to receiver by using mechanical aids, then arriving at the range with your perfectly square scope/receiver, you discover your cross-hairs are canted when rifle is ready to fire. Been there, done that. Leveling scope to target works, and its a lot less expensive than changing receivers.

You missed my point completly.
What I said was that it matters not how or why, as long as the end result is a consistant hold.
However, it is easier to adjust if everything is square and level to begi with.

BUT, if one's form is not the same shot to shot, those shots will be directed to a different spot on the target.
This was aso explained in that cut and paste in my earlier post.


Cat

[gitrdun]

Originally Posted by MK2750

[IMG][/IMG]

That diagram implies that if the bullet exits the barrel of a canted rifle, it will follow a trajectory that is not concentric to barrel bore????? Hogwash, the barrel is a tube and the bullet doesn't have a mind of it's own tou know where the top of the barrel is in relationship to the real world. Who came up with this diagram anyways???

In the real world, rifle cant comes into play for a shooter that shoulders his rifle silhouette style, no rests, totally unsupported. What is the percentage of hunters that will take such a shot out to 200 yards? Pretty small I would say. And how much error can be expected then to have created in such a scenario.

I don't remember ever standing over an animal that I've shot in this manner thinking to myself....."self, you just hit the outer edge of the boiler room while aiming for center......your rifle musta been canted and scope squared to the receiver, yup that's it, better get the tools out.

[jungleboy]

From what i am reading here I get the feeling that some people would believe that if you shoot your gun upside down ,the bullet will arch upward instead of down. You have just figured out a way to defeat gravity.

[catnthehat]

Originally Posted by jungleboy

From what i am reading here I get the feeling that some people would believe that if you shoot your gun upside down ,the bullet will arch upward instead of down. You have just figured out a way to defeat gravity.

I think there would be a limit to where a canted bullet would be offset, but I'm sure however, that as the rifle goes around the clock the point of impact changes .
What I have noticed is that we often get posts ( and I am no better than anyone in this regard!) that start off with precision shooting in mind, and posts get entered concerning huntng nconditions or hunting rifles- or vice versa.
Things drift off from there.
The two conditions are very different.
As far as pure rifle accuracy goes however, all is best if everything is perfect.
Throw th huan element in and things ALWAYS go sideways!!
Cat

[6.5 shooter]

Why must ones rifle always conform to the poor forum of the rifle shooter? Why shouldn't the poor shooter conform to the squared rifle and become a better shooter?

Just a thought!

[DaleJ]

Originally Posted by Ranger CS

Dale,

These guys are right. It is a matter of basic physics, factoring in line of sight along with the ballistic line or path. Both gravity and parallax between the line of sight and the ballistic path are a factor at various distances. The scope needs to mounted square to the receiver in order to control and minimize error.

I don't understand your post, and you don't either!

[plmnnkoqaz]

I think that a lot of debate here is hung on a single principle, with each side using their own version of the facts. If a rifle is zeroed on target with the reticle and receiver square and level, then a cant will indeed cause the bullet to move left or right because of the difference between barrel and scope height. However, if the scope is levelled to the target and zeroed with the rifle canted then the only issue one will have is the slight parallax difference from the scope being offset to bore axis. This will probably only become evident at longer ranges because the parallax difference will likely be small, in addition to the natural "inaccuracy" from the off hand position. Many people have been killed from offset mounted scopes on military sniper rifles in the 20th century.

[twofifty]

Originally Posted by jungleboy

From what i am reading here I get the feeling that some people would believe that if you shoot your gun upside down ,the bullet will arch upward instead of down. You have just figured out a way to defeat gravity.

Sights are devices that allow the rifle to be tilted incrementally upward so that the bullet's angle of departure compensates for gravity's pull.

So there is a vertical angular difference between the line of sight and the barrel. This angle determines the two distances at which a bullet crosses the LOS.
The greater this angular difference, the further out your rifle's 'zero' is. For example, think of those tall ladder sights on old-school Lee Enfield 303s = lots of angular difference for shooting to 1000yds.

Now cant that same 303 90 degrees to the left. The angular value difference between the barrel and line of sight remains the same yet they no longer compensate for gravity. The bullet would not rise above the line of sight. And so the bullet ends up hitting low way out in left field.

Jungleboy, the upside down rifle you allude to would send the bullet neither left nor right, but it will strike the ground very early in its trajectory.

[savage shooter]

My take: As long as the reticle is straight up and down (and thus level) for every shot, the cant of the gun under it means nothing. The bullet will drop down the reticle. I still wonder why somebody hasn't come up with a level inside the scope to help accomplish this. Outside levels, of course, accomplish this, but only if they are perfectly aligned to the reticle.

Have to disagree. Gravity works straight down, no matter what. When the bullet exits, its starts down, straight down. If the reticle is level, it will predict the fall of the bullet.

Sir, you are correct that gravity will always pull straight down but you don't seem to understand the issue at play here. If the reticle is not level to the bore and you hold it level to the target, that means that the bore is no longer directly under the reticle. The bore would have to be slightly to one side of the reticle. If the bore is off slight to (say) the left that means that the bullet is moving a bit to the right to hit your zero at the distance that you have zeroed your rifle in. Anything less than that zero distance and the point of impact will be slightly to the left since your bore is left of the reticle and the bullet is moving to the right to meet the point of aim at your zero distance. Any distance after your zero distance and the point of impact will be to the right of your point of aim as the bullet is still travelling slightly left to right since the bore and reticle and not above/below each other.

If cross-hair is square to target and scope is adjusted up which way will your bullet go?

If your scope is canted only slightly to the bore, then if you adjust your scope left the point of impact will move left and the elevation WILL also change. If the top of your reticle is canted left, then the point of impact will drop slightly. If the top of your reticle is canted right, then the point of impact will raise slightly. Likewise, if you adjust the reticle up, you will also have some left/right movement if the reticle is not leveled to the bore, regardless of it being leveled to the target.


Sir, I hope my explanation has helped you to understand this phenomenon somewhat better. Once it clicks you will get it. It's very easy to understand if someone sits down with you with pen and paper and draws the trajectory of the bullet for you if the bore is under the reticle vs being below and, say, off 10 degrees to either side.

This ain't rocket science a level scope tracks as it should, a scope canted on target does not.

Just because the scope is level to the target, it will not track properly unless the reticle is also level to the bore. Obviously, you are correct that it will not track properly against the grid on the target unless the reticle is ALSO level on the target.

Holding the stock canted matters not, so long at the sighting system's adjustments still take place in a plumb and level context relative to the target. The cant angle (shooter's form or technique) must be constant for the scope adjustments to take effect predictably, i.e. straight up or down, left or right.

This is only true at a given distance. If the reticle is level to the target but the bore is canted to the reticle, the point of impact WILL be off either left or right at any other distance other than the one the rifle was zeroed at.

This is a fairly simple geometry exercise...

A rifle with a side mounted scope CANNOT have the same horizontal point of impact at more than one distance, period. It's impossible if the bore and reticle are not on the same horizontal plane.

This whole tread for a simple physics problem. If the reticules vertical axis is square to the force of gravity the impact trajectory can be predicted accurately (excluding other factors such as wind gyroscopic effects etc).

The angle of the gun has no effect.

This is wrong. The left and right will be affected at various distances if the bore is not directly under the reticle.

here's an exercise to do:

Take a piece of paper. Mark a scope. Mark a barrel under it that's off by, say, 15 degrees. So that barrel will be slightly off to one side of the scope. Draw a target. Draw a line from the scope to the target. Draw a line from the barrel to the target. Do you see how they only intersect at the target? The bullet would have a different point of impact at any other distance. It seems some people don't understand that if the reticle is not level to the bore then the bore is not directly under the reticle and the bullet is leaving from a different horizontal plane than the reticle.

MK since you don't believe me or a custom rifle builder or Lemonz,

I wouldn't buy anything from that customer rifle maker. This is a very well understood and documented phenomenon. It's also covered in 4th grade geometry.

[Pathfinder76]

Can someone tell me why it is bad to have a scope that is level sitting on a rifle that is level?

[savage shooter]

Please excuse the quality of this. I simply used the school supplies on hand that belong to my young son. I believe he would be perfectly capable of understanding this simple geometry exercise.

As you can see, if the reticle is not level with the bore and you cant the rifle to be level with the target, then the bore most not be directly under the reticle. You can see from the second picture the result of this. The bullet will impact to one side or other of the point of aim at any other distance than the one that is zeroed. Aditionally, the scope will not track correctly and any other distance.


upload


pc screenshot

[savage shooter]

Originally Posted by chuck

Can someone tell me why it is bad to have a scope that is level sitting on a rifle that is level?

This is ideal. Level the reticle to the bore and then when you level the reticle to the target, the bullet will leave from a point directly below the reticle allowing for correct adjustment and correct point of horizontal impact regardless of distance.

[Percher]

Originally Posted by catnthehat

As far as pure rifle accuracy goes however, all is best if everything is perfect.
Throw the human element in and things ALWAYS go sideways!!
Cat

My thoughts exactly.

If a canted gun feels better on a shooters shoulder why not attach a movable butt plate, turn it to your preference while the rifle is held vertical. They are specifically made to compensate for human error.

[6.5x47 lapua]

Originally Posted by 6.5 shooter

Why must ones rifle always conform to the poor forum of the rifle shooter? Why shouldn't the poor shooter conform to the squared rifle and become a better shooter?

Just a thought!

go watch the tr shooters at an fclass match.some of the best shooters in Canada and the world purposely cant their rifles to fit them better.you will also notice the levels on their rifles.then they manage to shoot palma matches at different distances out to 900m with little problems other than wind calls.all this while looking through peep sights.kinda puts the whole thing in perspective. when everyone is talking about squaring the crosshairs of the scope to the rifle what are you squaring it to? the action?the stock? any of these can and will be so far out of whack as to not be a viable place to level off of.this I say from experience as many rifles are not in stock square to begin with.the only viable way to square a rifle to a scope is to put the rifle in some kind of fixture and eyeball it level then use a string and a plumbob to square your crosshairs,or do like dale does and use the waterline of a target.either way you still have to have a "return to battery"with levels and shooting form no matter what.most good shooters could roll their crosshairs to form an x and make hunting quality hits out to resasonable distances on shooting form alone.

[savage shooter]

when everyone is talking about squaring the crosshairs of the scope to the rifle what are you squaring it to? the action?the stock?

THE BORE!

go watch the tr shooters at an fclass match.some of the best shooters in Canada and the world purposely cant their rifles to fit them better.you will also notice the levels on their rifles.then they manage to shoot palma matches at different distances out to 900m with little problems other than wind calls.all this while looking through peep sights.

....and even with the canted rifle, the sight has been mounted so that it is directly above the bore when the shooter holds the rifle at a cant. Thus, the bore is NOT canted to the sight for that shooter.

[savage shooter]

"Crooked scopes cause you to cant the rifle, which causes the bullet to fly to the right or the left of the axis of the bore, which means you’re going to miss right or left when you shoot at 250 yards or more. "

David E. Petzal



Here's a quick test to see if your reticle is level to your bore. Remove your bolt. Put a light in the action so that it illuminate the bore. Stand in front of your rifle (the muzzle end) so that you are looking directly down the bore. Now, look up and see the reticle of the scope. Following with your eye the vertical line on the reticle down to the bore. The further back you get, the more obvious this becomes. Does it intersect the bore in the centre? If yes, then your reticle is level to your bore. If it is pointing to either the left or right then you have some levelling to do.

[savage shooter]

HERE is a thorough explanation that should enable just about ANYONE to understand this phenomenon:

[MK2750]

Originally Posted by savage shooter

HERE is a thorough explanation that should enable just about ANYONE to understand this phenomenon:

That write up is filled with common sense, the facts of physics and the effects of gravity.

Do you really think that that applies here...on the internet?

JK, it is an excellent article but I think some folks would rather argue than think about something until they understand.

[Lefty-Canuck]

I actually mount all my scopes upside down so I gain elevation the further out I shoot.

LC

[MK2750]

Originally Posted by gitrdun

That diagram implies that if the bullet exits the barrel of a canted rifle, it will follow a trajectory that is not concentric to barrel bore????? Hogwash, the barrel is a tube and the bullet doesn't have a mind of it's own tou know where the top of the barrel is in relationship to the real world. Who came up with this diagram anyways???:

I am truly surprised you don't understand this. The bore and line of sight are not running parallel. They are angled towards each other. The diagram is correct and the bullet will fall left and low if the rifle is canted as shown.

[catnthehat]

Originally Posted by Percher

My thoughts exactly.

If a canted gun feels better on a shooters shoulder why not attach a movable butt plate, turn it to your preference while the rifle is held vertical. They are specifically made to compensate for human error.

Which is exactly why they make stuff like fully adjustable stocks!
Cat

[gitrdun]

Well I think that I do MK2750. But seeing the diagrams that are posted, we may be arguing about two different issues. The diagrams imply to me anyhow that the line of sight thru the scope isn't parallel to the barrel bore. The scope is mounted crooked in other words. The scenario that I'm on about has the scope's line of sight in perfect alignment to the barrel bore, BUT the scope is slightly twisted CW or CCW within the rings which result in the crosshairs being slanted or "canted" when the shooter naturally shoulders the rifle.

My Rem700 is just that kind of beast. I can use the Wheeler levels to level the crosshairs to the receiver as many times as I want. When I should that rifle, the crosshairs are slanted to one side. Now, I'm not about to chop the stock or get shoulder surgery to make up for it, I simply twist the scope so that the crosshairs are level when I shoulder the rifle. No other gun fits me that way, but somehow, this one does.

[savage shooter]

Well I think that I do MK2750. But seeing the diagrams that are posted, we may be arguing about two different issues. The diagrams imply to me anyhow that the line of sight thru the scope isn't parallel to the barrel bore. The scope is mounted crooked in other words. The scenario that I'm on about has the scope's line of sight in perfect alignment to the barrel bore, BUT the scope is slightly twisted CW or CCW within the rings which result in the crosshairs being slanted or "canted" when the shooter naturally shoulders the rifle.

Right, so the scope isn't canted. It's level. The shooter needs practice in proper technique

[savage shooter]

double tap

[gitrdun]

Originally Posted by savage shooter

Right, so the scope isn't canted. It's level. The shooter needs practice in proper technique

Well, blow me away, so do I. I have several rifles that I can shoot level, including those that I've shot in silhouette matches. I have one that doesn't, now I need schooling or surgery to shoot my hunting rifle. The internet is awesome....learn something new every day.

[Percher]

Originally Posted by savage shooter

HERE is a thorough explanation that should enable just about ANYONE to understand this phenomenon:

Thanks for posting that read savage shooter. This guy went through a lot of hoops to prove his point on canting and properly mounting a scope.

[DaleJ]

Savage Shooter
Save your teaching "skills" for something you know. You would get more benifit eating your crayons.

[Metalmike123]

Originally Posted by twofifty

The barrel is an inanimate cylindrical pressure vessel. It barely 'knows' that it is pointed toward the target. The cartridge, another vessel, is co-axial to the barrel. Once chambered the cartridge sees the world as the barrel does.

The scope reticle or the iron sights, on the other hand, are capable of abstract thought.

They need to be held level to the target to do their job, which is to take account of gravity in the bullet's flight so that the bullet crosses the line of sight at the zero distance.

Holding the stock canted matters not, so long at the sighting system's adjustments still take place in a plumb and level context relative to the target. The cant angle (shooter's form or technique) must be constant for the scope adjustments to take effect predictably, i.e. straight up or down, left or right.

Gotta say I love your explanation twofifty, spot on and in a very understandable context.

[savage shooter]

Originally Posted by Metalmike123

Gotta say I love your explanation twofifty, spot on and in a very understandable context.

Too bad he's wrong. What he said is only correct for a fixed point. Anything closer or further and it doesn't work.