Leveling scope reticles

[MK2750]

Originally Posted by DaleJ

Square to target yes. Square to receiver not important!

Dale, I am sorry you don't get this but I am at a loss at how to explain it to you.

The bullet drops straight down every time. If the verticle post is not sguare to the action your hold over will not work.

But holding the cross hairs square to the target only you can not even chase the point of impact by adjusting the scope straight down.

Your line of sight and the bore of the rifle are not on the same plane they intersect each other at two different points. You are actually looking in a downward angle and/or the barrel is tilted up. If they are not square to each other it is physically impossible for them to interect more then once.

[MK2750]

Originally Posted by Dmay

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.

I give up.

Go to the range and sight in at 200 yards zero. Then lay your rifle on it's side and try to same shot. You will find out for yourself.

[tchardy1972]

I always have my scopes level with the rifle. It can be thought of like this. If I take a handgun of some sort, hold it straight the recoil will be up and back. If I hold it sideways it is now sideways and back. So, if your not holding your rifle straight the recoil is not straight up and back. That's going to make for pretty tough shooting at long range. However, David Tubb just wrote an article for one of the gun rags that's says to can't your rifle to help get in a better position. He is also talking of open sights from a sitting position so not sure if this applies here or not.

On my f-open rig the bipod is set up so the rifle sits level and is locked in place. No canting errors are possible.

[DaleJ]

The diagram you posted clearly illustrates the canted bullet departure with the canted rifle. The diagram shows what happens when a horizontilly level scope is mounted on a canted rifle.

[harv3589]

I have no clue my head hurts

[Dmay]

Originally Posted by MK2750

I give up.

Go to the range and sight in at 200 yards zero. Then lay your rifle on it's side and try to same shot. You will find out for yourself.

Lets try this: I go and zero at 200, with my scope perfectly level to my reciever. Then I lay the gun on its side, but my scope magically, because of the gravity sensitive bearings in the rings, stays perfectly level to the world like it was before. Where is impact?

[Huntnut]

Originally Posted by Dmay

Lets try this: I go and zero at 200, with my scope perfectly level to my reciever. Then I lay the gun on its side, but my scope magically, because of the gravity sensitive bearings in the rings, stays perfectly level to the world like it was before. Where is impact?

Same situation except your sighted in at 200 yds but shooting 300yds. Where is the impact? It won't be in the same spot as when everything is level to your reciever.

[6.5 shooter]

Trajectory.. on the magic sideways rifle would but the bullet to the right 1.5"(if you laid the rifle down on it left side) or whatever distance is between the rifle bore and the optic center of the scope and the bullet at 200 yards would hit about ~ 5" low or possibly more.

When a bullet leaves the muzzle of your rifle it is going UP not in a straight line, so the bullet crosses the line of sight TWICE in its TRAJECTORY to the target. Crooked cross hairs will hit the bulls eye at whatever range the rifle is sighted in for but at any other distance the bullet will either fly left or right depending on the cant.

Guys like Tubbs are shooting at KNOW distances so they can cant their rifles and still be on target. Silhouette shooters do it all the time.

[SkytopBrewster]

Is there really an argument here? Wow, there is a reason those scope install toolkits come with levels. I suppose square to the shooter would work if you shot at the exact same range every time.

[Percher]

If it isn't required to level a scope to the rifle.....try this, turn your scope in the rings so the reticle looks like this (X) while the rifle is held straight up and down. Then sight it in at 100 yards while canting the rifle so the reticle looks like this (+) on the target and shoot a group of 3. Next put up a target at 200 yards and shoot another group holding the rifle the same canted way. That is an exaggerated scope mounted to the shooter. Post a picture of the two groups.

[DaleJ]

Originally Posted by Percher

If it isn't required to level a scope to the rifle.....try this, turn your scope in the rings so the reticle looks like this (X) while the rifle is held straight up and down. Then sight it in at 100 yards while canting the rifle so the reticle looks like this (+) on the target and shoot a group of 3. Next put up a target at 200 yards and shoot another group holding the rifle the same canted way. That is an exaggerated scope mounted to the shooter. Post a picture of the two groups.

Waiting for the pictures. ........... still waiting.

[Dmay]

Originally Posted by Dmay

Lets try this: I go and zero at 200, with my scope perfectly level to my reciever. Then I lay the gun on its side, but my scope magically, because of the gravity sensitive bearings in the rings, stays perfectly level to the world like it was before. Where is impact?

I see the flaw in what I'm trying to portray. I am presuming the scope and bore to be parallel. In my silly scenario, with a sloped base, the shot would be way left (rifle laying on its left side).

[DaleJ]

Originally Posted by SkytopBrewster

Is there really an argument here? Wow, there is a reason those scope install toolkits come with levels. I suppose square to the shooter would work if you shot at the exact same range every time.

If cross-hair is square to target and scope is adjusted up which way will your bullet go? If the rifle is canted and the scope is square on target and you need to move left, which way would you dial your scope? For long range shooting scope needs to be square to target. Forget being square to the receiver if that changes being square to target. This ain't rocket science a level scope tracks as it should, a scope canted on target does not.

[Huntnut]

Originally Posted by 6.5 shooter

Trajectory.. on the magic sideways rifle would but the bullet to the right 1.5"(if you laid the rifle down on it left side) or whatever distance is between the rifle bore and the optic center of the scope and the bullet at 200 yards would hit about ~ 5" low or possibly more.

When a bullet leaves the muzzle of your rifle it is going UP not in a straight line, so the bullet crosses the line of sight TWICE in its TRAJECTORY to the target. Crooked cross hairs will hit the bulls eye at whatever range the rifle is sighted in for but at any other distance the bullet will either fly left or right depending on the cant.

Guys like Tubbs are shooting at KNOW distances so they can cant their rifles and still be on target. Silhouette shooters do it all the time.

This expalins it about as clear as possible.

[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.

[6.5x47 lapua]

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.

bingo! reality check in full progress!

[deanmc]

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.

But with the rifle canted the scope will not be plumb to the barrel. Isnt it the same as mounting a scope slightly beside the barrel?

[Pathfinder76]

I find it simpler to start with things that are level. If you shoot a rifle that is square to its scope you will soon find yourself holding said rifle square. A fairly novel concept.

What guys that don't hunt but give advice regarding the sport fail to realize is that in any given shot scenario there can come a dozen different shooting positions. Hardly ideal if you levelled your scope to your crooked offhand stance. Whereas if you have mounted your scope correctly and your laying in a sheep trail using the side of a rock as a rest you can level your rifle to make the shot. Another novel concept.

[twofifty]

dean, I know it seems wrong but think of this:

Rifle actions are re-barreled with barrel blanks. The blank is a cylinder that has a cylindrical chamber cut into it. It is then threaded and spun onto the action such that headspace can be set to specs. The 'smith stops turning & tightening (think of it as the equivalent of canting) the barrel when headspace is set. He does not turn the barrel so that a hypothetical part of it is 'up'. The barrel, before and after headspacing, has no up or down. It just is.

The up or down part comes when rifle sights are milled into the 'top'. A canted hold on an iron sighted rifle is bad because the sights will be off level. Sight adjustments will cause the bullet to impact in the way that MK2750's diagram shows.

It is different with a scope:
At initial sighting in, the scope can be rotated in the rings such that the reticle is level relative to the target while the shooter holds the rifle canted. Reticle adjustments will cause the POI to change in the normal predictable way: up-down and left-right. OTOH, reverting to a level hold with the same setup will cause the bullet to impact per MK's diagram.

I've never shot a rifle with a side-mount scope, but there is no doubt that the laws of optics, mechanics, flight dynamics and gravity will continue to apply.

[twofifty]

Originally Posted by chuck

I find it simpler to start with things that are level. If you shoot a rifle that is square to its scope you will soon find yourself holding said rifle square. A fairly novel concept.

What guys that don't hunt but give advice regarding the sport fail to realize is that in any given shot scenario there can come a dozen different shooting positions. Hardly ideal if you levelled your scope to your crooked offhand stance. Whereas if you have mounted your scope correctly and your laying in a sheep trail using the side of a rock as a rest you can level your rifle to make the shot. Another novel concept.

I agree that a 'square hold' stance and a level scope setup are ideal.
But lots of guys hold with a bit of cant. Just look around you next time you're at the range. It takes discipline and training to get rid of mild rifle cant.

p.s. live tree trunks can be useful levelling references, so long as they aren't standing in a slide path.

[Lemonz]

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.

If you spent lots of money on a scope levelling kit but don't have a permanent level on your scope or rings you wasted your money. You can't rely on visually aligning vertical in a natural setting. On a nice flat range it's easier. The longer the distance the greater the effect.

Thanks

Lemonz

[MK2750]

I can't believe so many of you can"t fiqure this out, especially a custom gun maker.

The bore and the line of sight are on different lines. If the scope was looking right down the bore you guys would be correct, unfortunately it is not.

A rifle canted slightly to the left with the cross hairs straight up and down will throw the bullet left and low. The farther you shoot the farther left the POI.

[deanmc]

Originally Posted by MK2750

I can't believe so many of you can"t fiqure this out, especially a custom gun maker.

The bore and the line of sight are on different lines. If the scope was looking right down the bore you guys would be correct, unfortunately it is not.

A rifle canted slightly to the left with the cross hairs straight up and down will throw the bullet left and low. The farther you shoot the farther left the POI.

Makes perfect sense to me.

Originally Posted by Lemonz

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.

If you spent lots of money on a scope levelling kit but don't have a permanent level on your scope or rings you wasted your money. You can't rely on visually aligning vertical in a natural setting. On a nice flat range it's easier. The longer the distance the greater the effect.

Thanks

Lemonz

Hmmmmmm you forgot to add geometry to your physics equation.

If the scope is plumb with the barrel then your bullet will infinitely follow the path covered by the vertical cross hair.

If your rifle is canted left or right you will have to adjust the windage and elevation slightly to intercept the bullet path at a set yardage. Depending on rifle cant, the bullet will be travelling on one side of the vertical cross hair until it reaches this intercept point. After passing the rifle zero or intercept point the bullet will cross over and travel progressively farther away from the verticle crosshair.

Of course this would all need to take place in a weightless vacuum because the effect is either reduced or exaggerated by such factors as gravity, bullet spin, wind, air pressure, humidity, etc.

It doesn't take very much shooting to observe this if you are looking for it. It can actually be quite noticeable even at 300 yards.

PS. There is almost always a level reference in a natural setting. Ask any good catskinner or excavator operator. It is quite rare to have nothing around you to judge level or plumb from.

[DaleJ]

Originally Posted by Lemonz

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.

If you spent lots of money on a scope levelling kit but don't have a permanent level on your scope or rings you wasted your money. You can't rely on visually aligning vertical in a natural setting. On a nice flat range it's easier. The longer the distance the greater the effect.

Thanks

Lemonz

MK since you don't believe me or a custom rifle builder or Lemonz, maybe someone famous making the same observation is believable.

A quote from Brian Litz' Applied Ballistics for Long-Range Shooting, "As long as the sights are level, the windage and elevation adjustments will track properly and it won't matter that the rifle is canted".

[catnthehat]

Effects of Rifle Canting at Long Range — David Tubb Explains

"Eleven-Time NRA National High Power Champion David Tubb knows a bit about long-range shooting. One of the key factors in long-range accuracy is making sure that the tilt/cant of your rifle does not change throughout your shot string. In the clip below, the first in McMillan’s Master Class Video series, David Tubb explains the importance of keeping your rifle level. He explains that, at 1000 yards, your Point of Impact can change dramatically by canting the rifle either right or left. David states that, when shooting at 1000 yards, if your rifle is level and your shot is centered-up on a 72″ (six-foot) square target, you can actually put your next shot OFF PAPER by canting your rifle. That means you can move Point of Impact (POI) three feet or more, just by canting your rifle!"

Bryan Litz confirms Tubb’s observation. Bryan tells us that, as a general rule of thumb (for common cartridges), a 1° cant will produce five (5) inches of lateral displacement at 1000 yards. Thus, if you cant your rifle just 8°, the POI would move 40″ from the center of the target, putting the shot off the edge of a 72″-wide target.
This is also a cut and paste from an article of Brian litz and David Tubb.

I find it very amusing that some of us fuss with the tiniest details of hand loading , and making sure a specific powder is weighed and poured into a case that is micro measured in every aspect , then seat a bullet that has been spun, weighed, coated and fussed about in minutiae, take into effect even the barometric pressure of the condition, the corealis effect and so on, then we don't worry about a canted scope on our rifles!!

The bottom line here is consistency.
If you keep your form consistent, all is good ,
if one cants their rifle the same way every time, accurate sight adjustments can be achieved with ease

HOWEVER, if the gun is not canted the very same every time one will have problems.
I've always found that if things start off level, it's easier.
How one ensures that the complete package is level is another whole ball of wax.......
Cat

[TomCanuck]

I agree with what Cat says completely. I would also add, that the bigger the horizontal displacement of the scope is from the center of the bore, then the greater the shift in POI as the range to target changes.

I think the only place it has significant impact is with long range shooting. For average hunting shots not something to worry too much about.

[Pathfinder76]

Can someone please tell me what the harm is in making the scope level to the rifle?

[tchardy1972]

Originally Posted by chuck

Can someone please tell me what the harm is in making the scope level to the rifle?

I can't figure out what else you would level it with.

[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.

[Lemonz]

This is how some folks keep their scopes level to gravity.

http://www.brownells.com/optics-moun...ices/index.htm

When you are talking about slight MOA adjustments and being able to see them by eye it's kinda funny. Next time I need a picture hanging I'll get a backhoe driver not a spirit level to do the job.

As Cat said distance amplifies the effect. The average 100-200 yard shot, as long as your sights are close to plumb, you won't notice the difference.

Lemonz