I'm a solid believer in natural point of aim. I have a FN Mauser in 30-06 and when I put the scope on it I placed the stock in my shoulder and took my most comfortable natural shooting position. Guess what - the gun was tilted slightly to the left. I did this several times. Since this is a hunting rifle and most all shots will be in some off hand position I wanted to be able to get a fast accurate shot. I adjusted the scope so it is straight with me aiming the gun where I was most comfortable in most hunting positions (not target shooting positions) and it is canted when the gun is placed in a bench position. I shot five deer with it this season and all were fast off hand shots. Four were from standing and one from the right well out of the natural shooting position arc. Ranges are less than 200 yds. I teach precision air rifle to ROTC cadets and know that the shooter must adapt body position to the rifle and target instead of what I did which is adapt equipment to the body. My other guns set up for target shooting are locked in with scopes and guns vertical.
Rifle canting question
- Thread starter greg788
- Start date
- Status
dagger dog
Member
Could it be that the "gunsmith" didn't want to go through the process of getting the scope set up dead vertical?
Pardon me if as I did not read throught all the previous post but on the subject of the canted SIGHTS used by the highpower shooters. Wouldn't that be a different set of rules because you have a FRONT and REAR sight to line up with the target and not just a crosshair in the focal plane?
Pardon me if as I did not read throught all the previous post but on the subject of the canted SIGHTS used by the highpower shooters. Wouldn't that be a different set of rules because you have a FRONT and REAR sight to line up with the target and not just a crosshair in the focal plane?
cracked butt
Member
If most of your shooting is going to be offhand and within a few hundred yards, having the crosshairs set up for your cant shouldn't hurt.
There are a few other considerations though: is it cold out where you hunt? Wearing extra layers will affect how the rifle fits you- what fits well in a gunshop might be ackward when you have thermal underwear, a wool sweater, a windbreaker and a thick wool coat over all of it. A canted rifle from a benchrest (supported)type of shooting isn't going to make that much difference- adjust the rifle and hold until the crosshairs have the same plumb and level as when shooting offhand.
The reason why you want to cant a rifle shooting offhand is to keep your head as straight as possible- tilting you head into the rifle causes the gizmos in your inner ears to tell your brain that you are off balance an to correct for it which makes shooting offhand far more wobbly.
There are a few other considerations though: is it cold out where you hunt? Wearing extra layers will affect how the rifle fits you- what fits well in a gunshop might be ackward when you have thermal underwear, a wool sweater, a windbreaker and a thick wool coat over all of it. A canted rifle from a benchrest (supported)type of shooting isn't going to make that much difference- adjust the rifle and hold until the crosshairs have the same plumb and level as when shooting offhand.
The reason why you want to cant a rifle shooting offhand is to keep your head as straight as possible- tilting you head into the rifle causes the gizmos in your inner ears to tell your brain that you are off balance an to correct for it which makes shooting offhand far more wobbly.
I almost hate to ask this. It is all about the learing & knowledge though.
If a rifle/scope/sights package has 0 cant then it should have 2 point blank ranges. That is the bullets trajectory passes through the line of sight twice.
If the rifle/scope/sights package has cant wouldn't it have only 1 point blank range?
Also scope/sight height over bore would be a variable. In this case would more height add to the cant problem.
All of this is in the perfect world scenario "no wind" and the like. In the real world we have more variables which we are trying to eliminate. Seem like cant is just 1 more variable. A lot depends on the context of how the rifle is used. Going from 100 - 600 yards requires to have your corrections worked out in advance any way. Estimating the range, Reading the wind & knowing how to adjust for it is probably a bigger issue for most of us.
If a rifle/scope/sights package has 0 cant then it should have 2 point blank ranges. That is the bullets trajectory passes through the line of sight twice.
If the rifle/scope/sights package has cant wouldn't it have only 1 point blank range?
Also scope/sight height over bore would be a variable. In this case would more height add to the cant problem.
All of this is in the perfect world scenario "no wind" and the like. In the real world we have more variables which we are trying to eliminate. Seem like cant is just 1 more variable. A lot depends on the context of how the rifle is used. Going from 100 - 600 yards requires to have your corrections worked out in advance any way. Estimating the range, Reading the wind & knowing how to adjust for it is probably a bigger issue for most of us.
woof
Member
hmmm... seems to me the bullet would still cross the line of sight twice. The cant only comes into play when an attempt is made to change the line of sight after it was zero'd.
Imagine the scope has +1 +2 +3 and -1 -2 -3 for both vertical and horizontal. Imagine that it has a 10 degree (huge) cant and that it is zero at 100 yds. That means POS=POI at 100 yds and another distance depending on the round. In other words zero is at the center of a circle and rotating the circle doesn't change that. But off center with cant will not be what is predicted by the reticle markings or turret adjustments because they assume no cant.
In a world where gravity pulls straight down no cant just lets the scope do its full job. For hunting realities as discussed just find what works for you. This is why more hunters need to get off the bench and practice more offhand shooting out in the woods. Shooting a .22 in the woods is probably better practice than shooting your deer rifle from a bench.
Imagine the scope has +1 +2 +3 and -1 -2 -3 for both vertical and horizontal. Imagine that it has a 10 degree (huge) cant and that it is zero at 100 yds. That means POS=POI at 100 yds and another distance depending on the round. In other words zero is at the center of a circle and rotating the circle doesn't change that. But off center with cant will not be what is predicted by the reticle markings or turret adjustments because they assume no cant.
In a world where gravity pulls straight down no cant just lets the scope do its full job. For hunting realities as discussed just find what works for you. This is why more hunters need to get off the bench and practice more offhand shooting out in the woods. Shooting a .22 in the woods is probably better practice than shooting your deer rifle from a bench.
consider the lobbing trajectory of most rifle rounds. if you cant the scope, when the 'hairs are straight, the barrel is canted the opposite direction.
this will cause the bullet to lob the direction of the barrel cant and shorten the rifles range, as the round is losing some upward trajectory and traveling (let's assume) Left. you would also have to use some of your scopes windage to compensate right for the bullets path.
imagine this table laid flat, and the flat bottom line is your sight alignment. Now imagine bending the drop off curve going down through the table and you have an idea of what canting the scope/barrel is really doing.
equal and opposite reactions.
this will cause the bullet to lob the direction of the barrel cant and shorten the rifles range, as the round is losing some upward trajectory and traveling (let's assume) Left. you would also have to use some of your scopes windage to compensate right for the bullets path.
imagine this table laid flat, and the flat bottom line is your sight alignment. Now imagine bending the drop off curve going down through the table and you have an idea of what canting the scope/barrel is really doing.
equal and opposite reactions.
woof
Member
How does the bullet leaving the barrel know whether the scope is canted or not? If scope alignment mattered to bullet trajectory a bullet coming from a rifle with no sights at all wouldn't have a clue where to go.
wanderinwalker
Member
I believe the fear over canting is (mildly) over-stated. The degree required for most people to get comfortable isn't very much.
I shoot Highpower with an AR-15 Service Rifle. The only way I can get my eyes, my sights and my glasses all in line reliably is with some right hand cant. It's not much; the difference between my offhand (ever so slight left cant) and sitting is about 1 minute, maybe even only 3/4, at 100 yards. At 200 yards, yep, runs about the same difference, about 1-MOA, or 2" at that range.
My offhand has always been best with the rifle tilted to my head.
I shoot Highpower with an AR-15 Service Rifle. The only way I can get my eyes, my sights and my glasses all in line reliably is with some right hand cant. It's not much; the difference between my offhand (ever so slight left cant) and sitting is about 1 minute, maybe even only 3/4, at 100 yards. At 200 yards, yep, runs about the same difference, about 1-MOA, or 2" at that range.
My offhand has always been best with the rifle tilted to my head.
d2wing
Member
- Joined
- Nov 10, 2008
- Messages
- 6,432
wntfw, you are correct. The trajectory of the bullet and the line of sight are only in the same plane if the center of the bore is directly under the line of sight. They are not paralell to each other in any case. For example, If the rifle is sighted correctly at 100 yards, the plane forms a triangle where the arc of the trajectory crosses the line of sight, the trajectory arc passes throught the line of sight again on it's way down since they are on the same plane. Say you cant the scope to the right. If the Barrel is the left of the line of sight, the bullet be moving right when the line of sight and arc of trajectory intersect at 100 yards. The bullet will continue moving right and the arc will not intersect the line of sight again. If the line of sight and bore are canted, the bore will be right or left of the line of sight. The only way around this is to sight in the point of impact the same amount of scope offset. The planes will not intersect at all but at least will be parallel.
The arc of trajectory is always in a vertical plane.
The arc of trajectory is always in a vertical plane.
30Cal
Member
It just doesn't really matter much when you dig into it. Lets say he zeroes at 200yds with the scope offset to the left at 1".
100yds: he'll be 1/2" left of center and 2.5" high
200yds: zero
300yds: he'll be 1/2" right of center and say 9" low
400yds: he's going to need a lot of elevation and he will need to make real corrections (more than a full minute) for wind if it's not calm. And he'll need 1/4 minute L to compensate for the scope offset.
...
800yds. A fist full of elevation clicks a couple for wind, and less than a half minute wind for the scope offset.
Besides the fact that OP said it's for offhand. The scope being offset is not going to contribute to a miss at any range.
30Cal
Member
You cannot cant the barrel. The barrel is pointed at the target and slightly elevated to account for drop. Sometimes, it needs to be pointed ever so slightly into the wind.
We're not messing with the barrel or the target or the flight of the bullet here. We're simply moving the observer. If you mounted the scope two blocks down the street, the barrel would still be pointed at the target. Gravity, for all intensive purposes is ALWAYS exactly vertical.
woof
Member
The way this has bounced around with no conclusion, I think we are all qualified for seats in congress 
d2wing
Member
- Joined
- Nov 10, 2008
- Messages
- 6,432
I don't want to write a book so it depends. You will be within the amount of offset at double the distance you are sighted in for. So if you are an inch offset and zero for 100 yards you be within that inch at 200 yards disregarding other factors. If you take a few shots at 25 yards with say a 30-30 with an offset scope and call it good enough, you be 7 inches left at 200 yards. A flatter shooting rifle with a line of sight closer to the bore is better because the angle is less. A big so bullet fired in a high arch and with a high scope or elevated sights will be further off. .30 cals example is correct. If you sight out at 200 yards you should be good for hunting. I hope this helps cuz I'm done.
harro
Member
G'day
Can someone tell how to check if my scope is mounted true the bore of the rifle.
Thankyou for your time
harro
Can someone tell how to check if my scope is mounted true the bore of the rifle.
Thankyou for your time
harro
Harro,
Brandon, posted these link in post #17, 1 describes a way too check by shooting.
http://www.longrangehunting.com/articles/reticle-perpendicularity.php
http://www.longrangehunting.com/articles/canting-rifle-long-range-accuracy-1.php
There is a feeler gauge method. It requires the scope & base to both have flats. A lot of combinations don't have them. That doesn't mean the crosshairs are square or plumb to the flats or each other. I cant find a link to it.
Leuplold & other may make something but tools add up & I hate buying them to find out they are marginal.
Most rifles have no reference point to say it is level. At least you now have a method to verify with if you read the articles.
Brandon, posted these link in post #17, 1 describes a way too check by shooting.
http://www.longrangehunting.com/articles/reticle-perpendicularity.php
http://www.longrangehunting.com/articles/canting-rifle-long-range-accuracy-1.php
There is a feeler gauge method. It requires the scope & base to both have flats. A lot of combinations don't have them. That doesn't mean the crosshairs are square or plumb to the flats or each other. I cant find a link to it.
Leuplold & other may make something but tools add up & I hate buying them to find out they are marginal.
Most rifles have no reference point to say it is level. At least you now have a method to verify with if you read the articles.
i think some folks are confusing the 'cant' used in match rifles where the sights are perfectly vertical/horizontal but the gun is angled underneath them, vs a misaligned sight where the gun is vertical and the sights are spun off a wee bit, usually unintentionally.
the problem with the latter is that when you make an elevation adjustment you are unintentionally also making a slight wind adjustment as well since the elevation isn't moving straight up, but also slightly to one side.
as was mentioned previously, the bore is round so you can't really mount it crooked as long as it's tangent, and most people intentionally do not make the barrel and scope parallel because bullets are not lasers and do not travel in a straight line. most rounds are fired with the bore angled slightly up and the scope straight with respect to the target. in fact, they often exaggerate this by adding a 20 MOA base under the scope
as for mounting it correctly, that depends on what action you're using. since I mostly use flat-top AR15 style, I mount the action in a vice and use a bubble level on the rail, then i put a bubble level on the rings and a bubble level on the scope (the elevation turrets are typically flat after you remove the covers)
the problem with the latter is that when you make an elevation adjustment you are unintentionally also making a slight wind adjustment as well since the elevation isn't moving straight up, but also slightly to one side.
as was mentioned previously, the bore is round so you can't really mount it crooked as long as it's tangent, and most people intentionally do not make the barrel and scope parallel because bullets are not lasers and do not travel in a straight line. most rounds are fired with the bore angled slightly up and the scope straight with respect to the target. in fact, they often exaggerate this by adding a 20 MOA base under the scope
as for mounting it correctly, that depends on what action you're using. since I mostly use flat-top AR15 style, I mount the action in a vice and use a bubble level on the rail, then i put a bubble level on the rings and a bubble level on the scope (the elevation turrets are typically flat after you remove the covers)
woof
Member
tally, you are right but I'm convinced that long ago this thread became a case of "confusion is fun." The OP was about hunting and shooting offhand. In that situation no-one makes adjustments on their scope, if anything they just hold a little high or low in which case the canted scope matters zero.
Too bad this thread was titled canted rifle but then the OP was about a canted scope, there's the source of much of the confusion.
Too bad this thread was titled canted rifle but then the OP was about a canted scope, there's the source of much of the confusion.
Honestly I wouldn't cant my scope. Cant is something to be avoided in a gun, so why would I reinforce my cant by canting the scope? Poor judgement in my opinion. Your scope if the hairs are perfectly plumb and perpendicular can help you adjust your cant to a better vertical alignment because you have a reference while shooting to let you know your angle is cockeyed or canted and can therefore adjust to make it better.
Cant is bad, it makes your bullets go left or right instead of vertical ballistics following your line of fire. Cant to the left and your bullet goes left of your aim EVERY time.
Cant is bad, it makes your bullets go left or right instead of vertical ballistics following your line of fire. Cant to the left and your bullet goes left of your aim EVERY time.
woof, yep
just for posterity's sake, I punched in some numbers in a ballistic calculator using 168g SMK in at 2800 fps in a 10mph full value wind, and varied the cant to see how it would affect drop/wind.
The four columns are
Drop Drop Windage Windage
(in) (moa) (in) (moa)
no cant
-384.1 -36.7 110.8 10.6
5*
-384.8 -36.7 114.0 10.9
10*
-385.8 -36.8 117.0 11.2
15*
-387.1 -37.0 119.8 11.4
so basically, a 15 degree cant will move your POI down 3" and over 9" at 1000 yrds.
just for posterity's sake, I punched in some numbers in a ballistic calculator using 168g SMK in at 2800 fps in a 10mph full value wind, and varied the cant to see how it would affect drop/wind.
The four columns are
Drop Drop Windage Windage
(in) (moa) (in) (moa)
no cant
-384.1 -36.7 110.8 10.6
5*
-384.8 -36.7 114.0 10.9
10*
-385.8 -36.8 117.0 11.2
15*
-387.1 -37.0 119.8 11.4
so basically, a 15 degree cant will move your POI down 3" and over 9" at 1000 yrds.
Sniper X
Member
Canting a scope to match your natural cant is not a good idea for the ultimate in accuracy. in fact, there is a level made to set the scope at zero cant and what you should do is train yourself out of canting the rifle. BUT this is only if you want to shoot at extreem long ranges, if not and the ranges you shoot at are under say 500M then don't worry about it.
Sniper X
Member
Anyone here have a printable version of bullet drop at range for the 168gr Federal GMM in .308 by any chance? say zero at 200?
Here's the question that nobody asked (or, if they did, I missed it):
What's the pupose of this rifle?
Consider that the names invoked in this thread (Tubb, et al) are certainly master shooters, and shooting at long range, but also consider that they're doing it in a fairly static, stylized way. As in, the shooter is able to assume the same position, each time, to a degree that a "practical" shooter (hunter, designated marksman, casual shooter) cannot hope to achieve in actual use. To me, this says that they have once again tweaked their rifle to work for them while shooting a very particular course of fire.
This same tweak will probably not work as well for someone using the gun in an all-around manner (at different ranges, from different positions), unless you go to the effort of learning what your natural cant is in every position, setting up the rifle for the "best" cant, and adapting your style to meet it in every position. To me, novice that I am, it would seem much easier to set the rifle up "right" and adapt my style to keeping cant to a minimum in every position, as opposed to deliberately canting the rifle the same way each time and hoping that I am able to achieve a consistent angle through every conceiveable permutation of the field positions (in a hole, aiming across a fallen tree trunk at a 20* down angle, for example, as opposed to on a flat range, on my shooting mat, in my shooting jacket, wearing my shooting gloves, where everything is reasonably constant except the wind).
I'm not putting down high-power shooters, at all. I can't do what they do. But not every tweak that a high-power shooter makes is as beneficial in "practical" shooting as it is to them on the 600 yd line. So, unless I was setting up this rifle for a particular competition or use where I would KNOW that I have a limited number of positions and I can control my body position precisely (like benchrest or high power), I would set it up with the crosshairs perpendicular and call it a day.
Mike
What's the pupose of this rifle?
Consider that the names invoked in this thread (Tubb, et al) are certainly master shooters, and shooting at long range, but also consider that they're doing it in a fairly static, stylized way. As in, the shooter is able to assume the same position, each time, to a degree that a "practical" shooter (hunter, designated marksman, casual shooter) cannot hope to achieve in actual use. To me, this says that they have once again tweaked their rifle to work for them while shooting a very particular course of fire.
This same tweak will probably not work as well for someone using the gun in an all-around manner (at different ranges, from different positions), unless you go to the effort of learning what your natural cant is in every position, setting up the rifle for the "best" cant, and adapting your style to meet it in every position. To me, novice that I am, it would seem much easier to set the rifle up "right" and adapt my style to keeping cant to a minimum in every position, as opposed to deliberately canting the rifle the same way each time and hoping that I am able to achieve a consistent angle through every conceiveable permutation of the field positions (in a hole, aiming across a fallen tree trunk at a 20* down angle, for example, as opposed to on a flat range, on my shooting mat, in my shooting jacket, wearing my shooting gloves, where everything is reasonably constant except the wind).
I'm not putting down high-power shooters, at all. I can't do what they do. But not every tweak that a high-power shooter makes is as beneficial in "practical" shooting as it is to them on the 600 yd line. So, unless I was setting up this rifle for a particular competition or use where I would KNOW that I have a limited number of positions and I can control my body position precisely (like benchrest or high power), I would set it up with the crosshairs perpendicular and call it a day.
Mike
d2wing
Member
- Joined
- Nov 10, 2008
- Messages
- 6,432
Coronach, you are correct. The idea is that the scope, bore and stock are on the same verticle plane, not only to keep windage on the same plane as trajectory, but muzzle flip due to recoil as well. I usually put my rifle in a gun vise as vertical as I can tell, then bore sight on the corner of a building and mount the scope on the same line. The link wntfw provided is a good way to
to check it. Accuracy is a matter of eliminating or minimizing as many variables as possible. If you are not picky you're not. I am I guess.
to check it. Accuracy is a matter of eliminating or minimizing as many variables as possible. If you are not picky you're not. I am I guess.
MT GUNNY
Member
Wouldn't be much problem with a scope that has a single Reticle . But If you use a Burris Ballistic Plex For Example, you would want it Absolutely Level. Or your Point of Impact would be Left or Right when using 2, 3, 4, cross. The longer the Range the more L or R the round would Hit.
MT GUNNY
Member
You Know A red dot scope has no Horizontal Line or a Vertical Line.
Theoretically you could Install a Single Reticle Scope or Red dot Scope at a 45 Deg Angle, Upside Down. it would always hit where you Sight it in at .
Theoretically you could Install a Single Reticle Scope or Red dot Scope at a 45 Deg Angle, Upside Down. it would always hit where you Sight it in at .
- Status
