Regarding rifle canting and bullet strike.

PrimerBuster

On Guns and Ammo TV season 18 Episode 5  Pros Vs Joes Tom. aired on 10-19-2020, Beckstrand's bullets at 600 + yards appeared to be striking right of target (which I assume was right of his aiming point). In his synopsis he stated that he was canting his rifle to the right.  Wouldn't that cause the bullet to shoot left of point of aim?

When a rifle is canted to the left won't the bullet strike to the right of point of aim?

Was Tom's statement correct?

Your thoughts!

zorba

PrimerBuster

All I see is  your quote about getting it? Is this your response to my canting question?  If not how do I see your answer? If so your answer is Non sequitur.

JerryBobCo

Tom's statement seems correct to me, as his aiming plane was to the right of center. 

As for Zorba's response, I think he figures this will be an entertaining thread to watch.  No reason to take offense.  Believe me, give him time, and he will say something that you can correctly take as offensive.

Welcome to the forum.

Linefinder

You'd have to know if he was referring to his stock position (below boreline) or sight plane (above boreline). They'd be 180 degrees apart. 

Mike

pjames777

I just CAN'T follow this.

Linefinder

pjames777 said:

I just CAN'T follow this.

It pays to know, though. I once blew out my truck windshield because I forgot the "above/below boreline vs stock position" thingy.

It's a bit embarrassing to explain to the windshield guy why you need his services.

Mike

jaywapti

Theres an excellent artical in accurateshooter.com canting effect on POI

JAY

Linefinder

Link? I'd like to read it.

Mike

jaywapti

accurateshooter.com or 6mmbr.com

FWIW I have been on there forums for years, more first class info than anywhere else.

JAY

Justsomedude

The one that cracks me up is the folks that believe a bullet raises up from the bore line into the sight or scope line of sight after leaving the barrel. 

Linefinder

jaywapti said:

accurateshooter.com or 6mmbr.com

FWIW I have been on there forums for years, more first class info than anywhere else.

JAY

Me too. But they have so many forums, subforums, and specialty sub- sub-forums that I don't visit much anymore. That's why I asked for a link. I don't feel like searching their site all night.

Mike

Spk

https://www.accurateshooter.com/optics/canting-effect-on-point-of-impact/

Gene L

There was a young guy back then who was turkey hunting with one of those 20 ga. over a 222.  With a scope.  He sighted on a turkey and shot himself in the foot.

Linefinder

Justsomedude said:

The one that cracks me up is the folks that believe a bullet raises up from the bore line into the sight or scope line of sight after leaving the barrel. 

Yep. They're falling in the direction of gravity as soon as they leave the bore. Doesn't matter what your shooting.

Mike

PrimerBuster

The article you referred to is not canting the rifle, but canting the scope in the mounts and then shooting  the rifle as if the scope is mounted correctly.   My scenario is only canting the rifle with the scope mounted correctly.  Thank You!

Spk

PrimerBuster said:

The article you referred to is not canting the rifle, but canting the scope in the mounts and then shooting  the rifle as if the scope is mounted correctly.   My scenario is only canting the rifle with the scope mounted correctly.  Thank You!

Experienced marksmen know they should keep their rifles level when shooting. But they may not understand exactly what happens if they allow their rifle to be canted (tilted left or right), even a few degrees.

Seems like they're talking about Canting the rifle to me.

https://www.accurateshooter.com/optics/canting-effect-on-point-of-impact/

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.

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.

https://www.riflescopelevel.com/cant-errors/

Zee

Horse...........water..........etc. 

DrawbarFlats

Justsomedude said:

The one that cracks me up is the folks that believe a bullet raises up from the bore line into the sight or scope line of sight after leaving the barrel. 

That's funny! I got into an argument with a "gun expert" over that very thing. He tried to show me ballistics charts to prove his theory. "Tumbling AK Bullets" and "Designed to Maim - Not Kill" are other ones that get me laughing every time. 

Bigslug

Canting a rifle to the right will have your bullets pitch right.  Think about it:

Assuming the rifle is held perfectly level, you ARE launching your bullet on an upward trajectory.  In the case of iron sights, the rear sight has to be raised increasingly higher to connect at longer ranges.  The effect of this is that you have to lift the front of the gun higher to align the front sight with it.  This is how you lob the bullet in an arc to get more range.

SO, if you keep the sights aligned with each other the way you normally would, but you cant the rifle to the right, "UP" now becomes right.

PrimerBuster

When the barrel is level the bullet leaves the barrel level and gravity pulls it downward. It starts to fall and does not follow an arc. The reason it arcs is because of the relationship it has with the scope alignment. The scope is not parallel to the barrel, but canted downward to the front of the barrel. So when the scope is on target the front of the barrel is canted upward. Ergo , the bullet starts upward in an arc. When the scope is canted to the right, but still on target the barrel moves left. Hence the shot will hit left of aiming point..

Zee

If you think you know the answer..........

Spk

PrimerBuster said:

When the barrel is level the bullet leaves the barrel level and gravity pulls it downward.

[Yes]

It starts to fall and does not follow an arc.

[Actually, it does follow an arc because of the bullets initial velocity. As long as you're not aiming straight down or the bullet has zero initial velocity then there's an arc, even if it's really, really small.]

The reason it arcs is because of the relationship it has with the scope alignment.

[See Above]

The scope is not parallel to the barrel, but canted [Internally] downward to the front of the barrel. So when the scope is on target the front of the barrel is canted upward. Ergo , the bullet starts upward in an arc.

[Correct]

When the scope is canted to the right, but still on target the barrel moves left. Hence the shot will hit left of aiming point..

[Conditionally, See Below]

Ok, you're letting mechanical offset throw you off. Mechanical Offset is the distance between the Line of Sight and the Bore Axis.

At close range, what you are describing would happen to an extent. It's not going to happen at long range.

https://www.shootingillustrated.com/articles/2019/6/5/understanding-mechanical-offset-skill-drills-solutions/

If you're zeroed at a distance then you might have two line of sight crossings. One at the target an one much closer to the barrel. What you are describing would only happen near the muzzle where the offset exists.

Mechanical Offset is present left of position 1. Not present at position 2. Tom is correct.

I hope this helps.

PrimerBuster

This comment is for Spk.

Sorry I didn't know that when I answered yes when it asked if the response answered my question that I won't have a change to get back to Spk.

First, of course, if the barrel is level the bullet will leave in a downward arc. In my comment I indicated that it would not leave in an arc, but forgot the word upward in front of arc. If the barrel is level the bullet will leave in a downward arc because  the decrease in it's velocity is not linear and gravity has a constant pull!

Now to Spk.  Kudos to you for a well presented and illustrated reply.

I learned from your excellent explanations and graphics.

As an instructor and teacher for 47 years I have found that we are never too old to learn!!

Thank You for your knowledge and that fact that you shared it!

PrimerBuster

Bigslug

PrimerBuster said:

When the barrel is level the bullet leaves the barrel level and gravity pulls it downward. It starts to fall and does not follow an arc. The reason it arcs is because of the relationship it has with the scope alignment. The scope is not parallel to the barrel, but canted downward to the front of the barrel. So when the scope is on target the front of the barrel is canted upward. Ergo , the bullet starts upward in an arc. When the scope is canted to the right, but still on target the barrel moves left. Hence the shot will hit left of aiming point..

Looks like SPK already set it straight, but some more brain fuel for you...

The orientation of sights to the bore does not change in this equation.  You are only changing the orientation of the two in relation to the ground.

Let's assume an AR-15 with a 50 / 200 yard zero, because the effects of the sights mounted fairly high over the bore are fairly well known.

Under that system with a level gun, the bullet is launched upward to intersect with the line of sight at 50 yards, it will peak at about 1.5-2" high before gravity pulls it back down to intersect the line of sight again at 200 yards.

Regardless of the canting of the rifle, the sighting system is oriented to launch the bullet toward the line of sight, and that will be in the direction of the cant.

Because of that cant and gravity pulling at a non-90-degree angle to the line of sight, the bullet is probably not actually going to exactly cross the line of sight.  

I believe it was in one of David Tubb's books where he discusses canting the rifle to optimize the shooting position and control over the rifle.  This is fine in a Highpower competition setting where the targets do not change and the distances are fixed, but it is still a bit of a brain-bender because your windage adjustments now have an elevation component and your elevation adjustments now have a windage component.  Being a bear of very little brain, I always kept my Match Rifle level, and had a bubble in my front sight to help me do that.

PrimerBuster

We are both correct.  It depends on your reference points. When the barrel is level it is tangent to the earth's surface and because of the curvature of the earth and in relation to the earth it leaves the barrel in an upward arc until it loses enough velocity to start falling then it is in a downward arc. Also, when the barrel is level and the bullet is fired, the bullet in relation to the barrel cannot rise and begins to fall ergo, in relation to the barrel, it is at the top of a downward arc.

Linefinder

Funny.....I've shot more than a handfull of 700+ yard pdogs, and never once took the curvature of the Earth into account.

But you can damned sure have to replace a windshield if you forget the "above boreline" thing when you cant your rifle.

Just thought I'd toss in that down-to-earth advice, since I have no clue where this thread is going.

Well.....maybe I do. We'll see.

Mike

PrimerBuster

So what's wrong with my statement? Are my facts true?

Bigslug

PrimerBuster said:

So what's wrong with my statement? Are my facts true?

You seem to be proceeding from an assumption that the line of bullet departure and line of sight are parallel.   They are never will be in any normal firearm setting configured to put a bullet onto a point of aim from a non-canted firearm.  Those two lines will intersect.  Depending on the nature of the zero, the bullet will cross the line once or twice, and in a canted situation will always send the bullet in the direction of the cant.

The parallel lines situation is a non-starter other than as a mental exercise.

And I say for benefit of the entire forum:  "Bobbert, is that you?"

Justsomedude

knitepoet said:

Bigslug said:
The parallel lines situation is a non-starter other than as a mental exercise.

And I say for benefit of the entire forum:  "Welcome back Bobbert."

FIFY

Same articulated writing style and word usage. Also very fond of quoting published works.

Spk

Just for your notes, at 700 yards, the earth curves ~ 1_3/16" (1.181102") but, of course, the pdog terrain will vary more than that. But ya never know, could be useful. 😜

Linefinder said:

Funny.....I've shot more than a handfull of 700+ yard pdogs, and never once took the curvature of the Earth into account.
...

Mike

http://earthcurvature.com/