Scope Leveling; Instruction that ran counter to everything I thought I knew

[PredatorSlayer]

It’s the year of our Lord two thousand and twenty four. Please tell me you don’t think a bullet rises when it is fired from a barrel.

Once again I assume we are talking about shooting long range, so a bullet is going to rise when it is fired.

 

[Tnc]

Once again I assume we are talking about shooting long range, so a bullet is going to rise when it is fired.

Rise above line of sight due to the angle of the barrel.

 

[PredatorSlayer]

Rise above line of sight due to the angle of the barrel.

No, because gravity doesn’t influence bullets until around 300 yards or so.

 

[Marbles]

No, because gravity doesn’t influence bullets until around 300 yards or so.

?????????
I really hope that is sarcasm. I'll assume it is.

 

[Tnc]

No, because gravity doesn’t influence bullets until around 300 yards or so.

You can’t be serious

 

[Marbles]

So, there is always the question, is an effect significant. The simple answer is people dial from a 100 yard zero to make shots shorter than 300 yards, but some math and over simplified physics calculations to illistrate.

Keeping math simple. If we have a bullet launched at 3000 fps, assuming speed is constant, it takes 0.1 seconds to reach a 100 yard target (reality is longer due to velocity loss).

Gravity is acting on the bullet while it is in the chamber even, but the equal and opposite force of the barrel is preventing any drop. The instant the bullet leaves the barrel the opposing force is lost and gravity starts accelerating the bullet downwards at about 32 ft/s^2.

So, in the 0.1 second flight time, a bullet fired perfectly level will drop 1.9 inches, 200 yards will be 7.7 inches, and 300 yards will be 17.4 inches. Remember, these are under estimations because the flight time is constantly getting longer as velocity is lost.

Even with my crappy shooting and a hunting rifle gravity has what I would consider a significant effect on a bullet at 100 yards.

 

[omicron1792]

He was trolling guys. Was a well done effort. B+

 

[EdP]

So Marbles did the math and reached the same conclusion as the article JohnJohnson posted. The bottom line is that leveling the scope and rifle is a good idea because it does make a difference. The difference is small and making sure it is VERY small is easy with simple tools. I clamp a rifle in a vice pointed at the garage door and make sure it is level using a string level sitting on a bottom ring 1/2 or rail. With the rifle held level mount the scope keeping the horizontal crosshair parallel to the horizontal line of a garage door panel (previously checked with my carpenter level). No special tools, just a reasonable effort using what every man should have available or can easily get.

 

[4th_point]

Aaaand ... there's a little more to that story.

Not sure that your post helps the OP, so you may want to expand on the story with Accuracy 1st.

My only point was that Accuracy 1st has taught shooters to cant the rifle as needed to fit their body during initial setup, and rotate the scope to accommodate. Presumably given certain conditions or assumptions.

NSW, SOCOM, FBI, ICE, Army, etc. had contracts with Accuracy 1st for many years, but that might have petered out more recently.

 

[PredatorSlayer]

You can’t be serious

Well Mr Obvious, maybe I am, maybe I’m not.

 

[fwafwow]

Well Mr Obvious, maybe I am, maybe I’m not.

 

[ETtikka]

This common core math (geometry) is holding the USA back apparently

 

[IBA_270]

This common core math (geometry) is holding the USA back apparently

I resemble that remark sir. I'll have you know that I took math in summer school each year AND earned a bachelors degree without one single hour of math.

 

[BBob]

I resemble that remark sir. I'll have you know that I took math in summer school each year AND earned a bachelors degree without one single hour of math.

Sounds like me in english. I hated it. The only way out of it was summer school. Now math was a different story, liked the heck out of it and did very well there

 

[IBA_270]

Sounds like me in english. I hated it. The only way out of it was summer school. Now math was a different story, liked the heck out of it and did very well there

If it weren't for political science and English, I never would have made it!

 

[Bugger]

So many of these dumb arguments can be avoided if people just picked up a copy of Applied Ballistics…

Direct quote from the chapter titled “Cant”

“It takes a lot of vertical sight adjustment to be zeroed on a target at long range. If the rifle is canted at all, then some of that vertical adjustment bleeds over into the horizontal plane, and subtracts from the vertical plane. As an example, if it takes 300" of scope adjustment to be zeroed at 1000 yards and your sights are canted by 1 degree, you will hit over 5" to the side of your aimpoint. Small amounts of cant won't affect vertical impact nearly as much as horizontal impact. The amount of horizontal error from canting is greater as the range increases because more vertical adjustment is required.”

 

[JohnJohnson]

So many of these dumb arguments can be avoided if people just picked up a copy of Applied Ballistics…

Direct quote from the chapter titled “Cant”

“It takes a lot of vertical sight adjustment to be zeroed on a target at long range. If the rifle is canted at all, then some of that vertical adjustment bleeds over into the horizontal plane, and subtracts from the vertical plane. As an example, if it takes 300" of scope adjustment to be zeroed at 1000 yards and your sights are canted by 1 degree, you will hit over 5" to the side of your aimpoint. Small amounts of cant won't affect vertical impact nearly as much as horizontal impact. The amount of horizontal error from canting is greater as the range increases because more vertical adjustment is required.”

I don't think this really addresses what OP was asking about at all.

 

[wapitibob]

So many of these dumb arguments can be avoided if people just picked up a copy of Applied Ballistics…

“It takes a lot of vertical sight adjustment to be zeroed on a target at long range. If the rifle is canted at all, then some of that vertical adjustment bleeds over into the horizontal plane, and subtracts from the vertical plane. As an example, if it takes 300" of scope adjustment to be zeroed at 1000 yards and your sights are canted by 1 degree, you will hit over 5" to the side of your aimpoint. Small amounts of cant won't affect vertical impact nearly as much as horizontal impact. The amount of horizontal error from canting is greater as the range increases because more vertical adjustment is required.”

That's not what this thread was about.
The scope reticle was trued vertically, and a bubble level is used to maintain the reticle position, without regard to the rifle stock position or cant. As long as the level reads level, the reticle will remain trued and the barrel bore will be in the same position as previous shots. The caveat being how accurately one can repeat the level position. Canting a rifle such that the reticle is no longer plumb will shift impacts even if the scope and barrel bore are mounted vertically planar prior to the canting.

 

[BBob]

That's not what this thread was about.
The scope reticle was trued vertically, and a bubble level is used to maintain the reticle position, without regard to the rifle stock position or cant. As long as the level reads level, the reticle will remain trued and the barrel bore will be in the same position as previous shots. The caveat being how accurately one can repeat the level position. Canting a rifle such that the reticle is no longer plumb will shift impacts even if the scope and barrel bore are mounted vertically planar prior to the canting.

It still applies. A canted rifle with a plumb to ground scope will still need an offset entered into the solver to correct for the cant. If you don't there will be horizontal error just as in purely canting the rifle. It may be different with the level scope but there will still be error if not corrected for.

 

[Macintosh]

I think it addresses part of the issue. Leveling the reticle to earth with a canted rifle would address the increase in horizontal error as increasing elevation is dialed. However it doesnt address the horizontal portion of error caused by the height over bore angle(s) introduced by offsetting the scope from the vertical plane of the barrel in the first place. My little brain is struggling to wrap around exactly how that would manifest and if it would change with distance or if the angular difference would be the same at various ranges (.1 mil at ANY range just as an example of what I mean by a constant angular difference).
Whether it is a difference large enough that you could adjust it out is a separate question. Regardless it doesnt seem helpful when having a vertical rifle just doesnt seem to be hardly any burden.