Advanced Marksmanship Bullet path vs Bullet drop

[Tmm01]

I was looking for the most accurate method to determine come-ups on high angle shooting, when I came upon an article titled "Inclined Fire" by
William T. McDonald. In it he mentions the "Sierra's Method" but to use this method you need Bullet path and Bullet drop. Bullet path is easy enough, it is how much the bullet will drop in inches that corresponds to your come-up at a given distance, and can be found in a ballistic calculator but I can't figure out how to get the numbers for Bullet drop. I have spent two days trying to find the info and it just leads me back to the original article or a bunch of how to's, on dialing your dope on a scope.

 

[AIAW]

Bullet Path is the trajectory that the bullet takes to the target.

Bullet Drop is the distance below line of sight beyond the zero range.

I’ll read the article here shortly to see what they are talking about also.

 

[Dthomas3523]

Change your sight height to zero in your calculator.

That will give your the drop from the bore line.

With sight height entered, will give you drop from the sights.

 

[Nik H]

That is the nice thing about the Coldbore SW. It provides both drop and path simultaneously on the same output page.

 

[Dthomas3523]

That is the nice thing about the Coldbore SW. It provides both drop and path simultaneously on the same output page.

Can you see if zero sight height lines up with bullet path?

I’m shooting from the hip that it should be the same.

 

[Nik H]

Can you see if zero sight height lines up with bullet path?

I’m shooting from the hip that it should be the same.

I can certainly do it when I get back home on Friday. On a business trip and CB is on my desktop at home. However, the manual, which I can access through my dropbox account says the following....

"....drop relative to the extended bore line of the gun, bullet path height relative to the relative to the line of sight of the shooter...."

This lines up to what you are saying...I can check when I get home and let you know though

 

[wade2big]

@Tmm01 you have it backwards. Bullet path would be where the bullet is at any point along its trajectory to the target. Change your zero in your calculator to the target distance.

For example target at 1000 yards so set your zero at 1000 yards. Now your calculator lines up to the flight path of the bullet from the muzzle out until it impacts the target. The numbers shown at each distance now are representative of the true height of the bullet above the bore and not the drop that is typically seen on calculators.

If this isn’t what you guys are talking about then hey, I tried.

 

[Tmm01]

@Tmm01 you have it backwards. Bullet path would be where the bullet is at any point along its trajectory to the target. Change your zero in your calculator to the target distance.

For example target at 1000 yards so set your zero at 1000 yards. Now your calculator lines up to the flight path of the bullet from the muzzle out until it impacts the target. The numbers shown at each distance now are representative of the true height of the bullet above the bore and not the drop that is typically seen on calculators.

If this isn’t what you guys are talking about then hey, I tried.

It might seem as I have it backwards, but I used the same terms that are used in the article, so that there would be no confusion, but I think we are saying the same thing?? Per the article, Bullet path is what he is dialing into his scope, example, at 900 yards his drop is 294.49 inches and his come-up is 31.25 moa, 1.047 x 9 = 9.423 x 31.25 = 294.49. Setting the sight height to zero as was suggested seems to be the answer I was looking for.

 

[Dthomas3523]

For clarification purposes, the bullet never rises above the angle of the bore due to gravity. Even though the bore is angled up for say a shot at 1k yds, the bullet will still always drop away from that angle.

The bullet will pass through the line of sight and back down, but doesn’t go above the bore angle.

 

[Diver160651]

I was looking for the most accurate method to determine come-ups on high angle shooting, when I came upon an article titled "Inclined Fire" by
William T. McDonald. In it he mentions the "Sierra's Method" but to use this method you need Bullet path and Bullet drop. Bullet path is easy enough, it is how much the bullet will drop in inches that corresponds to your come-up at a given distance, and can be found in a ballistic calculator but I can't figure out how to get the numbers for Bullet drop. I have spent two days trying to find the info and it just leads me back to the original article or a bunch of how to's, on dialing your dope on a scope.

Use the cosign -- it is ultra simple..

for a rifle do not get to wrapped up in the axel. all you need are a few numbers.. hell you can even round them.. like 10°,15°, 20°, 25° and 40° is like hanging out a window. Sure you can add more but remember all yo are doing is calculating gravity distance (GD) vrs Line of Sight (LOS). So if the range is really short the difference between GD and LOS is often so small even extreme angles have little effect. For longer distance you be really surprised how far up a hill or down a cannon you need to be to make up 20°+.. If thats the case don't forget wind is still LOS.

edited to add: My bow at only 300FPS does indeed need to account for cosign values even at very short ranges.. Think of it is a time to gravity exposure issue more than distance.

I remember that 10° is about 2% less GD, 15° -4% 20° -6%, then 25° -10% of the LOS.. that way I do not have to even remember the cosign, set my PLRF to report GD or use a calculator..


GD= LOS distance x cos(a)

 

[Tmm01]

Use the cosign -- it is ultra simple..

for a rifle do not get to wrapped up in the axel. all you need are a few numbers.. hell you can even round them.. like 10°,15°, 20°, 25° and 40° is like hanging out a window. Sure you can add more but remember all yo are doing is calculating gravity distance (GD) vrs Line of Sight (LOS). So if the range is really short the difference between GD and LOS is often so small even extreme angles have little effect. For longer distance you be really surprised how far up a hill or down a cannon you need to be to make up 20°+.. If thats the case don't forget wind is still LOS.

edited to add: My bow at only 300FPS does indeed need to account for cosign values even at very short ranges.. Think of it is a time to gravity exposure issue more than distance.

I remember that 10° is about 2% less GD, 15° -4% 20° -6%, then 25° -10% of the LOS.. that way I do not have to even remember the cosign, set my PLRF to report GD or use a calculator..

Diver160651, I am familiar with the cosine method, but at steep angles and greater distance it can be off, but lets face it, this problem is really nothing more than academic. An 800 yard shoot at a 60 degree angle in the wild is as rare as hens teeth, but it's fun to problem solve this stuff. I still don't know if I'm doing the problem correctly because my answers are not as accurate as the ones in the article.

 

[Tmm01]

In reality, very a long range ultra high angle shot like you said is mostly academic. To shoot 60* at 800 GD, you’ll need 4,155’ of vertical, lol, you’d have to strap yourself to El Cap! Remember the the angle of repose, the steepest angle before soil and rock falls for most hills is on average about 30-35*. Sure with some cliffs 45.. over the longer average slope. Sure, if your talking 800 LoS at 60* the numbers are halved. Either way it’s hard as hell to physically shoot a gun much past 30 accurately without some weird shooter offset.

Do you have software that calculates for Gravity Distance, or are you using a specific Gravity Distance Angle calculator?

 

[AIAW]

Do you have software that calculates for Gravity Distance, or are you using a specific Gravity Distance Angle calculator?

OP: So I read the article you referenced (http://www.exteriorballistics.com/ebexplained/article1.html). There is no way I would try to run the "Sierra Method" in the field. Too slow, too involved, by hand. Running the numbers, mathematically it does solve out more accurately though indeed at sharp angles and distance. Just depends how critical you need to be over the traditional cosine method.

Most all popular ballistic apps soltve for target angle. Some for either angle degrees or angle cosine... Applied Ballistics, Field Firing Solutions, Coldbore, TRASOL, Ballistic AE, etc.

 

[Deleted member 10043]

Not long but short...

 

[Gunfighting Inc]

The myth of Ground Distance vs Line Of Sight Distance

Since we are engaging in the fun and rewarding exercise of talking the academics of LR shooting, we should understand that angular shooting is not a ground distance vs LOS distance problem. This explanation is indeed a myth perpetuated by many reputable rifle marksmanship programs, including military and LE schools. We all know what the myth states, which is that when shooting at angles up or down, the LOS to the target distance is longer that the horizontal surface of the earth distance, and that gravity only acts on the bullet at the shorter "gravity" distance. This results in less bullet drop, so if one uses the DOPE for the actual target distance, rather than the shorter gravity distance, the bullet will impact high. This is the myth. And, we know a myth is something generally accepted as true but in reality is not.

Why is the myth not true? Because gravity acts on the bullet during its entire time of flight and TOF is the same for a given distance no matter the angle being shot. There is no such thing as gravity distance, ground distance, or earth surface distance. There is just distance and time. Which means that bullet drop is the same for a given distance no matter the angle. (I know what you're thinking, stay with me)

Bullet drop is a vertical measurement. Imagine holding your rifle in a horizontal position with a string tied to the end of the barrel with a weight on the end of the string hanging six inches below the muzzle to represent six inches of bullet drop. The angle of vertical bullet drop is 90 degrees relative to line of sight in this example. Now raise the barrel up as though shooting at a high angle target. What happens to the angle of vertical bullet drop? The angle changes and moves closer to our LOS. If you raised the barrel enough, you could get the weight and string to line up with the barrel. If we fire a bullet from that position where would it impact relative to our LOS? High.

Our problem is still an angle problem of sorts, but it's an optical angular (optangular?) illusion created by the angle of vertical bullet drop relative to LOS. Because the issue is angular, the cosign solution works to a field expedient degree and helps perpetuate the myth.

 

[Deleted member 113831]

The "improved" rifleman's rule has you multiplying the cosine to the DOPE as if it was a percentage rather than to the LOS distance.

It still isn't perfect, but it is a big improvement.