Rifle Ballistics Visualization

[dmarbell]

I always had trouble visualizing a rifle sighted in at, say, 100 yards shooting high at the shorter yardages. It's because of the disconnect for someone like me who has not shot much rifle, especially at distance. So on the normal graphs that show the bullet drop at 100 yards, the muzzle point is always above the impact point, or below it. Here is my rendition of the correct chart for the space-visualizing-impaired like me. Shooting a 308 on level ground zeroed at 100 yards - obviously not to scale.

 

[Dave951]

Uhmmm, your chart isn't correct. In nearly every arm, the sighting apparatus is mounted above the bore. If a straight line is taken through the sights to the target, the bullet will cross that line of sight TWICE. Once going out as it rises and again as it falls at the target. All this is dependent on how the sights are set up and what sight alignment is being used, see Iron Sights, 6oclock hold v center hold. In the case of a center hold, then the described condition is correct. If a 6oclock hold is being used, then the bullet will cross the line of sight at some distance behind the target since the sights are aligned below the point of impact. With optics, the same stuff pretty much holds true with the exception that nobody uses a 6oclock hold with optics except to compensate for some field condition.

 

[JBoyette]

I always had trouble visualizing a rifle sighted in at, say, 100 yards shooting high at the shorter yardages. It's because of the disconnect for someone like me who has not shot much rifle, especially at distance. So on the normal graphs that show the bullet drop at 100 yards, the muzzle point is always above the impact point, or below it. Here is my rendition of the correct chart for the space-visualizing-impaired like me. Shooting a 308 on level ground zeroed at 100 yards - obviously not to scale.




View attachment 449097

Here are two elements you are missing.

1. Line of sight. How high above the line of bore is the sight?
2. Line of bore, what is the angle of departure?

On your drawing you need a reference line. This line goes from your eye to the target ( line of sight ) think of the line of sight as a parallel line to the base of trajectory. ( It is )

Then place the line or bore below the line of sight.

Sights are physically above the barrel.

Now, where does the line of sight and trajectory cross? This is the short range zero.

Typically, with center-fire rifle, 100 yds is the first cross.

Now if you go, let's say 400 yds the first cross is 10yds and the flight of the bullet goes UP in the atmosphere, and down to the 400yd line.

The angle of departure, sets the pitch, or the amount of drop the bullet needs to hit at X distance

 

[BigWaylon]

I think the two replies so far completely missed the point of his post/graph…

 

[VA_GENTLEMAN]

I think the two replies so far completely missed the point of his post/graph…

I agree... I think the chart looks right as to how the OP described his visualization. It's not how I normally look at ballistics... but that is a very, very good alternate way of showing someone that does not understand the typical chart.

The Sight Over bore is the negative... as the bullet is starting out negative and climbs (through angle of the barrel and then gravity back) to two Zero's... 60yds and 100 yds.

 

[JBoyette]

@VA_GENTLEMAN and @BigWaylon

Not following,

The graph is not accurate in any way, within it's construction.

Please help me see what I am missing

 

[BigWaylon]

@VA_GENTLEMAN and @BigWaylon

Not following,

The graph is not accurate in any way, within it's construction.

Please help me see what I am missing

Sure.

Line of sight is the straight line. Bullet trajectory is the arc.

Due to gravity, the only way for a bullet to hit the mark at 100, is to “lob” it there…which explains why it’s high at all distances between 0 and 100. That’s the visualization that the normal charts weren’t giving him…

Not focusing on the technical details of POI/POA, height over bore, etc…simply looking to explain why it’s high at distances less than the sight in distance.

 

[JRV]

Sure.

Line of sight is the straight line. Bullet trajectory is the arc.

Due to gravity, the only way for a bullet to hit the mark at 100, is to “lob” it there…which explains why it’s high at all distances between 0 and 100. That’s the visualization that the normal charts weren’t giving him…

Not focusing on the technical details of POI/POA, height over bore, etc…simply looking to explain why it’s high at distances less than the sight in distance.

Line of sight starts above the bullet path by the distance between the centerline of the optic/iron sight and the muzzle. The graph should show hitting below line of sight out to an intermediate zero range, hitting above line of sight out to actual zero, and then intersecting at zero before dropping. I think that's the disconnect between the graph and folks' comments.

 

[BigWaylon]

Line of sight starts above the bullet path by the distance between the centerline of the optic/iron sight and the muzzle. The graph should show hitting below line of sight out to an intermediate zero range, hitting above line of sight out to actual zero, and then intersecting at zero before dropping. I think that's the disconnect between the graph and folks' comments.

The straight line could be bore axis…not line of sight. In this case, it doesn’t matter.

He simply wanted a chart to help him visualize how a bullet that hits the target at 100 hits higher than that from 1 to 99.

 

[BigWaylon]

The blue curved line in his pic is more useful for him to wrap his head around than the (very rough) “bullet drop” curve I added in green…



It’s probably not a chart you’d use in a class…but it’s the way to get the picture in his head.

 

[JRV]

Did this real quick on the phone.

Blue straight line represents line of sight (obviously height over bore not necessarily to scale nor representative of any particular caliber). It’s just illustrative of the line of sight.

Red line represents bore axis—the path of the bullet will only be parallel to the bore until the bullet is acted upon by gravity… which occurs immediately.

Black line represents… nothing, neither sightline nor bore, because sights aren’t mounted at bore level and bores do not point to the zeroed point of impact—I just couldn’t find a way to erase it in the photos app.



Hope that’s helpful to somebody visualizing bullet flight to zero.

 

[georgel]

 

[JBoyette]

Guys,
Only @georgel drawing is accurate.

First drawing is 100yd zero, second drawing is longer range with two intersecting points, near and far

 

[JRV]

Guys,
Only @georgel drawing is accurate.

First drawing is 100yd zero, second drawing is longer range with two intersecting points, near and far

First drawing is not applicable to OP's post, which only referred to high shots at intermediate ranges short of zero distance. If OP was using a flat zero, his initial graph would have discussed low shots at shorter ranges, not high shots.

 

[JBoyette]

First drawing is not applicable to OP's post, which only referred to high shots at intermediate ranges short of zero distance. If OP was using a flat zero, his initial graph would have discussed low shots at shorter ranges, not high shots.

Ok,

You win.

I quit.

Have a great day

 

[JRV]

Ok,

You win.

I quit.

Have a great day

Not arguing with you. Just trying to avoid confusing people that might read (i) OP's post about visualizing how his 100-yard zero hits high at shorter ranges, and then see (ii) a graph showing a flat 100-yard zero (with no intersecting intermediate zero) being called the "only" correct representation of ballistic trajectory.

Have a great day as well.

 

[JBoyette]

Ok so I am not done. LOL

I seem to drum up more confused people that do not have a visual of how a bullet gets from point A to Point B.

Let me help you all draw this out.

You need paper, pencil, a circle and a edge.

Step 1.
Line of Sight (LoS) and Line of Bore (LoB) locations.




Step 2.
From your LoB draw a 1/4 circle



Step 3.
From (LoS) draw a line to touch the Apex of the Curve and label it (1)



Step 4.
From (LoS) draw a line to touch the almost end of the curve and label it (2)



(1) is when the bullet only touches the line of sight once. This is common to centerfire 100yd sight-ins.
(2) is a long range zero. Where the bullet crosses the LOS twice, once near, and once far.

Notice, the only changing element is the line of sight, (or your location in reference to the target) the trajectory arc is the same.

John

P.S. @BatteryOaksBilly again, I fall victim. LOL

 

[JBoyette]

BTW,
I am at work the business card was the only quick line I could use to draw with.

 

[Schattenreiter]

I always thought this would make a great Mythbusters episode. Zero a rifle at 100 yards. Then install targets along the path with the cross hairs on center. Fire the shot and see where each on strikes the target with the cross hairs centered on each one.

 

[JBoyette]

I always thought this would make a great Mythbusters episode. Zero a rifle at 100 yards. Then install targets along the path with the cross hairs on center. Fire the shot and see where each on strikes the target with the cross hairs centered on each one.

I have done that.

It does not work, because the material you shoot through causes the bullet to deviate off its path.

When I taught LE Sniper Classes I always did precision shots in 10 yard increments from 10yds to 300 yards. 10 yards to 90 is done with hold overs and 110 and after is dialed DOPE. Or more accurately, gathering DOPE

Then for fun I would do Loop hole shooting, where I would place two barriers down range that had shapes cut into a plastic sheet, per barrier. Then the students had to line up the loop holes of sight, and bullet path.

FYI the line of sight that they can see does not correlate with the trajectory path...

 

[georgel]

 

[Burt Gummer]

Maybe @Michael458 can help