Confused with zero @ 100

[MistWolf]

Let's see what Molon's ballistic chart shows. The red line is a 36 yard zero which puts the bullet about an inch high at 50 yards. The green line is a 100 yard zero

That shows an impact between 3 inches high at 100

25 yard zero. Bullet path is about 2 inches high at 50 and about 6 inches high at 100

What Sierra shows for their 55 FMJBT http://www.exteriorballistics.com/ebexplained/4th-rifle_tables/pdf/22455fmjbt.pdf

 

[Tangodown911]

I think we have concluded that no bullet ever rises once it leaves the barrel...?






Lol

 

[Sterling Shooter]

+1

No offense to Sterling Shooter; but please explain your last comment of how an arc of ballistic trajectory must ALWAYS intersect the line of sight twice? Just as I related a ballistic curve to an inverted parabola equation on a coordinate grid; you CAN have only one intersection point on the line of sight. As MistWolf also explained, geometry plays a huge part here. Treat the X axis on a coordinate grid and the line of sight as the same. Also the inverted parabola equation and the ballistic curve the same. Both the optic plane and the X axis are horizontal. The ballistic curve follows a quadratic equation. The equation, or ballistic curve can intersect the X axis, or the line of sight once, twice, or not at all. It is basic geometry.

Here's what's basic: the shortest distance from a to b is a straight line, therefore when a straight line intersects an arc extending the distance from a to b, since the arc is always a longer distance, there will always be two intersection points if the straight line actually intersects the arc and the arc has any length. This may be miniscule, and as Graham stated, over thinking it. For practical applications such as in zeroing a rifle for a BSZ the visual of the line of sight intersecting the bullet path twice helps the shooter understand essentially how he can for example sight-in at 25 meters for a zero at 300 meters. Only if the bullet path between points was a straight line and not an arc could the line of sight actually only intersect it once. remember, the arc has length, it is not straight and it is not a point.

 

[alman1531]

This is turning into a spitting hairs argument. MOST bullet paths will indeed intersect the line of sight twice. However some paths will rise on their arc from the bore axis only to touch the line of sight without going above it. The picture I posted earlier from Demigod's article is one example. The 100yd zero only touches the line of sight once at the 100yd zero distance. The 200yd zero is on the downward arc intersecting the line of sight twice. I think most of us have answered the OPs original question and I am not interested in getting super analitical. Safe shooting everyone, I'm out.

 

[Sterling Shooter]

This is turning into a spitting hairs argument. MOST bullet paths will indeed intersect the line of sight twice. However some paths will rise on their arc from the bore axis only to touch the line of sight without going above it. The picture I posted earlier from Demigod's article is one example. The 100yd zero only touches the line of sight once at the 100yd zero distance. The 200yd zero is on the downward arc intersecting the line of sight twice. I think most of us have answered the OPs original question and I am not interested in getting super analitical. Safe shooting everyone, I'm out.

View attachment 33268

Well, I agree it is splitting hairs but it was you that asked me to explain.

 

[shovelstrokeed]

I think we have concluded that no bullet ever rises once it leaves the barrel...?






Lol

Not really, if the barrel is pointed up it will rise, BUT, from the time it leaves the muzzle it will undergo an acceleration of 9.8 m/sec^2 in the negative direction depending on latitude and height above the earth's center. Or, to make it simpler to understand, 1 g. It will also be slowing at some rate depending on wind and BC. The real curve gets complex to generate as the effect of BC varies with velocity. For general discussion, the real factors become time of flight, bore angle of departure and the vertical displacement of line of sight and bore axis. Plotting the curve becomes an exercise in integral calculus. Not fun by any means and well beyond the scope of the OP's question.