Posted on 05/02/2013 9:22:02 PM PDT by LibWhacker
Bump
What is it that prevents someone from using the same scale when trying to illustrate a point?
Because the top scale is 10 times taller than the bottom scale the improved sighting looks worse at first glance!
I have somewhere a clipping from a hunting magazine showing how to sight in rifles at 25 yards and how it will react down range.
Doesn’t really make sense to me. The cartridge is the same, so why would it not rise the same amount over the same distance? Total bullet rise over 175 meters is 12 inches in the first graph. That should stay the same no matter where your zero is. There can’t be another 10” of drop from 0-12 meters on that second graph, can there? And why is the rise so much steeper in the second graph anyway? The curve should stay the same.
Should have added: if anything, the curve in the second graph should be shallower, since the horizontal scale is longer.
From what I understand, even with a level barrel, the .223 round does have a bit of rise; something to do with the spin of the bullet.
I guess people just like to fill up the entire graphical area from top to bottom and from left to right, so you can see the curve better. But I’m with you, unless keeping both scales the same obscures the behavior of one of them, I say keep the scales the same!
Correct! It’s no wonder anyone who thinks differently can’t hit the broad side of a barn!
If you are zeroed at 1000 yards, say (just to look at an extreme case), your sights will cause you to shoot at a much greater angle, so you can hit the target out at 1000 yards. But this is also true at all distances at which you engage a target, causing you to miss high (if you don’t compensate by fiddling with your elevation and windage). So I guess that’s what the troops were doing... Just shooting without bothering to compensate for the distance.
The curve is the same.
First principle. There is no such thing as bullet "rise". From the instant the bullet leaves the muzzle, it is dropping wrt the barrel bore line.
The sight line is aimed below the bore line to intersect the buller trajectory. At 25m the sight line cuts the trajectory early (and again c300m) to take a big "slice" out of the trajectory, consequently difference between curve and straight line is large.
At 50m (and c200m), the slice is smaller, shallower, consquently narrower, and the sight line is always closer to the trajectory
“That should stay the same no matter where your zero.”
Imagine a rifle with a scope, and the center of the scope is exactly 2 inches above the center of the barrel. If both the scope and the barrel are perfectly horizontal, if I aim through the scope at a target x at 10 yards, the bullet will strike 2 inches below the x. If I aim through the scope a target x at 50 yards, the bullet will strike about 2.01 inches below the x.
Does that help explain? When a rifle is zeroed in at a certain distance, meaning that we adjust the scope until the bullet hits the center of the x on the target, that means that the line of sight through the scope and that the aim of the barrel are not parallel to each other. In fact, one can draw three lines: (1) line from the center of the scope to the x on the target [this first line is the “sight line”]; (2) line from the x on the target to the center of the barrel; and (3) line from the center of the barrel to the center of the scope. these three lines from a triangle, with two very long sides and one very short side. In fact, assume a 50 yard zero, the two long lines are 50 yards and the short line is 2 inches.
Therefore, while firing a rifle with a scope, assuming that the rifle is zeroed in at some reasonable distance, if the sight line is perfectly horizontal, the barrel will be pointed slightly up from due horizontal.
The difference in the two ballistic graphs (one with a 25 yard zero and a second with a 50 yard zero) is that with the 25 yard zero the barrel is pointed higher.
P.S. I intentionally did not use metric measurements. Sorry, still rebelling from being told during elementary school that the US would go to the metric system-—ha!
Bookmark for later.
Why does everything have to be in metric these days? I’m an American, and I like our traditional English measurements.
I know, I know. Base ten makes more sense, but dammit, I wasn’t raised on that system and can’t re-adjust overnight.
A modest ballistics program, a bit of info on your cartridge and rifle, and you can make up your own zero range according to your estimated needs.
For iron sights and 7.62mm ammo, I still believe in the good old Marine Corps 300 yard battle sight. For scope use, 100 yards and knowledge of the drop at range work just fine. A 22-250 would be quite different were I to have one.
I had to laugh at some episode of Discovery or something showing a "secret" sniper method of shooting through a hole in a close-in screen that would mask the shooter. It was obvious they were shooting through the first zero and using the screen to mask the shot. Some secret.
Of course, ballistics geeks know all about the first zero crossing happening well before the long range crossing and the ability to do a prelim sighting in at that close range first. Firing at the real zero range almost always seems to be a touch off, but that is the fun of shooting after all.
I’m with you! We don’t need metric. We’ve never needed it. In fact, I maintain that if you need a simplistic intellectual crutch, like the metric system, you should go into art and poetry and leave the sciences, engineering and the actual building of things to people with a head on their shoulders!
Wow! That’s the “Ah, I get it now” graphic.
Right you are!
I hate metric with a passion.
Traditional measurement are just second nature, requires no thinking hardly.
Give me something in metric and I have to go through mental gymnastics to picture some distance that used to be automatic.
Don't get me started on stinking metric bolts and metric tools.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.