Range settings and tang sights

[El Chivo]

I wanted to bring up something that has perplexed me.

When shooting through a scope or fixed sights, you use the same setting for 25 yards and 175 yards, more or less. The idea being that at 25 yards the bullet is on the way up, and at 175 yards it's on the way down.

Yet, with a tang sight, the 175 yard setting is much higher than the 25 yard setting. Now, maybe the 175 yard setting will punch a hole at 25, but will the 25 yard setting punch a hole at 175?

I can't quite grasp it.

[Ysabel Kid]

Hmmm... I'd love to hear the answer on that one as well. The type of sight one uses should have absolutely no effect on the path of the bullet in flight.

[3t-]

Ok,

Just a wild guess here but to my thinking the tang site method uses 2 reference points. Rear and front sight and so has a different "line" of sight than the scope. The scope uses 1 reference point and has a different "line" when sighting.

Now this probably makes no sense and I need to go have another cup or two of coffee and then come back and delete this post.

[Gun Smith]

I think the reason for the difference is the height over the receiver with a scope. The tang sight and open sights are virtually parallel with the bore, whereas the scope can be between 1" and 11/2" higher. OK, now that's a starting point, lets let the engineers here take over.

[Terry Murbach]

GUNSMITH IS CORRECT. IT HAS TO DO ENTIRELY WITH THE HEIGHT OF THE SIGHTS ABOVE THE BORE LINE. NOTHING MORE NOTHING LESS. SIMPLE MATHAMATICS WILL TAKE IT ALL FROM THERE. WERE THE SIGHTS A FOOT ABOVE THE BORE YOU MIGHT BE SIGHTED IN AT 25 YARDS AND 1200 YARDS GIVE OR TAKE THE ODD FURLONG.

[El Chivo]

THANKS TERRY, BUT YOU AND GUNSMITH ARE ANSWERING THE WRONG QUESTION. MY QUESTION IS NOT ABOUT A DIFFERENCE IN SIGHTING IN A SCOPE VS TANG SIGHT. MY QUESTION IS WHY TANG SIGHTS HAVE ONE SETTING FOR EACH TARGET WHEREAS SCOPES CAN HIT TWO TARGETS AT THE SAME SETTING.

Well I have pondered this all day and I think I have the answer. It helps to look at your ballistics program. I did and tried different ranges and looked at the trajectories. Geez typing in all caps is not that easy.

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Imagine your rifle has either a scope, receiver, or tang sight with the line of sight 1" above the bore. If you shoot with the bore exactly level, the bullet never crosses the line of sight and you never get a zero hit on target. The bullet starts dropping right away and will always be low.

So you adjust your scope or sight to incline the muzzle slightly up. This starts the bullet on a trajectory that rises and falls, and has an apogee (high point for those of you who voted for Obama). But you didn't incline the muzzle enough to rise to the 1" difference between your line of sight and the bullet path. Again you can't get a zero hit on target.

So you adjust your sight or scope a little more. Now you have a trajectory where the bullet rises exactly 1" and starts falling. The line of sight and the bullet path intersect at one point only, and you will have a perfect hit on the target (but only at that one point).

Stay with me here. So now you raise your sights again, inclining your rifle up a little more. From this point on, the line of sight and the bullet path intersect in two places, not one. First, when the bullet path crosses the line of sight on the way up, and second, where it crosses on the way down. And it's at those places that you get a perfect hit on the target.

So I'm going to call the first intersection point, Point A, and the second intersection point, Point Z.

Now, what happens when we incline the rifle more, we get big, long trajectories with big differences between point A and point Z. When we incline the rifle less, we get short, flat trajectories with less difference between point A and point Z.

When we incline the rifle to hit at 175 yards, we get a big trajectory where point A is 25 yards and point Z is 175 yards (and the apogee is 6 inches). If we incline the rifle much less, we get a flat baby trajectory where point A is 10 yards, point Z is 25 yards, and the apogee is only an inch.

So the difference between scopes and fixed sights vs. tang sights is, the former are hitting the 25 yard target when it is at point A, (with the bullet proceeding on to point Z) and tang sights are hitting the 25 yard target when it is at point Z, at the end of a smaller, flatter, baby-sized trajectory. The bullet already rose to its apogee and is on its way down at 25 yds, whereas with the scope, the bullet is still rising at 25 yds.

I have to think then, that, for short shots, the tang sight hits harder than a scope, because the gravitational pull on a bullet traveling on a more steeply inclined path must slow it down some. The tang sighted short shot is inclined less and has to be faster.

Another thing comes to mind - it may be possible to sight in poorly with your scope and ruin your hunt. If you sight in at 25 yards, but are set so low that you are actually zeroing in on point Z instead of point A, then your 175 yard shots will be in the dirt. With your scope, you have to make sure you are really zeroing in on point A, so your bullets will go on to hit point Z at 175.

I think the difference here is tang-sighters always go for point Z. Because it's so easy to adjust the sights, there's no point in fudging it, coming up with a MBPR or finding one setting to do a dual role. But I think, without having burned any ammo to back it up, that the 175 yd setting will work at 25 also. Although the 25 yd setting will NOT work at 175.

[Griff]

No, Terry & GunSmith are entirely right. You even answer the question your last post. When sighted in at practical ranges, the bullet crosses the line of sight twice regardless of type of sight, just that with barrel or tang sights sitting so much lower to the bore, the 1st crossing may be much less than 25 yards. It is all relative to the line of bore and line of sight, which for either sight system are converging, not parallel or diverging lines. However, with iron sights that first crossing is much closer to the muzzle and... depending on the range, may be measuring in inches, or feet, not yards.

Silly me, simple boolean logic tells me that for the bullet to cross the line of sight from top to bottom (ergo the need to raise the rear sight for longer distances), it first has to cross the line of sight before it can recross it.

You're over-thinking it.

[Tycer]

Do this:

Draw a gun.
Draw an arc of bullet travel from the gun.
Draw a perpendicular line at an imaginary 25 yds.
Draw two lines above your gun, one above the other. Draw them all the way across the paper, and draw them so they intersect at the place where the 25 yard line and the bullet path intersect.
You'll have four lines intersecting at that point.
No where else on the paper will you be able to draw one more perpendicular line and have all four lines intersect.

[rjohns94]

also you said gravitational forces are more for a steeper angle than a flatter angle and the bullet hits harder. that is not correct. Gravity acts without regard to angle. energy will be the same.

[Griff]

Actually, Tycer's graphic will give you both visualizations I spoke of, simply take a straight edge and lign it at a height representing ¾" above the bore; then move the straight edge upward to a line representing 1-½" above the bore.

Go to one of the on-line sites and run a ballistics chart out using both the above measurements as the variable "front sight height above bore" and designate 1 yard as "increments". Both will begin and end with negative nmbers. That represents the distance below the line of sight.

Hope that clears the confusion... if not, then I don't understand the question either.

[Tycer]

also you said gravitational forces are more for a steeper angle than a flatter angle and the bullet hits harder. that is not correct. Gravity acts without regard to angle. energy will be the same.

True. I would think that gravity would cause a bullet to lose more velocity at XXX yards as the angle increased, measuring on the upward portion of the arc. The angles and the distances we deal with are so close to each other as to render this unusable in our world. I would imagine the heavy artillery engineers would be up on it though. Think the big guns of the 18th Century.