And This Means What?

[diensthunds]

I was playing around with some ballistic software and came across a few things I just can't figure out.

Here's the results of the info I gave the program:

Name: .224 Cal, Speer SP, 55 gr Scope Height: 1.50 in
Muzzle Velocity: 3147 fps Target Zero Range: 200 yds
Bullet Weight: 55 grains Altitude: 500 ft
Ballistic Coef.: 0.267 Temperature: 70 F


Range Elevation Velocity Energy Total Drop Max Y
yds inches ft/s ft/lbs inches inches
0 -1.50 3174 1230 0.00 -1.50
50 0.46 2995 1096 0.45 -0.48
100 1.45 2824 974 1.86 -0.11
150 1.34 2659 863 4.38 0.57
200 0.00 2500 763 8.12 1.61


The only thing I can't figure out by the chart and the trajectory graph that the software printed is the Total Drop and Max Y.
I would assume the total drop is the amount the bullet would drop at the given distance, however there isn't anything on the graph that is printed that indicates this. There is a curved line representing the flight of the bullet but it doesn't correspond to the total drops measurements.
As for the Max Y I'm at a complete loss.

Any Ideas?
The software is Point Blank Computer Reloading And Ballistics Software v1.8a

[dozernomore]

I believe the way you would understand"total drop",is if you were to shoot your gun so the barrel was completely flat(exactly 180 deg.),total drop is the given distance the bullet will drop with respect to the distance traveled,,if you shoot across a flat field with the barrel at 180 deg,and total drop at 200 is 8.12 in....then at 400 yards it will probably hit the ground,,,

[diensthunds]

The only problem is that the software was set to zero at 200 yds so a drop of anything doesn't make sence.

[dozernomore]

that's correct,and thats why you have your 2,nd column as your 200 yard zero(elevation in inches)
and your 5'th column is your total drop in inches.
your bullet isn't self propelled,,another way to look at it is,,if you were to drop a bullet(from your hand) at the exact same time you shot a bullet from the exact same height as your muzzle,,,both bullets will hit the ground at the same time,other then te one you shot is travelling horizontally at a starting velocity of 2995 fps

[dozernomore]

and one more thing,,,thats why line of sight and line of discharge are slightly off,,when you zero your gun for 200 yards,,,your bullet isn't travelling completely horizontal,,their is a slight arc to the bullet travel

[diensthunds]

I believe the way you would understand"total drop",is if you were to shoot your gun so the barrel was completely flat(exactly 180 deg.),total drop is the given distance the bullet will drop with respect to the distance traveled,,if you shoot across a flat field with the barrel at 180 deg,and total drop at 200 is 8.12 in....then at 400 yards it will probably hit the ground,,,

In order for this to be true the bullet would have to be 16.24 inches above the ground. When I look back at the software's print out again it shows that at 400 yards the total drop is 38.96 in. and at 100 yards it is 1.86 in so there is clearly no relation to the distance traveled being double or half the drop in inches. At least as far as the software is showing. (Unless there is some convoluted equation hidden).

[Jim Watson]

Total drop is the drop from the line of the bore axis. That is what you set the sights to compensate for. I don't know what they mean by Max Y. Are there no instructions with the program?

[diensthunds]

So at 100 yards I have to set my sights 1.86 inches above the target? Even if it's being zero'd at 100 yards? this makes no sense when the scope height is 1.5 inches above the muzzle.

[Scorch]

diensthunds-
there are three crossing lines: flight path, line of sight, and bore axis. Line of sight is exactly what it sounds like: it is the line from your eye to the target. Bore axis is a line that travels straight along the same direction the barrel is pointed. These tow cross a short distance in front of the muzzle (about 30-50 yds, depending on a lot of things). When the rifle is fired, it launches the bullet along the bore axis, but the bullet begins dropping away from that line immediately due to gravity, and creates the third line, the flight path. The flight path will cross the line of sight at fairly close range (again, 30-50 yds) and continue to fly above it until its trajectory brings it back to the line of sight and it crosses and falls below it. Thus you get three different sight references, Point Of Aim (POA), Point Of Impact (POI), and Line Of Sight (LOS). When you "sight in" a rifle, you are simply adjusting the POA and POI so they coincide with the LOS at a given range. In order to do so, you shoot the bullet along a line that points higher than your intended POI and POA and the bullet "falls" into the desired POI.

"Total Drop" is exactly what it sounds like, it is the amount of drop as the bullet falls away from the line of the bore axis. When you fire at 100 yds, the bore axis is pointed at a point that is 1.86" higher than the point of impact (POI), it is not where your sights are pointed. "Max Y" is an algebraic expression of the trajectory, don't worry about it.

[diensthunds]

]The problem is the software didn't have any instructions so it's not really clear what is being represented in the graph that it prints.
1.jpg

I understand that the 0 inches line would be the line of sight.
The arcing line is the flight bath of the bullet.
There really isn't anything representing the bore axis.

I still don't understand how the bullet could drop 1.86 inches away from the bore axis when at 100 yards the bullet is hitting the target that is approximately 1.8 inches ABOVE the originating start of the bore axis as is represented by the graph.

[zippy13]

From what I see in the graph, it appears the zero range is 100-yd, not the 200-yd you thought you were using.

Check this graph for a 250-yd zero, hopefully it make more sense to you.

[diensthunds]

I fat fingered the range when I input it. I still don't understand the softwares graph though.
Even if I use the 250 yd target distance the software says at 250 yds the max drop is 13.22 inches and yet when I look at the arc of the path it is dead on zero.

[RKG]

"Total drop" is the vertical distance between:

A) The bullet in flight at the distance reported for the zero employed, and

B) An extended bore line, with the rifle aimed at a target at the distance reported (not held horizontal).

You use this to boresight the rifle for a given zero (which, if done properly, will get you on paper for a more precise range-fired zero).

"Max Y" is that program's denotation of the highest lift of the bullet in flight above the line of sight, when sighted for the employed zero. It used to be called "mid range trajectory," but this term was a bit misleading, because Max Y doesn't occur at a distance equal to half the zero distance.

[kraigwy]

The M-193 (pretty close to what you are shooting) is a funny creature.

I wished I could find the manuel, its stashed away God knows where.

In shooting the M16a1 in Combat matches. (KD targets, 100, 200, 300, 400 yards) the Gun started out with a BSZ or sighted in at 250 yards (Actually it used meters). You shot straight on at 100 yards, point of aim. (Big target standing at 100 yards). Then you came DOWN I believe two clicks on the front sight for 200, up three for 300, then went to the "L" sight for 400 yards.

What happens, when you have a 250 yard BSZ, the bullet is still climbing at 200 yards, crossing 250 on its way down, come up again at 300 with the sights, then use the L sight to bring it up for 400 yards.

When I shot these matches, I just used the 250 BSZ and didnt touch the sights. I shot straight away at 100 (that close it didnt matter on that target), took a six o'clock hold at 200. and center hold at 300, and frame or navy hold at 400. Worked great for me.

I do the same in Multi gun matches. BSZ, shoot straight on. Normally the targets are big enough that you can head shoot the target up to 400 yards. Even at 400, the M193 (or its equilivent) dosnt drop that far at 400 to give you a miss. I use a SP1 for these matches saving my White Oak for High Power.

In Appendix A of the USAMU Counter-Sniper guide explains this quite well in its recommendations for LE Counter snipers using the 223 Bolt gun for civilian LE.

What they were explaining, is one can use the Army's BSZ on the Bolt gun, and be able to make head shots, aming at the mouth of the target, out to 300 yards.

This worked as AMU said, in the 223 bolt gun I carried in LE.

I cant explain it very well, but if one is interested I'd recommend he consult the USAMU Counter-Sniiper guide.

[mapsjanhere]

The Y max denotes the highest point of your trajectory, in your example it is somewhere between the 1.45 at 100 (still rising), reach the 1.61 at maybe 120, start dropping to 1.34 at 150 and be down to 0 at 200.
The only time this would be of importance is if you'd have a really long tunnel to shoot in, and you're trying to figure out how far out you can shoot without hitting the ceiling. My range has a 100 yard long 12" tunnel to shoot without wind influence, so I might be able to find out if I can sight my Marlin 1984C with 38 special rounds at 100 yard. For real flat shooting rifle rounds it clearly wouldn't matter.

[zippy13]

CPT Kraig,
I don't think it's so much that the M193 is a funny creature. I suspect that it has to do with the height of the A1's sights above the bore. There's the old rifleman's trick: if you want a longer point blank range, elevate your sights -- that way it takes the bullet longer to first cross the line of sight.
Just curious, what was the height of the sights in the bolt gun you used as compared to the A1?

[kraigwy]

Ref: Funny Creature, I was being scarcastic.

The M193 isnt doing any thing any other bullet doesnt do, its how we correct for a given BSZ, and apply it to other applications thats differant.

The sight hight of the A1 is about 1 inch higher then my (Reming 700 223) bolt gun.

The differance is compinsated for by using a six oclock hold with the A1, vs. point of aim or center mass with the glass on the bolt gun. (as it was explained to me by the AMU, and seems to work with my guns).

In this case, you get the same results, ref. head shots to 300 yards.

[mapsjanhere]

Played a bit with it, it could be of importance in some rare cases of long distance hunting. At 600 yards a 223 will rise 4 ft above your line of sight. So if you have a tree at 300 yards you might be aiming clearly under it, but your bullet might hit branches anyway.

[diensthunds]

Here's the thing though, the only real reason I was even interested in the software is so that: 1. I can input the data I have for a given load, ie. I get a "recipe" for a load from say hodgon's web site, plug in the data to the software and get a reasonable idea of what the bullet is doing at given distances so I can then go out and shoot the rounds having an idea of where they should be impacting on the target. 2. Figure out via a lot less expense what rounds will work best for my weapon rather then having to buy a ton of ammo (by that I mean various bullet types, powder charges, primers, etc) that may or may not provide decent results. Now granted the software gives theoretical results and actual shooting gives well actual results and I know the 2 may not be exactly (and probably won't be) the same but if the theoretical gets me close then I'll be happy to start there.

[RKG]

The only time this would be of importance is if you'd have a really long tunnel to shoot in, and you're trying to figure out how far out you can shoot without hitting the ceiling.

Actually, the function of "Max Y" (or "Mid-Range Trajectory") is to give guidance as to whether, at the selected zero, it would be necessary to calculate a hold under, given the size of the kill zone of the target at which you are shooting.

[Bud Helms]

Will the software let you set the sight-in zero at the muzzle? If so, the drop at any distance from the muzzle will equal to the total drop at that same range. No?

[diensthunds]

The only thing I can set is the scope height and as low as I can get that is 0.001". Even setting that the total drop at say 250 yards is still 13.22 even though the graph shows the trajectory of the flight path as intersecting at 0" this is why I don't understand the data given as compared to the graph plotted.

[zippy13]

Let's take a simple look at the 250 yard graph without worrying about the numbers, let's concentrate on the concept: The graph's horizontal "zero line" is the sighting line. The curved red line is the path of the bullet. So far, so good?

Disregarding air resistance, when we shoot a bullet, from the instant it leaves the muzzle it's being pulled toward the earth by gravity. We need to adjust our aim to compensate for the fall due to gravity. If we were bore sighting the gun, we'd simply aim high equal to the distance the bullet will fall. The same principal we use when shooting a arrow from a bow. In a bore sighting condition, the red curve would start at the 0, 0 point of the graph.

But we're not using bore sighting. By necessity, our sights are above the bore. So, when we aim high to compensate for the fall of gravity, we must take into consideration the hight of the sights above the bore. Suppose the bullet falls 6-inches before it reaches the target range and your sights are 2-inches above the bore. If you bore sight you'll have to aim 6-inches high; but, if you use the sights you'll have to aim 8-inches high to hit the same spot. Hopefully this makes sense to you.

Next we'll take a look at the confusing "total" drop. You'll have to look beyond the graph to understand this. It's how much the bullet falls with respect to the bore's alignment. I've extended a blue line to indicate the bore alignment. The height of this line above the bullets trajectory is the total drop (I show the 250-yd total drop).

I hope this clarifies things for you.

[mapsjanhere]

As for the significance of the number, if your gun was boresighted, or you're using a laser that runs parallel to the bore, this is how high you need to aim over the target to hit.