Ballistic path information?

[ummm]

I'm a novice who thinks learning about the ballistic path of my bullets might help my shooting. Hoping for your help.

So I sighted in my pistol indoors at 25 yards, got (for me) a really nice (supported) zero. Transitioned with that zero to 10 yards (supported also), and was consistently 1.5 inches low.

Confusion is because the online ballistic calculators tell me this is not the behavior I should be seeing, so I'm hoping one of you can tell me where I can find accurate ballistic path info, or school me in using the online ballistic calculators correctly.

I took cartridge data from the Speer website (9mm TMJ 124 gr Lawman), so I'm guessing it's pretty accurate, and I measured the height of my sight above the center of the barrel to be half an inch, almost exactly. The target is about the same height as the gun, so I think that's about a 0 degree shooting angle.

The graph from the ballistic calculator looks like this:

and here's the data used to create the chart:

shooterscalculator.com data for Speer Lawman 124gr 9mm / XDm 5.25

According to their chart, I should only be a fraction of an inch off at 10 yards, but I'm 1.5 inches off.

I just want to get an accurate representation of what the bullets are doing. If I had access to an outdoor range and 100 target stands I would do it "for real", but I don't

Edited June 8, 2012 by ummm

[PistoleroJesse]

Hard to say, but first thing I would do is get more accurate velocity than what's on the box.

Use a chrono.

[Hi-Power Jack]

Ummm, the problem might be that if you fire a five shot

group at 25 yards, it tends to be 2 - 4" in diameter.

So, when you say you have a nice sight in for 25 yards,

you probably mean that you have a nice circle of bullet

holes, some of which are a little low, some a little high,

some a little to the left and a few to the right.

My guess is that if you were to fire 3 more 5-shot groups,

you'd find that the group size increases, and you'd have

even more shots low, left, right & high.

So part of the problem is that you don't aim your gun at

25 yards and find five bullets hitting the exact center

of the bullseye - but have a dispersion of ___ inches (you

fill in the blank, depending on your gun, your ammo, and

your ability).

Now, at ten yards, you fire a five shot group, and it's a

lot smaller group than at 25 yards, but it tends to be

low by 1.5" (some are actually .5" low, and some left,etc.)

Why not try firing a 15 shot group at each distance, and

eliminating the 3-4 shots that are obvious "flyers" - see

where the center of the groups are - see if they are

closer together at the two distances.

Also, a 1.5" difference is very small for most pistol

shooting scenarios - especially the action sports.

Have you tried it at 50 yards? According to your chart,

there shouldn't be too much difference, once again.

[HoMiE]

Your line of sight isn't going to be perfectly parallel to your barrel either so that is why it's lower, or at least that's the way I understand it. When I shoot at 50yd targets with sights, I am actually aiming at the lower A/C line becasue my guns will shoot high at 50yd with a 25 yd zero. I can remember the frustration when first sighting in aiming at upper A/C line thinking my bullet will drop with gravity and I was shooting over target.

Edited June 8, 2012 by HoMiE

[Powder Finger]

It does drop with gravity, the instant it leaves the barrel.

[HoMiE]

It does drop with gravity, the instant it leaves the barrel.

Not if the trajectory is on a slighlty upward path.

Gravity is in effect the instant it leaves barrel, but it does not necessarily "drop". Sae thing as shooting an arrow in an upward arc. It goes up past line of sight, till the upward gravity is greater then it goes back down, past line of sight, then finally till it touches ground zero relativley speaking.

[DoubleL]

It does drop, once it reaches the 'top' of it's flight path. From what I have gathered the most important factor is understanding that the gun may appear to have a level, or zero degree, rise; the barrel, however is tilted within the housing of the pistol or slide to always add a fixed amount of rise to your aiming geometry. I have learned that it's nice to have a rudimentary understanding of the physics behind bullet trajectory but the most important thing to know is how YOUR hold, stance, grip, eyesight etc. effect the POI vs. POA for your desired distances.

Shoot groups at set distances and plot your results. All the physics in the world won't change how the gun handles and hits in YOUR hands. Once you know where to aim for any given distance, you can put hits at any given distance. Keep in mind that benchrested groups rarely match your freestyle groups.

Recoil and unlock times have been beat to death in many threads here. I too thought along the same lines as you. After only a few practice sessions I came to the conclusion that the best way to understand it is to go shoot from 3 all the way out, to whatever, rifle range if need be. It's really the only way to know for sure what your shooting does to the "math" of bullet trajectory and flight path.

[LRRP]

As soon as a bullet leaves the support of the barrel it has a downward gravitational force on it, regardless of trajectory. Depending on the slant of the barrel the gravitational force will vary. With the highest force being when the barrel is flat the least when the barrel is angled up, but none the less it has a pull down.

[HoMiE]

As soon as a bullet leaves the support of the barrel it has a downward gravitational force on it, regardless of trajectory. Depending on the slant of the barrel the gravitational force will vary. With the highest force being when the barrel is flat the least when the barrel is angled up, but none the less it has a pull down.

Gravity is always constant. The trajectory path will vary depending on the angle of the axis of the bore.

[LRRP]

As soon as a bullet leaves the support of the barrel it has a downward gravitational force on it, regardless of trajectory. Depending on the slant of the barrel the gravitational force will vary. With the highest force being when the barrel is flat the least when the barrel is angled up, but none the less it has a pull down.

Gravity is always constant. The trajectory path will vary depending on the angle of the axis of the bore.

Gravity does stay constant. I agree. But the effect of gravity will vary depending on the angle of axis of bore. You are correct the gravitational "force" will not vary, but will not the rate of the bullet drop vary?

[ummm]

Why not try firing a 15 shot group at each distance, and

eliminating the 3-4 shots that are obvious "flyers" - see

where the center of the groups are - see if they are

closer together at the two distances.

This sounds good, but I'm not sure about the last sentence -- what do you mean by "closer together at the two distances"?

After only a few practice sessions I came to the conclusion that the best way to understand it is to go shoot from 3 all the way out, to whatever, rifle range if need be. It's really the only way to know for sure what your shooting does to the "math" of bullet trajectory and flight path.

OK, so you're saying that I'm the influence causing my shots to differ so wildly from the chart? I can get behind that idea. Certainly reality is the best test. I'll just shoot groups at every distance my local range has to offer, and make my own graph that way. It's just a lot more work than plugging in some numbers online

[HoMiE]

As soon as a bullet leaves the support of the barrel it has a downward gravitational force on it, regardless of trajectory. Depending on the slant of the barrel the gravitational force will vary. With the highest force being when the barrel is flat the least when the barrel is angled up, but none the less it has a pull down.

Gravity is always constant. The trajectory path will vary depending on the angle of the axis of the bore.

Gravity does stay constant. I agree. But the effect of gravity will vary depending on the angle of axis of bore. You are correct the gravitational "force" will not vary, but will not the rate of the bullet drop vary?

Gravity is Gravity is Gravity. All objects will always fall at the contast rate perpendicular to the surface of earth. Now fall is relative to the bore axis so the bullet will never go above the muzzle height if you were to draw an imagine line that extended out the muzzle for infinity. The trajectory changes, but the vertical force is always the same force of gravity. The horizontal forces changes due to velocity slowing down because of drag.

[DoubleL]

Bullet drop always gets the crowd riled up.

[Hi-Power Jack]

Why not try firing a 15 shot group at each distance, and

eliminating the 3-4 shots that are obvious "flyers" - see

where the center of the groups are - see if they are

closer together at the two distances.

This sounds good, but I'm not sure about the last sentence -- what do you mean by "closer together at the two distances"?

Ummm, right now you're reporting that the groups are 1.5" apart at 10 and 25 yards.

I'd guess that with a larger sample, you won't find such a large distance - i.e. your 10 yard groups

will no longer be 1.5" lower than your 25 yard groups.

Also, try it again at 50 yards - see what happens - your group size will increase

(by quite a bit unless you have a very accurate gun/ammo/shooter), but I bet you'll

be surprised where those bullets hit - bet they're at least 6" off in one direction

or the other & I'm guessing they'll be quite a bit LOW.

We're dealing with the dot center of a fair size group - and calling that as precise,

but it isn't precise - we have to remember that being sighted "right on" at 25 yards

is actually a fairly large size - my old BHP with Remington ammo used to average 5-6" group

at 25 yards - and each group I fired was centered a little differently. That's when

I started shooting 15 shot groups, and eliminating the 3-4 shots that were "off".

But, for action sports, that seems to be okay (for a C shooter, anyway

After only a few practice sessions I came to the conclusion that the best way to understand it is to go shoot from 3 all the way out, to whatever, rifle range if need be. It's really the only way to know for sure what your shooting does to the "math" of bullet trajectory and flight path.

OK, so you're saying that I'm the influence causing my shots to differ so wildly from the chart? I can get behind that idea. Certainly reality is the best test. I'll just shoot groups at every distance my local range has to offer, and make my own graph that way. It's just a lot more work than plugging in some numbers online

[mda]

As soon as a bullet leaves the support of the barrel it has a downward gravitational force on it, regardless of trajectory. Depending on the slant of the barrel the gravitational force will vary. With the highest force being when the barrel is flat the least when the barrel is angled up, but none the less it has a pull down.

Gravity is always constant. The trajectory path will vary depending on the angle of the axis of the bore.

Gravity does stay constant. I agree. But the effect of gravity will vary depending on the angle of axis of bore. You are correct the gravitational "force" will not vary, but will not the rate of the bullet drop vary?

Gravity is Gravity is Gravity. All objects will always fall at the contast rate perpendicular to the surface of earth. Now fall is relative to the bore axis so the bullet will never go above the muzzle height if you were to draw an imagine line that extended out the muzzle for infinity. The trajectory changes, but the vertical force is always the same force of gravity. The horizontal forces changes due to velocity slowing down because of drag.

NO. Earths gravity is not constant.

It varies slightly depending were and and when you are and it changes slightly constantly. Look up Gravity Recovery And Climate Experiment (GRACE), a joint mission of NASA and the German Aerospace Center. NASA has been measure earth surface gravity for a number of years. Some interesting graphics.

MDA

[Guy Neill]

For the parameters entered, the trajectory should be accurate.

What is your supported position? Arms supported, or gun supported?

If you are truly zero at 25, there should be no possibility of the gun delivering the bullet 1.5" low at 10 yards. If so, the bullet could never rise to be zero at 25 yards. Are you, perhaps, looking over the sights at the target at the closer range? Milking the grip as also capable of causing low hits, but is the gun is supported, there is little likelihood of that being the cause.

As I understand your description, all shooting was indoors, is this correct? Thus, the lighting should not have materially changed.

Even though gravity does vary, that is not the cause of the discrepancy seen here.

Try having another shooter shoot the gun and ammunition and see if they get the same results.

Other than lighting, milking or looking over the sights, i cannot think of an explanation for your results. I'll be very interested in discovering the reason.

Guy

I'm a novice who thinks learning about the ballistic path of my bullets might help my shooting. Hoping for your help.

So I sighted in my pistol indoors at 25 yards, got (for me) a really nice (supported) zero. Transitioned with that zero to 10 yards (supported also), and was consistently 1.5 inches low.

Confusion is because the online ballistic calculators tell me this is not the behavior I should be seeing, so I'm hoping one of you can tell me where I can find accurate ballistic path info, or school me in using the online ballistic calculators correctly.

I took cartridge data from the Speer website (9mm TMJ 124 gr Lawman), so I'm guessing it's pretty accurate, and I measured the height of my sight above the center of the barrel to be half an inch, almost exactly. The target is about the same height as the gun, so I think that's about a 0 degree shooting angle.

The graph from the ballistic calculator looks like this:

and here's the data used to create the chart:

shooterscalculator.com data for Speer Lawman 124gr 9mm / XDm 5.25

According to their chart, I should only be a fraction of an inch off at 10 yards, but I'm 1.5 inches off.

I just want to get an accurate representation of what the bullets are doing. If I had access to an outdoor range and 100 target stands I would do it "for real", but I don't

[ummm]

For the parameters entered, the trajectory should be accurate.

What is your supported position? Arms supported, or gun supported?

If you are truly zero at 25, there should be no possibility of the gun delivering the bullet 1.5" low at 10 yards. If so, the bullet could never rise to be zero at 25 yards. Are you, perhaps, looking over the sights at the target at the closer range? Milking the grip as also capable of causing low hits, but is the gun is supported, there is little likelihood of that being the cause.

As I understand your description, all shooting was indoors, is this correct? Thus, the lighting should not have materially changed.

Even though gravity does vary, that is not the cause of the discrepancy seen here.

Try having another shooter shoot the gun and ammunition and see if they get the same results.

Other than lighting, milking or looking over the sights, i cannot think of an explanation for your results. I'll be very interested in discovering the reason.

Guy

Thanks, Guy. Arms supported, and yes, indoors.

OK, so it seems you experienced shooters are inclined to believe it's my fault, and that makes me happy, because I can get my head around that. What is milking the grip?

[Guy Neill]

Milking is when you squeeze your entire hand instead of just the trigger finger.

Guy

[Joe4d]

You are shooting a pistol, not a revolver. The barrel isnt attached to the sight. Your sights are not parallel to the axis of the bore and I seriously doubt the front and rear sight are the same height. That chart is only gonna work if the front and rear sights are exactly parallel to the bore.

zero dead on at 15 will put you almost on at 10 and 25.

[Hi-Power Jack]

You are shooting a pistol, not a revolver. The barrel isnt attached to the sight. Your sights are not parallel to the axis of the bore and I seriously doubt the front and rear sight are the same height. That chart is only gonna work if the front and rear sights are exactly parallel to the bore.

zero dead on at 15 will put you almost on at 10 and 25.

+1 But, from what I've seen (Many decades:(

you are much better off sighting in at the longest

distance you can - 30 - 50 yards.

Then see where you are at 10 & 25 yards.

That usually works a lot better than sighting in

for 10 yards and estimating where you'll be at

45 yards - just doesn't work very well.

[ummm]

You are shooting a pistol, not a revolver. The barrel isnt attached to the sight. Your sights are not parallel to the axis of the bore and I seriously doubt the front and rear sight are the same height. That chart is only gonna work if the front and rear sights are exactly parallel to the bore.

zero dead on at 15 will put you almost on at 10 and 25.

Thanks, Joe4d

So it's only a revolver chart? I have a lot to learn. Why don't pistol mfr's make their sights parallel to the bore? Is there some advantage?

+1 But, from what I've seen (Many decades:(

you are much better off sighting in at the longest

distance you can - 30 - 50 yards.

Then see where you are at 10 & 25 yards.

That usually works a lot better than sighting in

for 10 yards and estimating where you'll be at

45 yards - just doesn't work very well.

Thanks again, Jack. It seems to matter less and less at which distance I choose to zero, and matter more what effects I'm having on the gun. Is it reasonable to take this approach:

1) choose new zero distance

2) practice w/pistol, see effects

3) if displeased with results, go back to step #1

Or is there a better approach?

[Guy Neill]

The chart is for that projectile (any projectile with that BC), at that muzzle velocity and line of sight - regardless of gun.

Guy

[DoubleL]

Guy makes a good point right there. Ballistic charts erase all other factors on the flight of the bullet and focus on just ballistics. Hence the name ballistic chart

After you make it to your range and do some test shooting you'll probably see that your zero, unless it's WAY off, does not have the largest impact on your accuracy. Bad technique can and will change your accuracy massively more than a zero that's off by an inch or two at 20. Although tuning your zero to your eyes and your shooting is nice, once you know the sights on a given pistol if your technique is solid your accuracy should be too. To an extent at least. I personally learned the most while trying much longer than normal distances. The distance will greatly magnify any trigger issues you may have. A slight jerk at 3 is off by an inch or three. Same jerk on a 2'x2' target at 100 feet will fly feet wide! Plus it's fun to try and hit 2 liter bottles at what would be considered close rifle distances. The flight path is also easier to understand when you stretch your distance. Let's you physically see how much of a hold, if any, you need. I was amazed at how flat 9mm shoots. 100 feet the drop was not nearly what I was expecting.

[Hi-Power Jack]

Umm, the chart, and most of our experience here (I believe?)

suggests that if you sight the gun in at 15, 30 or 50 yards,

it should hit within 2" more or less at any other reasonable

handgun distance.

My experience is that if all your shooting is 25 yards or under,

sight it in at 15 or 25 yards and you'll be fine - BUT, if you

ever have a shot at 45+ yards - believe me, you won't know

where the bullets are going to land.

That's why, IMHO, it is better to sight in the gun at the

furthest distance you can - then you'll be sure that it's

also sighted in for 10 and 25 yards.

By the way, you've never mentioned what gun you're shooting,

or what you're doing with it? IPSC? IDPA? Bianchi?

And, I don't believe you've ever mentioned what size groups

you're getting at 25 or 15 yards?

[ummm]

By the way, you've never mentioned what gun you're shooting,

or what you're doing with it? IPSC? IDPA? Bianchi?

And, I don't believe you've ever mentioned what size groups

you're getting at 25 or 15 yards?

Jack,

It's for USPSA + IDPA.

I'm not sure how to measure group sizes, but my best (slow fire) unsupported groups at 25 yards are when I can cover all 5 shots with a coffee cup, even if the center of the group isn't always where I'm aiming. That doesn't usually happen -- maybe one group in three. I haven't tried 15 yard groups yet -- this thread was the first time I've bumped into that idea.

Then gun is much, much better than I am -- it's a Springfield XDm 5.25" with a Bar-Sto match barrel that was custom fit by the guys at Powder River Precision.

I guess I'm just a lazy shooter looking for a shortcut. There's a lot to remember in IDPA / USPSA -- how's my grip, don't slap the trigger, was my reload plan to reload after this target? etc, etc. Having to get a sight picture and then also factor in, "Well, this distance is not where I zeroed, so I should adjust my POA by..." is another burden I was hoping not to carry by finding a zero that kind of worked for most common USPSA distances.

I know there are long-distance (by handgun standards) classifiers, but they don't have other complications like movement, cover, reloading on the clock, etc, so then my mind would be able to focus only on sight picture and trigger control.

Looking forward to trying out groups at 15 yards -- thanks again!