Shooting theory question

[The1970's]

So I was visiting a friend today and we started playing around with one of those laser trainers to see who could get the fastest draw, fastest "reload", etc. I started noticing that standing 10 yards away my semi auto was shining the laser about 2" high when the sights were held on the bullseye. Well that got me curious so I moved closer and eventually I determined that it was shining dead on at about 2.5 yards. It was low if I moved closer and higher if I moved further away.

As a mental exercise I tried to remember a couple ballistic calculations that I had learned years ago. I eventually determined that if that trend continued, my laser would shine almost 6" high at 25 yards and about 1 foot high at 50 yards. But here's the problem: assuming an average speed of 1150 fps, a 9mm will only drop a little under an inch at 25 yards. But...I have no problem hitting the target when i'm shooting live ammo, and my point of impact is damn near perfect with the point of aim. So I must have done something wrong. I just can't seem to figure out the issue. Any help?

Sorry for the overly technical question, I wasn't sure which board was most appropriate but I figure someone must know

[Winger Ed.]

Those things might not line up perfectly at a given range that jives up with your bullet drop & 'zero'.

You'd need to live fire it to check. But I wouldn't expect them to be as accurate/on target as a high end bore sight.
See where the dot is in relation to your sight picture at the different range, and shoot accordingly to find where its zeroed,

or more nearly where the two points are in a bullet's arc of flight that 'point of aim' is the same as 'point of impact'.

[dtknowles]

Sights at most can be dead on at two ranges. With sights above the barrel, the bullet will rise above the line of sight at some point on the trajectory, at that point the sights are dead on. Eventually the bullet will fall below the line of sight and will be dead on again. With a pistol more so than a rifle the barrel moves between the time you press the trigger and when the bullet leaves the barrel. With a centerfire pistol the barrel will be pointing higher when the bullet leaves the barrel.

You don't say where the laser is but I am guessing it is in the barrel. If you take it out spin is 90 or 180 degrees and put it back in does it shift relative to the sights? I wonder if it is perfectly centering in the bore.

Tim

[The1970's]

Yes but with the laser trainer the sights will only be right on at one point, because it essentially simulates a bullet with no drop. That point seems to be right at about 2.5 yards. And yes the laser cartridge goes in the chamber. It has a couple of O-rings that hold it relatively tightly and keep it fairly accurate. I have taken it out and put it back in several times and never noticed a difference in where it was shining. I'm sure it's not as accurate as a high quality bore sight, but its not bad.

[Conditor22]

I'm not the sharpest tack in the sewing box but to my understanding, boolits/bullets don't start falling for 25 to 50 yards.

Question 2 why would you even need sights at 2.5 yards? much less site in at that distance [smilie=s:

[wv109323]

Unless you have hands of steel, your grip is not a solid rest for the pistol. Your point of impact will change between a tight or loose grip.

[The1970's]

This wasn't exactly a project of practicality. I know there's really no use of using sights at that short of distance, and that the laser is not going to do what a live round will do. I'm just trying to figure out why my math doesn't add up. The laser shoots 2.5" high and the bullet will only drop less than 1/4" inch at that distance. Yet I hit dead on during live fire. So clearly i've done something wrong in my theory and I just can't figure it out

[Winger Ed.]

The laser shoots 2.5" high and the bullet will only drop less than 1/4" inch at that distance.

Your math will only work if the sight plane is 100% level and parallel to the center line of the bore.
The laser doesn't know how to compensate for that, or bullet drop.

Try laying the gun down flat on a table or in a rest, turn on the laser, and put a straight edge over the sights as they are aligned.
Or, look through/over the sights with another laser.
I'm guessing you'll see the difference then.

[Brass&Lead]

LASERs are effectively a straight line while bullets travel in an arc. There are two points where the bullet crosses the line of sight. The first point is near the muzzle and the second point is at the target.
This is an example of 45ACP courtesy of https://www.federalpremium.com/ballistics-calculator
It shows a zero at 7 ft and 49ft
272557

[megasupermagnum]

You aren't wrong, my calculations also show a 9mm bullet will drop around 1" at 25 yards. My question though, is why do you think you pistol and the laser gun would be sighted in the same way? Your pistol is not zeroed at 2.5 yards, or you would be shooting over everything.

[JonB_in_Glencoe]

Be sure to include math formulas for your trigger pull and recoil/flinch ;)

[BK7saum]

The last place I would expect the bullet to hit is where a bore sighter or laser are pointing. barrel harmonics, recoil, grip, flinch, etc all come to play.

That is we zero rifles and pistols instead of relying on a laser in the chamber or muzzle. They will get you close, but i can almost guarantee that the bullet leaving the muzzle isn't following the laser path, discounting drop.

[BK7saum]

If you look at a revolver, a lightweight. snubnose, the barrel doesn't point toward the bullseye, but actually points downward by an observable amount.

[The1970's]

You aren't wrong, my calculations also show a 9mm bullet will drop around 1" at 25 yards. My question though, is why do you think you pistol and the laser gun would be sighted in the same way? Your pistol is not zeroed at 2.5 yards, or you would be shooting over everything.

Right. I know it's not zeroed at 2.5. It's more like 25. I guess my question is where does the laser differ from a theoretical "no gravity" bullet. Surely a bullet that does not experience the effects of gravity would not change my "zero" point to 2.5 yards, so why do I see that with the laser? I know that barrel harmonics and grip all come into play but I wouldn't expect that large of a difference.

For example, my math says a 9mm will drop 0.81" at 25 yards. So with the laser i.e. a "no gravity" bullet, I would expect to see it "hit" almost exactly .81" high. Instead it "hits" about 6 inches high. That's not a small difference at such a short range. I'm by no means the best shot around but I can certainly tell the difference between 3/4" and 6 inches.

[MUSTANG]

I'm not the sharpest tack in the sewing box but to my understanding, boolits/bullets don't start falling for 25 to 50 yards.

Question 2 why would you even need sights at 2.5 yards? much less site in at that distance [smilie=s:

Not quite true The boolit/bullet starts "Dropping" as soon as it leaves the end of the barrel due to gravitational pull. Because of the energy imparted from the gas of the powder burning the path the bullet takes is that it rises over the straight visual line and then fall below that visual line. All through that arc the bullet follows, it is being puled by gravity.

[JonB_in_Glencoe]

SNIP>>>

I know that barrel harmonics and grip all come into play but I wouldn't expect that large of a difference.
how much did your Math tell you, to expect?

[farmerjim]

32ft/sec^2

[Win94ae]

I usually sight my handguns in at 65 yards with my preferred load. So it hits POA around 7 yards, then is 4 or so inches high at 30 yards, hits POA at 65 yards, then is 4 or so inches low at 100 yards.

I have 2 38 specials with fixed sights that hit POA around 7 yards, but climb higher and higher as the range gets longer. By the time I get beyond 150 yards, I can't shoot them well enough to see at what range the round hits back to POA.

When I sight my handguns, I take note at what height my POI is when it comes back down, it will always be close enough at 7 yards.

[Win94ae]

LASERs are effectively a straight line while bullets travel in an arc. There are two points where the bullet crosses the line of sight. The first point is near the muzzle and the second point is at the target.
This is an example of 45ACP courtesy of https://www.federalpremium.com/ballistics-calculator
It shows a zero at 7 ft and 49ft
272557

Actually, that is yards, not feet.

[megasupermagnum]

Right. I know it's not zeroed at 2.5. It's more like 25. I guess my question is where does the laser differ from a theoretical "no gravity" bullet. Surely a bullet that does not experience the effects of gravity would not change my "zero" point to 2.5 yards, so why do I see that with the laser? I know that barrel harmonics and grip all come into play but I wouldn't expect that large of a difference.

For example, my math says a 9mm will drop 0.81" at 25 yards. So with the laser i.e. a "no gravity" bullet, I would expect to see it "hit" almost exactly .81" high. Instead it "hits" about 6 inches high. That's not a small difference at such a short range. I'm by no means the best shot around but I can certainly tell the difference between 3/4" and 6 inches.

Why wouldn't you believe recoil is the cause? By my calculations, with a 4" barrel, if you move the muzzle .027", you will move 6" at 25 yards.

[wv109323]

As soon as the bullet starts accelerating there is an opposite force back through the rigid firearm frame. That frame is held in your hand that is not rigid. Therefore according to your grip and wrist strength the pistol is moving while the bullet is accelerating. So POI is different from POA if the sights are aligned with the bore. Sights are used to align the POA to the POI.
Your calculations would be true if you could fire the pistol without the sights moving. Also the hammer fall may contribute to firearm movement.

[popper]

About the only thing those lasers are good for is seeing how steady you aim is. And helping trigger 'pull'.

[kerplode]

Not quite true The boolit/bullet starts "Dropping" as soon as it leaves the end of the barrel due to gravitational pull. Because of the energy imparted from the gas of the powder burning the path the bullet takes is that it rises over the straight visual line and then fall below that visual line. All through that arc the bullet follows, it is being puled by gravity.
This isn't right either...

Bullets start to drop immediately upon exiting the barrel.

Additionally, there are no dynamics (powder gasses, rotation, or otherwise) that cause the bullet to "rise" at any point along it's trajectory. The reason that it moves up relative to the LOS is that the axis of the bore is pointed up relative to the LOS. Basically, the bullet "rises" because your sights are set to fire the bullet into the air a little.

If you leveled your barrel, and ignored the sights, the bullet would begin dropping immediately upon leaving the muzzle and would continue to only fall until it struck the ground.

[The1970's]

Why wouldn't you believe recoil is the cause? By my calculations, with a 4" barrel, if you move the muzzle .027", you will move 6" at 25 yards.

Even if recoil was the cause of the difference I'm seeing. IT should move in the other direction. Since the barrel is above my grip, the muzzle flips upward, meaning that recoil should make the live fire POI higher than a laser with no recoil

[44MAG#1]

Here is a question I must ask. If your bullet impact with real ammo in a real gun is where it should be when you shoot the gun why would you be concerned where the laser trainer would point?
I sure wouldn't because I would be more concerned with real ammo results.

[megasupermagnum]

Even if recoil was the cause of the difference I'm seeing. IT should move in the other direction. Since the barrel is above my grip, the muzzle flips upward, meaning that recoil should make the live fire POI higher than a laser with no recoil

Again, why would the sights on your pistol have anything to do with the sights on a laser training gun?

[The1970's]

Again, why would the sights on your pistol have anything to do with the sights on a laser training gun?

Just to be clear, this is not a toy training pistol. It is my live handgun, the same one that I have no problem shooting, using one of those laser training cartridges. Something similar to this:

https://www.amazon.com/Pink-Rhino-Laser-Training-Cartridge/dp/B07K34W265


And to answer 44mag's question: It really doesn't matter where the laser hits. I can shoot the gun fine and I won't be changing my technique based on this discovery. It was just a question that came up among me and a friend that we could not answer. That's why I choose to post it in the discussion section.

So far the best explanation I have is that when firing live ammo, the barrel (somehow?) consistently ends up pointing downward from the sight picture between pulling the trigger and the bullet leaving the barrel. It can't be caused by trigger pull or grip, because those variables are accounted for in the laser as well. So either recoil or the barrel sliding slightly backwards (in a semi-auto) is to blame. Still seems odd and hard to believe to me. So I suspect there is another explanation

[44MAG#1]

It is one of those things I try not to think about unless it affects my shooting with real guns and ammo.

[megasupermagnum]

Just to be clear, this is not a toy training pistol. It is my live handgun, the same one that I have no problem shooting, using one of those laser training cartridges. Something similar to this:

https://www.amazon.com/Pink-Rhino-Laser-Training-Cartridge/dp/B07K34W265


And to answer 44mag's question: It really doesn't matter where the laser hits. I can shoot the gun fine and I won't be changing my technique based on this discovery. It was just a question that came up among me and a friend that we could not answer. That's why I choose to post it in the discussion section.

So far the best explanation I have is that when firing live ammo, the barrel (somehow?) consistently ends up pointing downward from the sight picture between pulling the trigger and the bullet leaving the barrel. It can't be caused by trigger pull or grip, because those variables are accounted for in the laser as well. So either recoil or the barrel sliding slightly backwards (in a semi-auto) is to blame. Still seems odd and hard to believe to me. So I suspect there is another explanation

Read the reviews, lots of people have them shoot to different places. The laser is not perfectly centered with the barrel.

[JonB_in_Glencoe]

SNIP>>>

It can't be caused by trigger pull or grip, because those variables are accounted for in the laser as well.
Don't discount trigger pull so quickly.
Have you ever done the flinch test?

[C.F.Plinker]

You have two straight lines that intersect around 8' from the muzzle. One line is the line of sight from the rear sight across the front sight and on to the target at whatever distance it is from the muzzle. The other line is the beam from the laser. Let's imagine that the barrel is horizontal and the laser beam is also horizontal. If the front sight and rear sight were both the same distance above the barrel centerline the line of sight would also be horizontal. And the laser beam would be about 3/4" below the line of sight at all distances. It's not. The two intersect around 8' out. So the rear sight has to be higher than the front sight. That's no surprise since the gun has been sighted in. The line of sight is now headed in a downward direction. It is above the ler beam out to 8' and below the laser beam past 8'. Or the laser beam is below the line of sight out to 8' and above the line of sight past that. When we go from 8' to 10 yards (30') , a distance of 22', the laser beam rises 2" or about 10% of the distance from the crossover point. Likewise at 25 yards (75 feet) the laser is about 6" high which is also about 10% of the 67' from the crossover point. Same with the 12" rise at 50 yards. Yea, I had to get out the pencil and paper and sketch this out too.

If you are using the laser to make your initial sight adjustments, just get them to match at some distance where you can still see the laser dot just over the front sight. You will be on paper at that distance. Now load real cartridges and get it sighted in for that particular load and the way you shoot at the distances you usually shoot at.

[44MAG#1]

It is hard for me to wrap my head around this.

[The1970's]

Yea, I had to get out the pencil and paper and sketch this out too.

If you are using the laser to make your initial sight adjustments, just get them to match at some distance where you can still see the laser dot just over the front sight. You will be on paper at that distance. Now load real cartridges and get it sighted in for that particular load and the way you shoot at the distances you usually shoot at.

You did the same sketch I did and came up with the exact same numbers so it's probably safe to say that we both did it correctly. Let's stick with that 6" at 25 yards...my factory ammunition gives me velocity information out to 25 yards. So I can easily calculate the bullet drop at 25 yards to be around 0.8". 6" of bullet rise minus 0.8" of bullet drop = 5.2" above the point of aim. The problem is that I know with this ammo in my gun that the POA and POI are virtually identical at 25 yards. So there must be an explanation for that 5.2" difference.

I would attach a photo of my sketch for others to see but the site keeps saying "upload failed".

Edit: I was able to replicate my math with one of the online shooting calculators by setting the zero distance at 2.2 yards. They calculate a chart with a horizontal line representing the sight line. The chart should be viewable at this link: http://www.shooterscalculator.com/ballistic-trajectory-chart.php?pl=%5BPreset+Name%5D&presets=&df=G1&bc=0.140&bw=115&vi=1200&zr=2.2&sh=0.556&sa=0&ws=0&wa=90&ssb=on&cr=100&ss=1&chartColumns=Range%7Eyd%3BElevation%7Ein%3BElevati on%7EMOA%7EFBFFF5%3BElevation%7EMIL%3BWindage%7Ein %3BWindage%7EMOA%7EFBFFF5%3BWindage%7EMIL%3BTime%7 Es%3BEnergy%7Eft.lbf%3BVel%5Bx%2By%5D%7Eft%2Fs&lbl=%5BChart+Label%5D&submitst=+Create+Graph+

[The1970's]

Don't discount trigger pull so quickly.
Have you ever done the flinch test?

I have done the flinch test. It's typical for shooters to train to avoid flinching during the trigger pull, right? It's hard for me to believe that a gun manufacturer would so consistently rely on the flinch of a shooter that they set the sights accordingly. Every pull of the trigger would require the exact same flinch to produce consistent results if that was the case.

[Dukeconnor]

the laser is probably out of alignment

[JonB_in_Glencoe]

Yes but with the laser trainer the sights will only be right on at one point, because it essentially simulates a bullet with no drop. That point seems to be right at about 2.5 yards. And yes the laser cartridge goes in the chamber. It has a couple of O-rings that hold it relatively tightly and keep it fairly accurate. I have taken it out and put it back in several times and never noticed a difference in where it was shining. I'm sure it's not as accurate as a high quality bore sight, but its not bad.

O-rings, Huh.
while that may seem like it's seated and centered in the chamber, maybe there is some influence on the trainer from the extractor or the bolt.

[C.F.Plinker]

Our calculations are based on the sights and laser being in agreement at 2.5 yards. Could you tape a piece of graph paper on a wall, then clamp the barrel down to a table about 2.5 yards away? ( plus or minus, more or less ) Put the laser in the barrel and mark the point on the paper where the dot appears. now rotate the laser 90 degrees and repeat. Also at 180 and 270 degrees from the original position. We are probably looking for changes of less that 1/2 inch. If there is a spread, multiply that by 10 and that is the variance you could see at 25 yards due to changes of the laser position within the barrel.

P.S. I got on the website you linked to above and ran calculations for a 25 yard zero. There was no near and far zero. Just the one zero with distances greater or less than 25 yards having an impact point below the line of sight. So 25 yards is where the trajectory is tangent to the line of sight. Similar things happen to 22LR at 50 or 60 yards and to .223 at 100 yards using the sight height of an AR.

[The1970's]

So I finally set up a test on the bench. I clamped my barrel down (just the barrel, no slide or sights) and set up a paper 80 inches away (that's the longest I could get on my bench. Marked the laser, fired, rotated laser 90 degrees, then continued doing that for a full rotation. Each time I made a dot on the paper where the laser hit. Measuring those dots I get a maximum elevation difference of 0.200"...a fair bit of slop in the laser, but still not enough to be the sole cause of what i'm seeing

[C.F.Plinker]

Thank you for taking the time to do that. The 0.20 inch variation at 80 inches works out to be about 2.25 inches at 25 yards which is about a third of what we calculated. Why the difference? How about real world dynamics? Or the difference between theory and practice. The posters above have given many things that can be affecting where our shots go.

If someone offers to let me shoot their gun I don't expect my group to go where their's goes because my grip, sight picture, and trigger squeeze are different. Lately I have been using a fixed sight revolver. With a one hand grip firing single action the group will be on the left side of the bull. Firing double action with a two handed grip the group will be on the right side of the bull and about 1-2 inches lower.

The laser is showing you where your shots could go (within 2" or so) if the world was perfect. It's not. That's why there are adjustable sights on many guns. They allow us to get the gun to fit our individual way of shooting and to let us aim at one place on the target and hit in another place if we so desire.

Thanks again for making these measurements.