Ballistic calculator with negative sight-over-bore?

[lucusloc]

So I am setting up a new rig and am playing with a new laser sight. It sits 2 inches below the barrel and I wanted to play with different zero ranges for it (mostly to figure out what the longest +2 to -2 zero point is). Unfortunately my calculator of choice (Hornady) does not do negative sight-over-bore measurements. A spot check of a few others (Shooters, Federal) shows they do not do negative numbers either. Do the wonderful and intelligent people here know of a calculator that does negative sight-over-bore numbers? Maybe something specific to lasers, or some other niche application?

Shooters does do negative SoB. I must have made another error that caused the calculator to fail. Got my calculations done. Details below.

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[NeoBlackdog]

Can't you just set it up for +2 and then subtract 4 from your final figure?
(That's a wild stab at it! I know nothing about these things!)

 

[TTSX]

Mental math is a thing. Just take whatever they say zero/50/100 etc is, then subtract 2 from that number.

 

[Koda]

Do the wonderful and intelligent people here know of a calculator that does negative sight-over-bore numbers?

You can put a negative value in the sight height on this one.

ShootersCalculator.com | Ballistic Trajectory Calculator

Calculates the ballistic trajectory of a bullet fired from a rifle, handgun or other firearm. Produces a ballistic trajectory chart and table that shows the drop, velocity, kinetic energy, windage, and trajectory of a bullet.

shooterscalculator.com

 

[lucusloc]

Can't you just set it up for +2 and then subtract 4 from your final figure?
(That's a wild stab at it! I know nothing about these things!)

No, funny things happen when you cross the zero line. For example, most standard zeros have two places where the bullet crosses the sight line, one rising and one falling. But with a negative SoB you can only ever have one, and it will be a "falling" crossing even if the bullet is still technically rising.

 

[lucusloc]

You can put a negative value in the sight height on this one.

ShootersCalculator.com | Ballistic Trajectory Calculator

Calculates the ballistic trajectory of a bullet fired from a rifle, handgun or other firearm. Produces a ballistic trajectory chart and table that shows the drop, velocity, kinetic energy, windage, and trajectory of a bullet.

shooterscalculator.com

I tried shooters, it failed to output anything when I used a negative number. It did not trow an error either, so I just assumed it failed because of the negative. I will give it a try again.

 

[NeoBlackdog]

No, funny things happen when you cross the zero line. For example, most standard zeros have two places where the bullet crosses the sight line, one rising and one falling. But with a negative SoB you can only ever have one, and it will be a "falling" crossing even if the bullet is still technically rising.

(Slaps forehead) Duh! Of course!

 

[TTSX]

So if your bore is +2 over your laser and you want to find out how far it'll go before getting to -2, can't you just figure what the bullet drop is and see how long it takes the bullet to fall 4 inches with a zero point of zero yards? Because if the bullet will only break the laser's plane once, then it can't ever get to more than +2 assuming the barrel and laser are exactly level with each other. If the laser is adjustable for elevation... I don't know how to do that one off the top of my head

 

[Koda]

I tried shooters, it failed to output anything when I used a negative number. It did not trow an error either, so I just assumed it failed because of the negative. I will give it a try again.

It works. You also have to give it a zero point like 100yds.

 

[lucusloc]

So if your bore is +2 over your laser and you want to find out how far it'll go before getting to -2, can't you just figure what the bullet drop is and see how long it takes the bullet to fall 4 inches with a zero point of zero yards? Because if the bullet will only break the laser's plane once, then it can't ever get to more than +2 assuming the barrel and laser are exactly level with each other. If the laser is adjustable for elevation... I don't know how to do that one off the top of my head

I mean, if I wanted to do all the math myself I would not be using a calculator in the first place

Also, you can get to more than +2 if you sight your laser low enough (far enough out). The question is if you will be able to see it (mine has a stated range of about ~150 yards). But, for example, if you have a bullet that drops 500 inches at 500 yards from a level barrel, and you sight your laser out to that 500 yard impact point, at some point along that trajectory you bullet will be hundreds of inches above the laser line. Not the full 500, but a lot more than 2.

 

[Koda]

It sits 2 inches below the barrel and I wanted to play with different zero ranges for it (mostly to figure out what the longest +2 to -2 zero point is).

What caliber, bullet, muzzle velocity and BC?

 

[lucusloc]

It works. You also have to give it a zero point like 100yds.

I did get it to work. Not sure what I messed up the first time, but I got it to give me a graph when I tried again. This will work for my needs. Thanks for pointing that out.

 

[TTSX]

I mean, if I wanted to do all the math myself I would not be using a calculator in the first place

Also, you can get to more than +2 if you sight your laser low enough (far enough out). The question is if you will be able to see it (mine has a stated range of about ~150 yards). But, for example, if you have a bullet that drops 500 inches at 500 yards from a level barrel, and you sight your laser out to that 500 yard impact point, at some point along that trajectory you bullet will be hundreds of inches above the laser line. Not the full 500, but a lot more than 2.

Right. I'm just assuming on a level laser for armchair quarterback math.

Adding angles to this stuff is just as bad as when they started adding letters to the numbers in algebra

 

[Koda]

I did get it to work. Not sure what I messed up the first time, but I got it to give me a graph when I tried again. This will work for my needs. Thanks for pointing that out.

For it to be accurate, you will need to input the questions I asked above, also your elevation.

Im curious what caliber and how far out does it go until it crosses your -2" line of sight?

 

[lucusloc]

For it to be accurate, you will need to input the questions I asked above, also your elevation.

Im curious what caliber and how far out does it go until it crosses your -2" line of sight?

I'm working on my new 10mm PCC build. I already have the optic sight zero set, but I just got the new under-barrel laser light yesterday and want to figure out the optimal use for that. I am using a generic 10mm load that is a hodgepodge of data I can find online. It does not need to be exact until I decide on a load I actually like with this platform. My number are BC .16, velocity 1140fps, weight 200grn. I am trying laser zeros from 5 yards to 100 to see what the point blank ranges look like.

I would probably be done by now, but I am sh*ttalking in other threads. Priorities you know.

 

[Koda]

My number are BC .16, velocity 1140fps, weight 200grn. I am trying laser zeros from 5 yards to 100 to see what the point blank ranges look like.

Your PBR zero is 50yds where your bullet would project flat and never arc more than the 2" above the line of sight. Your max range of -2" drop is about 60yds.

Note: you can bookmark your results...

ShootersCalculator.com | Ballistic Trajectory Calculator

Calculates the ballistic trajectory of a bullet fired from a rifle, handgun or other firearm. Produces a ballistic trajectory chart and table that shows the drop, velocity, kinetic energy, windage, and trajectory of a bullet.

www.shooterscalculator.com

 

[lucusloc]

Your PBR zero is 50yds where your bullet would project flat and never arc more than the 2" above the line of sight. Your max range of -2" drop is about 60yds.

Note: you can bookmark your results...

ShootersCalculator.com | Ballistic Trajectory Calculator

Calculates the ballistic trajectory of a bullet fired from a rifle, handgun or other firearm. Produces a ballistic trajectory chart and table that shows the drop, velocity, kinetic energy, windage, and trajectory of a bullet.

www.shooterscalculator.com

Yep, was just coming here to post this myself. I find it odd that the optimal zero for the laser is considerably further out than the optimal zero for the optic. My optic is 3 inches over the bore and a 25 yard zero gives a hundred yard point blank range (-3 to +1 and change back down to ~-3 again). I was not expecting to have to zero the laser out farther than the optic, but the math checks out.

I do have to say I like this BC. Lots more granular than Hornady. Is there a phone app version of it floating around somewhere?

 

[solv3nt]

Your PBR

The unofficial beer of Potland.

 

[Koda]

Yep, was just coming here to post this myself. I find it odd that the optimal zero for the laser is considerably further out than the optimal zero for the optic. My optic is 3 inches over the bore and a 25 yard zero gives a hundred yard point blank range (-3 to +1 and change back down to ~-3 again). I was not expecting to have to zero the laser out farther than the optic, but the math checks out.

I do have to say I like this BC. Lots more granular than Hornady. Is there a phone app version of it floating around somewhere?

Not surprising at all because your laser line of sight is below the barrel, the bullet will never cross the line of sight twice like sights above a barrel.

The link is a web version only, its super useful for calculating ballistics and drops. Ive used the Hornady phone app and it was ok but had issues using other peoples bullets... so I like the GeoBallistics phone app now best.

 

[lucusloc]

Not surprising at all because your laser line of sight is below the barrel, the bullet will never cross the line of sight twice like sights above a barrel.

The link is a web version only, its super useful for calculating ballistics and drops. Ive used the Hornady phone app and it was ok but had issues using other peoples bullets... so I like the GeoBallistics phone app now best.

Yeah that makes sense on closer examination. Never used a laser on a rifle platform before so never had to really think about how it all relates. My preconceived notions (laser = short range, optics = long) did not directly translate to what their zeros should be for those applications given their locations. You learn something every day.

I will check out that app. It is nice to have something at the range to validate what is being observed (especially when something seems wonky).