parallel or converging on your laser setup?

HighValleyRanch · August 16, 2018, 01:04 PM

This is an excellent video on the theories of sighting in your laser.
The guy is a very excellent shooter!
https://www.youtube.com/watch?v=TUrcrd44HJk

Parallel, in which the laser is a parallel line to the bore axis; or converging, in which you set a distance as which the laser will be the same impact point as the bore line.

Since parallel difference remains the same, no matter what the difference, the impact will always only be 2.5 inches higher than the dot(or whatever the distance is from your bore to laser center) no matter the distance.

Converging will give you high shot closer than what you set it for, and lower shots for any distance further.

So how do you have your particular laser setup?

Onward Allusion · August 16, 2018, 01:56 PM

I sight my lasers at 10 yards. So, I guess I'd be hitting low beyond that distance. For me a laser is just an aid for point shooting at fairly close distances. Beyond 10 yards, I'd either run the other way or use sights.

OhioGuy · August 16, 2018, 04:49 PM

Converging at 15 yards -- on my Walther PPS it's about 2 inches below the bore axis. So I'll be +/- 2 inches vertically anywhere from 0 - 30 yards, which is close enough for my purposes

If the target is a 3x5 index card oriented vertically, and I am at the center, then (in theory) I will still land a hit somewhere on the card anywhere out to 30 yards.

(Seriously doubt I'd even see that dot from so far away).

The parallel theory is interesting -- keeps things constant -- no matter where the target is, make sure to aim 2" below your intended POI and you'll get consistent results.

Rangerrich99 · August 16, 2018, 05:42 PM

Mine (I have four) are set to 15 yds (45 ft.). Three are CTC grip panel lasers (down the slide), so the convergence is lateral not vertical. However, out to 25 yds there's not enough of an error to worry me (an inch or so?), at least for defensive purposes.

**44 AMP** · August 17, 2018, 10:17 AM

Quote:

Since parallel difference remains the same, no matter what the difference, the impact will always only be 2.5 inches higher than the dot(or whatever the distance is from your bore to laser center) no matter the distance.

No, it won't.
Or rather, yes, a line from the center of the bore, and the line of the laser will always be X apart when set parallel, no matter the distance.

BUT, the BULLET WILL NOT!!!

Bullets do not travel in a flat straight line, they travel in a arc, due to gravity. Gravity works on the bullet from the moment it leaves the muzzle, and it begins "falling". We compensate for this with our sights.

Compared to the line of sight, (which is a straight line, like the laser) the bullet leaves the muzzle at an upward angle. It "rises", crosses the line of sight, arcs above it for a time, then falls down through the line of sight. The point where it crosses the line of sight the second time is usually our "sighted in" range.

If your laser is mounted parallel to the bore, and above the bore, the bullet will cross it, twice, at different distances, one close, the other far.

If your laser is below the bore, the bullet will only cross it once, and at a distance. Mounted parallel and to either side of the bore, the bullet will NEVER cross the laser's path.

You can only alter the bullet's arc by changing its velocity, which change the distance from the muzzle where the bullet crosses the laser's path. (line of sight)

If you want the paths to intersect at any other distance, then the line of sight/laser must converge with the line of the bore, not be parallel.

Hope this helps.

HighValleyRanch · August 17, 2018, 11:51 AM

Excellent point 44amp!
I looked it up on Chuck hawks chart and a 147 grain 9mm would drop about 2" at 25 yards.
So if it was set up exactly parallel, with no arc about the sighting line, then it would be 4.5 inches low at 25 yards with a parallel setup.

The only reason a bullet arcs above the line is sight is because the sights are setup for that.
If the gun were perfectly parallel to the ground, the bullet would travel straight and start to fall as it gains distance. It would not come out in an arc naturally, although I imagine that the recoil and time in the barrel would have some effect on that as well.

**44 AMP** · August 17, 2018, 04:32 PM

Gravity acts on a bullet from the instant it leaves the barrel. And the pull is constant, Galileo proved it centuries ago. Acceleration due to gravity is a constant, and is the same regardless of the object's weight.

( in atmosphere, surface area/air resistance plays a part in determining the terminal velocity of a falling object, but when talking short distances, it can be disregarded)

Bullet drop is a constant, it's acceleration due to gravity. How much a bullet drops below the line of sight is a factor of how long the bullet is in flight.

Quote:

The only reason a bullet arcs above the line is sight is because the sights are setup for that.
If the gun were perfectly parallel to the ground, the bullet would travel straight and start to fall as it gains distance. It would not come out in an arc naturally, although I imagine that the recoil and time in the barrel would have some effect on that as well.

Its not just "the sights are set up for that" its "the GUN is set up for that". you can look at it either way, but either the line of sight is angled "down" in relation to the line of the bore, or the bore is angled "up" in relation to the line of sight. The point is that #1) because of gravity, the bullet always travels in an arc (down and forward), so long ago gunmakers discovered that the line of sight, and the line of the bore MUST converge or else your sights are useless. And that because of the angle of convergence of the two, and the arc of bullet flight, the bullet will cross the line of sight twice, once close to the muzzle, and then later, at a greater distance.

This is what allows us to sight in our firearms.

Recoil and time in the barrel play a role in where the muzzle is, when the bullet exits. They do not have any effect on the flight profile of the bullet only where it begins.

marine6680 · August 19, 2018, 03:58 PM

Yes, bullet drop is a thing.

The fixed sights on a pistol are setup in a way as to work with the geometry of the barrel in the slide, to give a zero point determined by the manufacturer.

A pistol that is made with bullseye target shooting in mind might be setup with a zero point of 25yds, and one designed for combat and defense might be zeroed for 15yds.

For bullet drop, gravity affect the bullet as soon as it leaves the barrel. If the barrel is perfectly parallel to the ground, that means the bullet will begin to fall below the plane of the barrel immediately... Bullets travel fast, and the pull of gravity being an acceleration, means that for the first several yards, the amount the bullet falls before reaching a target at that distance would be barely noticeable. Likely the inherent accuracy spread would hide it. Point being... It will be an arc, with the apex of the arc being the point where it leaves the barrel. From then on, it will be an arc that is falling towards the ground.

Sights on a firearm are not setup to be parallel with the barrel... Because the barrel sits below the sights, in order for the line of sight through the sights to intersect with the flight path of the bullet... Either the sights must be set up in a way that makes the barrel/firearm point slightly upwards, or the barrel itself must sit in the firearm with an upwards angle. Usually it will be the former setup.

This causes the bullet path to be a more traditional looking arc, where the bullet will rise to an apex, then fall again. Due to the nature of gravity accelerating the downward fall, and the fact that the bullet is losing speed, which allows more time for gravity to affect it, the arc of the bullet will exaggerate and get steeper with time/distance.

So... When it comes to laser sights, parallel to bore or a set converged point... It doesn't matter. The bullet path will converge on the path of the laser at some point in it's travel.

With a converged path, at least you determine that convergence point.

I suggest 10yds as being a good point to zero a laser. Your bullet impact should be withing a couple inches of that point from contact distance, out to 20yds or so... But you should always check this for yourself and your firearm.

raimius · August 19, 2018, 11:10 PM

Parallel to the bore would result in all impacts being below the laser (unless the laser starts under the bore, then it would converge at a set distance for that ammo).

Set your laser to a practical distance. Zeroing a laser for 100yds does nothing if you can't see it at 100yds!
I find 10-15 works decently for me. I use the laser for speed and awkward position shooting. It probably won't be point of aim/point of impact, but it will be close enough to get hits on reasonable sized targets.

View Poll Results: laser setup: parallel or converging
parallel	3	23.08%
converging	10	76.92%
Voters: 13. You may not vote on this poll

August 16, 2018, 01:56 PM	#2
Onward Allusion Senior Member Join Date: November 17, 2009 Location: Back in a Non-Free State Posts: 3,133	I sight my lasers at 10 yards. So, I guess I'd be hitting low beyond that distance. For me a laser is just an aid for point shooting at fairly close distances. Beyond 10 yards, I'd either run the other way or use sights. __________________ Simple as ABC . . . Always Be Carrying

August 16, 2018, 04:49 PM	#3
OhioGuy Senior Member Join Date: August 11, 2016 Posts: 1,089	Converging at 15 yards -- on my Walther PPS it's about 2 inches below the bore axis. So I'll be +/- 2 inches vertically anywhere from 0 - 30 yards, which is close enough for my purposes If the target is a 3x5 index card oriented vertically, and I am at the center, then (in theory) I will still land a hit somewhere on the card anywhere out to 30 yards. (Seriously doubt I'd even see that dot from so far away). The parallel theory is interesting -- keeps things constant -- no matter where the target is, make sure to aim 2" below your intended POI and you'll get consistent results. Last edited by OhioGuy; August 16, 2018 at 04:57 PM.

August 17, 2018, 11:51 AM	#6
HighValleyRanch Senior Member Join Date: July 15, 2005 Posts: 4,066	Excellent point 44amp! I looked it up on Chuck hawks chart and a 147 grain 9mm would drop about 2" at 25 yards. So if it was set up exactly parallel, with no arc about the sighting line, then it would be 4.5 inches low at 25 yards with a parallel setup. The only reason a bullet arcs above the line is sight is because the sights are setup for that. If the gun were perfectly parallel to the ground, the bullet would travel straight and start to fall as it gains distance. It would not come out in an arc naturally, although I imagine that the recoil and time in the barrel would have some effect on that as well. __________________ From the sweet grass to the slaughter house; From birth until death; We travel between these two eternities........from 'Broken Trail"

August 16, 2018, 01:04 PM	#1
HighValleyRanch Senior Member Join Date: July 15, 2005 Posts: 4,066	parallel or converging on your laser setup? This is an excellent video on the theories of sighting in your laser. The guy is a very excellent shooter! https://www.youtube.com/watch?v=TUrcrd44HJk Parallel, in which the laser is a parallel line to the bore axis; or converging, in which you set a distance as which the laser will be the same impact point as the bore line. Since parallel difference remains the same, no matter what the difference, the impact will always only be 2.5 inches higher than the dot(or whatever the distance is from your bore to laser center) no matter the distance. Converging will give you high shot closer than what you set it for, and lower shots for any distance further. So how do you have your particular laser setup? __________________ From the sweet grass to the slaughter house; From birth until death; We travel between these two eternities........from 'Broken Trail"

August 16, 2018, 05:42 PM	#4
Rangerrich99 Senior Member Join Date: March 20, 2014 Location: Kinda near Phoenix, AZ Posts: 1,254	Mine (I have four) are set to 15 yds (45 ft.). Three are CTC grip panel lasers (down the slide), so the convergence is lateral not vertical. However, out to 25 yds there's not enough of an error to worry me (an inch or so?), at least for defensive purposes.

August 19, 2018, 03:58 PM	#8
marine6680 Senior Member Join Date: July 24, 2012 Location: Parker, CO Posts: 4,594	Yes, bullet drop is a thing. The fixed sights on a pistol are setup in a way as to work with the geometry of the barrel in the slide, to give a zero point determined by the manufacturer. A pistol that is made with bullseye target shooting in mind might be setup with a zero point of 25yds, and one designed for combat and defense might be zeroed for 15yds. For bullet drop, gravity affect the bullet as soon as it leaves the barrel. If the barrel is perfectly parallel to the ground, that means the bullet will begin to fall below the plane of the barrel immediately... Bullets travel fast, and the pull of gravity being an acceleration, means that for the first several yards, the amount the bullet falls before reaching a target at that distance would be barely noticeable. Likely the inherent accuracy spread would hide it. Point being... It will be an arc, with the apex of the arc being the point where it leaves the barrel. From then on, it will be an arc that is falling towards the ground. Sights on a firearm are not setup to be parallel with the barrel... Because the barrel sits below the sights, in order for the line of sight through the sights to intersect with the flight path of the bullet... Either the sights must be set up in a way that makes the barrel/firearm point slightly upwards, or the barrel itself must sit in the firearm with an upwards angle. Usually it will be the former setup. This causes the bullet path to be a more traditional looking arc, where the bullet will rise to an apex, then fall again. Due to the nature of gravity accelerating the downward fall, and the fact that the bullet is losing speed, which allows more time for gravity to affect it, the arc of the bullet will exaggerate and get steeper with time/distance. So... When it comes to laser sights, parallel to bore or a set converged point... It doesn't matter. The bullet path will converge on the path of the laser at some point in it's travel. With a converged path, at least you determine that convergence point. I suggest 10yds as being a good point to zero a laser. Your bullet impact should be withing a couple inches of that point from contact distance, out to 20yds or so... But you should always check this for yourself and your firearm.

August 19, 2018, 11:10 PM	#9
raimius Senior Member Join Date: January 27, 2008 Posts: 2,199	Parallel to the bore would result in all impacts being below the laser (unless the laser starts under the bore, then it would converge at a set distance for that ammo). Set your laser to a practical distance. Zeroing a laser for 100yds does nothing if you can't see it at 100yds! I find 10-15 works decently for me. I use the laser for speed and awkward position shooting. It probably won't be point of aim/point of impact, but it will be close enough to get hits on reasonable sized targets.