Labradar vs. ShotMarker for Velocity Data

[Dave M.]

Unless they changed, will they record velocity over 4000 FPS ??

you could put your Labradar at 1k and shoot over it. The e-targets are sorta close, but not probably exact either

I know a guy that set his up at 200 yards on a tripod just right of his intended target and then shot his target and it provided somewhat erratic info which I believe was the Doppler radar bouncing off of his target just 10 yards in front of his Labradar. Somewhat ballsy too if you ask me.

 

[Dave M.]

The difference you are seeing in SD and ES at the target versus muzzle are partly due to variations in BC from bullet to bullet. Read Litz no BS BC articles. Target velos on Shot market and Silver Mountain are taken from the timing difference of the two microphones on each corner. Out of square or wobbly targets on windy will affect the precision and accuracy of these at target velos. Also shots coming from an angle will be off and marked with a * on Silver Mountain targets.

All true. Shots coming from an off angle are also marked on the shot marker using the lack of blue circle (I think that is the marking).

 

[DR_2297]

Labradar will give you the BC, you don’t need any further info from an e-target.

Well bc isn’t constant over a velocity spectrum. Yes the LR can give you a short range BC out to about 100 yds. I take etarget velocities with a grain of salt though but it is useful sometimes when determining if one bullet or lot etc is better than another when fired at the same day / time / conditions on the same target

 

[Ringostar]

Here’s something that the e target velocity might help with. If you’re shooting a string and have a shot drop low. You start thinking about why. Was it a condition change, like slight head wind? You can quickly glance at the velocity on target. If it’s still comparable to others, then most likely wind. If it‘s lower, then more likely load variation. I did a test once on a silver mountain target with some leftover rounds. I had a couple that had been loaded prior with a couple thousandths shorter seating depth, and 5 current loads. Same bullets and charge weight. The 2 prior loaded rounds hit slightly higher on target, with a slightly higher on target velocity.

 

[CharlieNC]

How do you plan on using the terminal velocity? Unless you're working on BC adjustments, "truing" muzzle velocity based on drop at 1000yd works well.

 

[Pres100]

wrong info posted and removed

 

[Jeff Porter]

A lot of guys will use the drop at 600 to true the muzzle velocity ( sdjust MV inteh app until it matches real world drop value) and drop at 800-1000 to true the BC ( adjust BC in App to match drop at distance) on the ballistics calculators. dont really use the at target velo since it is typically not an easy varible to get. be curious to see if you trued up using MV and BC if the Etarget velos match up.

FWIW - I have used e target velos at 100 yards in JBM program and shot cold bore X at 800 with the dope form that... somedays I'd rather be lucky than good.

 

[davidjoe]

I have wondered how the ShotMarker microphones and plotting function could be considered accurate for purposes of determining shot location, but not very accurate for determining velocity.

Looking at the two directional sensors on each microphone, my understanding is that they would define the corners two flat “planes” out in front of the target, one behind the other. They would “fire” at the peak of pressure in both planes, and extrapolate the position of the bullet from mic firing differentials.

They determine the X and Y angle of entry by comparing the change in position up-down and left-right of the two screens. This is presented on what is usually an admin-only screen.

The inherent precision required to ascertain a reliable “plotting” of the target impact is orders of magnitude higher than the difficultly of determining simply “when” each of two “planes” or virtual “screens” a known distance apart, is pierced, from peak pressure level.

The velocity function in other words, if unreliable, would seem to me to necessitate that all of the system’s functions are unreliable. I would tend to think that the ShotMarker system is actually overkill for a sound-based chronograph.

 

[LVLAaron]

I have wondered how the ShotMarker microphones and plotting function could be considered accurate for purposes of determining shot location, but not very accurate for determining velocity.

Looking at the two directional sensors on each microphone, my understanding is that they would define the corners two flat “planes” out in front of the target, one behind the other. They would “fire” at the peak of pressure in both planes, and extrapolate the position of the bullet from mic firing differentials.

They determine the X and Y angle of entry by comparing the change in position up-down and left-right of the two screens. This is presented on what is usually an admin-only screen.

The inherent precision required to ascertain a reliable “plotting” of the target impact is orders of magnitude higher than the difficultly of determining simply “when” each of two “planes” or virtual “screens” a known distance apart, is pierced, from peak pressure level.

The velocity function in other words, if unreliable, would seem to me to necessitate that all of the system’s functions are unreliable. I would tend to think that the ShotMarker system is actually overkill for a sound-based chronograph.

Next time I'm out I'll compare the data from my LR and Shotmarker. I'll be shooting at 200 tomorrow. I'll compare ES/SD/Velocity from the two.

If you aren't testin' you're guessin'

 

[Tarmacshooter]

I have wondered how the ShotMarker microphones and plotting function could be considered accurate for purposes of determining shot location, but not very accurate for determining velocity.

Looking at the two directional sensors on each microphone, my understanding is that they would define the corners two flat “planes” out in front of the target, one behind the other. They would “fire” at the peak of pressure in both planes, and extrapolate the position of the bullet from mic firing differentials.

They determine the X and Y angle of entry by comparing the change in position up-down and left-right of the two screens. This is presented on what is usually an admin-only screen.

The inherent precision required to ascertain a reliable “plotting” of the target impact is orders of magnitude higher than the difficultly of determining simply “when” each of two “planes” or virtual “screens” a known distance apart, is pierced, from peak pressure level.

The velocity function in other words, if unreliable, would seem to me to necessitate that all of the system’s functions are unreliable. I would tend to think that the ShotMarker system is actually overkill for a sound-based chronograph.

Adam has a sound based chronograph. It uses transonic crack but is used on the vertical plane. I’d assume the shot markers are using 8 mics in the 3D plane. X Y and Z.
as have been mentioned the speed at target is considered to be fairly inaccurate.

 

[davidjoe]

One of the reasons I have considered target velocity to be accurate is that Target V (TV) matches up so well with the BC and MV components. Any two of those three, assuming they are correct, will determine what the third value should be. Like calculating the third leg of a triangle, accuracy here is either self-proving for all three, or proof of an error with at least one variable, if gapped.

When these were newly introduced I was impressed how well the higher or lower velocity of shots correlated with high and low impacts, as well as lower velocities drifting downwind, and I wasn’t a proponent of a switch to them.

Like probably most of us at one time or another, I have sometimes felt like the SD figure at the target, on display for all to see, is publicly mocking my reloading, but it always, without fail, is an exceptionally low number for both the very best TR and Open guns/shooters, no matter what the location, distance, or target they are on.

When we shift targets in the same day to pair fire, the low SD (or high one) follows the gun. As this is just what we would expect of the top guns, and as SD is derived purely from TV’s, that does create a very strong implication that TV is being accurately reported. It also implies that the ShotMarker consistently, without much aberration, correctly reports TV, because SD could never be small, if inaccurate smatterings of error were present through the string. While it’s theoretically possible that errors compressing results could improve SD, they wouldn’t do so in a way to always favor the smallest shooting guns.

There is no explanation for why the lowest SD’s follow the smallest shooting guns around the country, that is compatible with ShotMarkers not reporting TV accurately. Again, this isn’t easy to say from one that was 100% happy with pulled targets.

 

[INTJ]

One of the reasons I have considered target velocity to be accurate is that Target V (TV) matches up so well with the BC and MV components. Any two of those three, assuming they are correct, will determine what the third value should be. Like calculating the third leg of a triangle, accuracy here is either self-proving for all three, or proof of an error with at least one variable, if gapped.

When these were newly introduced I was impressed how well the higher or lower velocity of shots correlated with high and low impacts, as well as lower velocities drifting downwind, and I wasn’t a proponent of a switch to them.

Like probably most of us at one time or another, I have sometimes felt like the SD figure at the target, on display for all to see, is publicly mocking my reloading, but it always, without fail, is an exceptionally low number for both the very best TR and Open guns/shooters, no matter what the location, distance, or target they are on.

When we shift targets in the same day to pair fire, the low SD (or high one) follows the gun. As this is just what we would expect of the top guns, and as SD is derived purely from TV’s, that does create a very strong implication that TV is being accurately reported. It also implies that the ShotMarker consistently, without much aberration, correctly reports TV, because SD could never be small, if inaccurate smatterings of error were present through the string. While it’s theoretically possible that errors compressing results could improve SD, they wouldn’t do so in a way to always favor the smallest shooting guns.

There is no explanation for why the lowest SD’s follow the smallest shooting guns around the country, that is compatible with ShotMarkers not reporting TV accurately. Again, this isn’t easy to say from one that was 100% happy with pulled targets.

The guns that shoot the smallest don't worry too much about ES and SD and haven't made much effort to adopt e-targets. Now I would love to see e-targets used for the slighter period, and then have the paper targets come up for record. (E-targets still aren't accurate enough for LR BR record targets.......yet).

We are constantly tuning our rifles, and we often DON'T find a correlation between lowest ES/SD and smallest group. We also frequently see where higher powder charges print a little lower than lower powder charges. We in fact look for that overlap when picking a tune.

All that said, the above observations are based on MV, not TV. Makes me want to buy a shot marker for my own tuning sessions. There are lots of questions that perhaps could be answered.

Like why does the low node usually shoot better at 600 and under, but the high node shoots better at 1000? I have always just assumed that that very small amount of less flight time of the high node offsets what may be a slightly more precision load. But maybe something else is going on there.......

 

[CA_Shooter]

I've found on very windy days, where targets are rocking back and forth, everyone's SDs are 25+

And to @davidjoe question above...are those shots reliable?

 

[davidjoe]

I've found on very windy days, where targets are rocking back and forth, everyone's SDs are 25+

And to @davidjoe question above...are those shots reliable?

I would say that SD’s reported at the target are going to be less reliable when there are major wind changes perpendicular with the target (head and tail wind changes that rock the target). But that’s also the source of actual, not just reported, variance in velocity, as the bullet V is affected by it.

By and large I think those high SD’s are real in variable perpendicular wind at LR, just like horizontal dispersion increases in variable crosswind. I think the target itself serves as a wind block that places the microphones in a “shadow” that we don’t get on wind parallel to the target.

For wind coming from directly behind the target, wind at the microphones has been blocked, and for wind coming straight at the target, it’s similar to the benefit of a large building right behind you slowing down a headwind before it gets to you. At the mics, that wind has already slowed moving forward and started to be forced sideways from wind at the middle of the target going around it. If the e-target didn’t “luck” into this situation, I think it would be just as succeptibke to perpendicular Doppler effect.

 

[rhovee]

I don’t put much faith in the E-target SD/ES. I’ll be shooting 180 Hybirds, 230 Hybrids etc at 600 along side my LabRadar at my side. ES will be 12. And at the target ES will be 21. Even with a 1 percent BC difference, you wouldn’t have that large of margin at 600