Labradar velocity??

[jetboat]

Sighting in my 338-06 with 225 Hornedys and 57gns H414. Expected results to be somewhere around 2500 fps +-
Screen said 5120fps! did this twice with results over 5000fps Never had it happen before.
Any ideas??

 

[JohnKielly]

Try a slower powder?

 

[Texas10]

Is it possible it's picking up your muzzle brake discharge?

 

[boltfluter]

Your Lab Radar is dyslexic! Sorry, couldn't help myself.

Paul

 

[jetboat]

No muzzle brake.
Maybe its the due to spitting on the bullets before seating
??

 

[Bob L.]

Sighting in my 338-06 with 225 Hornedys and 57gns H414. Expected results to be somewhere around 2500 fps +-
Screen said 5120fps! did this twice with results over 5000fps Never had it happen before.
Any ideas??

I have had this happen a couple of times. The radar is probably picking up unburned powder particulates in the ejecta. Try angling the unit a little more downrange (a little more parallel to the bore axis).

 

[rayporter]

unburned powder? mmmmm

my muzzle loader will register -even with sabots.

but a 20 ga slug never shows up.

 

[Bob L.]

unburned powder? mmmmm

my muzzle loader will register -even with sabots.

but a 20 ga slug never shows up.

My reply is only a theory. The powder residue, maybe including the gases from combustion, instead of just unburned powder, is the only thing I could imagine that would have a higher velocity than the projectile. When I did change the direction of the Labradar, the velocities were what I expected them to be.
Who knows what the software or firmware does, though. It could be the culprit. I never contacted Labradar to see what they said.

 

[jetboat]

I always set up the Labradar just in back from the muzzle. 2 to 3 inches.
None of my rifles have brakes except the RPR 6.5 and never had a problem with it.
My 338 wm and 300 weatherby both shake it around pretty good though but always records the shot.
Hope I don't shake the guts out of it, will try again in the morning.

 

[Ballisticboy]

I have never used LabRadar but I have used multi thousand dollar muzzle velocity doppler radars in pairs when testing rifles. We found that it was always very difficult to get the radars to agree with each other to less than a couple of feet per second (on artillery trials they have to agree to less than 1 ft/sec), the biggest difference we saw was about 130 ft/sec which is nowhere near your apparent error.
After years of experimentation with positions and directions we found the best place was as close to the barrel as possible with the radar aligned with the gun. The radar was positioned just behind the muzzle so your distance behind is about right.
It seemed that most of the difference in recorded velocities between the two radar sets was due to the curve fitting algorithms, particularly if the number of data points was low. Weather conditions could also play a part in the number of data points and the distance tracked.

 

[dcali]

It seemed that most of the difference in recorded velocities between the two radar sets was due to the curve fitting algorithms, particularly if the number of data points was low.

This seems like a plausible explanation. If the labradar was unable to capture the data points well, it may have just fit the line through some erroneous data points.

If the labradar has trouble with .22 bullets, I'm not sure I buy that it's uburned powder, which I'm guessing isn't going 5000 fps anyhow.

 

[rardoin]

I have had a handful of shots record a MV which was almost exactly double the expected velocity...like yours. The downrange velocities were in line with the other shots from the same group and I was able to extrapolate a very approximate velocity. This odd quirk occurred randomly and rarely using 6.5 and 6 mm bullets.

 

[Ned Ludd]

Regardless of the underlying cause, you know it's an error on the part of the LabRadar. Clearly you're not pushing those bullets at 5000+ fps. Because you know this, it's relatively simple to try a few things and see if the issue goes away. As mentioned, changing the aimpoint of the LabRadar unit is probably a good idea. You might also adjust the offset distance in the unit controls, or at least check that it is correct. Check your acoustic trigger setting, I find that having the unit set on "1" occasionally picks up false triggers. I would also make sure that the muzzle blast isn't excessively buffeting the unit. A few simple changes will likely make the problem disappear.

Edited to add: the LabRadar does not directly measure V0, it back-calculates it from data taken once the bullet enters the radar beam at some distance downrange. So any anomalies in data collection have the potential to create seemingly strange results because because the number that shows up on the screen (V0) is not measured directly.

 

[Jdne5b]

Ideas?

1. Make sure it's set to rifle
2. Make sure your distances chosen are shorter than the range you're shooting at. I had some very strange results when shooting at 50 yards but my last two distances were 60 and 75 yards

 

[Ned Ludd]

Ideas?

1. Make sure it's set to rifle
2. Make sure your distances chosen are shorter than the range you're shooting at. I had some very strange results when shooting at 50 yards but my last two distances were 60 and 75 yards

Jeremy, strange as in how? What did the LabRadar do to handle that? My first thought would be that it would calculate in the velocity at the last two distances (i.e. stopped in the berm = zero) LOL. But I'm guessing the that the unit can tell the projectile/beam couldn't be read out to the longest settings. Is that correct? JOOC - what is the longest "range" distance you have ever successfully used in the LabRadar settings? I have never changed mine from the factory preset, but have often thought of doing it. That would be very beneficial if it can read .30 cal projectiles consistently at 75 yd (or more) when aimed properly.

 

[Jeff A]

I always set up the Labradar just in back from the muzzle. 2 to 3 inches.
None of my rifles have brakes except the RPR 6.5 and never had a problem with it.
My 338 wm and 300 weatherby both shake it around pretty good though but always records the shot.
Hope I don't shake the guts out of it, will try again in the morning.

What did the Folks at LabRadar say? Surely you've called them by now. They do have excellent support.

 

[Jdne5b]

Jeremy, strange as in how? What did the LabRadar do to handle that? My first thought would be that it would calculate in the velocity at the last two distances (i.e. stopped in the berm = zero) LOL. But I'm guessing the that the unit can tell the projectile/beam couldn't be read out to the longest settings. Is that correct? JOOC - what is the longest "range" distance you have ever successfully used in the LabRadar settings? I have never changed mine from the factory preset, but have often thought of doing it. That would be very beneficial if it can read .30 cal projectiles consistently at 75 yd (or more) when aimed properly.

I wish I could remember. It may have been really high readings, or errors, but as you say I was expecting zeros beyond 50 and it wasnt doing that.

I either called or emailed Labradar about the issue and they said the unit would keep trying to track the projectile and return false information even though there was a target and berm at 50 yds. I cant find the email so it must have been a phone call.

So when I shoot my pistol I change the distances to under my target distance.

 

[Brians356]

My reply is only a theory. The powder residue, maybe including the gases from combustion, instead of just unburned powder, is the only thing I could imagine that would have a higher velocity than the projectile.

The likelihood of unburned kernels in the ejecta is so low as to be indistinguishable from zero. All the powder has burned in the first foot or so of barrel.
-

 

[Bob L.]

The likelihood of unburned kernels in the ejecta is so low as to be indistinguishable from zero. All the powder has burned in the first foot or so of barrel.
-

Uncle!

 

[ballisticdaddy]

I have experienced a few very odd velocities on the Labradar but believe they were picking up another bullet on a crowded range. Have never seen it happen when shooting away from others.