LabRadar Accuracy With Small Bullets?

[flyingbrass]

A friend bought a LabRadar some time ago, which we have used to work up loads. We have been shooting .223. He is using Sierra 77 TMK bullets, and I've been using Hornady 73 ELD.

I had a load that initially showed a reasonably tight ES, SD and average velocity over multiple loading and shooting sessions. Then, somewhere along the line, as we experimented and changed chronograph positions, my average velocities began shifting considerably from session to session. ES and SD opened up some from before, but not much.

Is this due to the chronograph? I've read that LabRadars are not well-suited to picking up small projectiles. We ran the chrono at its low power setting, which is the only setting it would report velocities in our conditions. We were shooting prone and eventually ended up with the chrono positioned above our barrels.

My question is how does the LabRadar tend to fail on small bullets? Will it simply not report a velocity, or will it report incorrect velocities? Any experience with this?

My friend gets consistent results from the LabRadar using the 77 grain TMK bullets with a larger base. My 73 ELD bullets have a relatively tiny base in the scheme of .223 bullets, and I'm getting far more reported velocity variation between sessions than I'd expect. Here is a picture of some bullet bases for comparison.

Left to right:

Hornady 73 ELD
Hornady 75 BTHP
Sierra 77 TMK
Hornady 55 FMJ
Hornady 55 SP (flat base)

 

[flyingbrass]

I'm thinking that perhaps the smaller base bullets aren't being tracked as far out by the LabRadar as the larger base bullets. This could make the approach angle into the cone of detection more of a factor in calculating the muzzle velocity. In other words, position of the muzzle in relation to the chrono may be causing the reported differences. We're talking 40ish FPS or even more difference at times in average velocity between sessions when ES is usually not over 30 and SD 10ish. It's the average that changes, not the spread. 8208 XBR powder, which is fairly temp stable, and only minor temperature differences between shooting sessions at the same location.

Thoughts?

 

[flyingbrass]

While these are different batches of loads shot under different environmental conditions on different days, I've recently fired two 5 shot groups at 700 yards. The first was with some varying wind. I dialed 17.75 MOA. The vertical spread was 5.8" with the group center 2.6" high.

Last time, two days ago, I dialed 17.5 MOA, which put me dead on for elevation. I made several hits on a palm size target when I got the wind hold correct. 5 shot group size shot at paper was 4.98" with the center of the group about .75" below target center (best clustered 3 averaged .18" high). This mostly matches up with my previous group (give or take a little for wind), and doesn't indicate a wide velocity variation, certainly not of the magnitude that the chrono was telling me.

 

[piie]

Have a look at the raw CSV's on the flash card - there are much more distance velocity readings in the files than what is displayed on the unit while shooting. If the unit is battling to detect or measure velocity at or from a specific distance, it will show in the file.

 

[Ballisticboy]

Radars do not measure muzzle velocity, they measure the velocity of the bullet relative to the radar down range and then try to interpolate the data back to the radar to arrive at a start figure. The further the bullet is away from the radar before usable data is obtained the more difficult it is to interpolate back to an accurate start figure. The gun should therefore be as close to the radar as possible to try to obtain the maximum data possible to help the interpolation. Putting the radar close to the gun also means the velocities the radar is measuring are closer to the velocities of the bullet relative to the gun.
The shape and size of the bullet base will have some effect on the amount of data the radar obtains. Again the more data the radar gets the better the interpolation will be.
The radar can only measure time and relative velocity so any other data in the csv file cannot be raw data but will have to have been derived in some way.

 

[kvd]

The labRadar will track 22LR bullets with no difficulty - but one must adjust the menu settings. It will track .177 caliber pellets as well but I've never tried those.

 

[Dusty Stevens]

If mine has an issue, like with very small bullets, it stops tracking like at 75yds. Cant figure this one out

 

[Shinbone]

I have a similar question about the velocities reported by my Labradar, but with .264" bullets.

When trying a new powder, I'll first do a "rough" powder test by shooting 2-shot groups, starting at a low powder charge and working up until I see pressure signs. This allows me to sweep through a wide range of loads and find max pressure relatively quickly. (I do these large sweeps because there is very little load data for the .264 Win Mag with modern powders, especially with 120gn bullets). Then, I'll do a "fine" powder test by shooting 5-shot groups around whatever load that showed good accuracy potential in the rough powder test.

While I have done the rough powder test with multiple powders, I have only followed up with a 5-shot fine powder test with two powders - Vihtvouri N570 and Reloader 33. In both cases, there was a substantial velocity difference (100fps - 150 fps) between the rough test and the fine test. The velocity discrepancy was 4% for the N570 and 5% for the RL 33, which is substantially outside Labradar's stated 0.1% accuracy claim. With both powders, the rifle still appeared to be shooting in its accuracy node, leading me to believe that the rifle was shooting at the same velocity and that the Labradar was reporting incorrect velocities. But, I am still not sure what actually happened, there. And, I don't know which set of numbers are correct, if any.

Maybe I had the instrument set wrong at some point in this load development? But, it is my understanding that the settings are more for reliable triggering and calculating a "power factor" than for basic velocity accuracy.





I have had a couple of long discussions with the folks at Labradar about what might be happening to cause this apparent velocity discrepancy. The Labradar technicians are nice people and very willing to talk, but they are also adamant that the instrument does not and can not produce accuracy errors. Their position is the instrument is either pretty much dead-on, or it produces a nonsensical result that is easy to identify as an erroneous number. I've read reports on a side-by-side comparison between the Labradar and a "professional" ballistic radar system, where the two instruments agree very closely. However, I believe I am getting erroneous velocity numbers, somewhere, somehow.

My Labradar unit first "sees" my .264 bullets at about 6 meters from the muzzle. Meaning, the muzzle velocity is a calculated, not a directly measured, number. I can only conclude that, while any single data point in the set of measurements made for a single shot is indeed accurate, the error arises when instrument extrapolates the data to estimate muzzle velocity. In other words, there is a problem with the computation side of the process with my unit.

Looking at the complete data set on the memory card for each shot, all the files look good to my layman's eye. I've tried changing position of the Labradar unit relative to my gun, I've tried aiming the unit better so it tracks the bullet to a longer distance, and I've also tried triggering the gun with an external accelerometer trigger, all with no noticeable change in velocity numbers.

I suppose the next step is to set up another chronograph in addition to the Labradar, and compare results of the two instruments to try to figure out what is going on.

 

[piie]

I have a similar question about the velocities reported by my Labradar, but with .264" bullets.

When trying a new powder, I'll first do a "rough" powder test by shooting 2-shot groups, starting at a low powder charge and working up until I see pressure signs. This allows me to sweep through a wide range of loads and find max pressure relatively quickly. (I do these large sweeps because there is very little load data for the .264 Win Mag with modern powders, especially with 120gn bullets). Then, I'll do a "fine" powder test by shooting 5-shot groups around whatever load that showed good accuracy potential in the rough powder test.

While I have done the rough powder test with multiple powders, I have only followed up with a 5-shot fine powder test with two powders - Vihtvouri N570 and Reloader 33. In both cases, there was a substantial velocity difference (100fps - 150 fps) between the rough test and the fine test. With the N570, the rifle still appeared to be shooting in its accuracy node, leading me to believe that the rifle was shooting at the same velocity and that the Labradar was reporting incorrect velocities. But, I am still not sure what actually happened, there. And, I don't know which set of numbers are correct, if any.





I have had a couple of long discussions with the folks at Labradar about what might be happening to cause this apparent velocity discrepancy. The Labradar technicians are nice people and very willing to talk, but they are also adamant that the instrument does not and can not produce accuracy errors. Their position is the instrument is either pretty much dead-on, or it produces a nonsensical result that is easy to identify as an erroneous number. I've read reports on a side-by-side comparison between the Labradar and a "professional" ballistic radar system, where the two instruments agree very closely. However, I believe there is little doubt that I am getting erroneous velocity numbers, somehow.

My Labradar unit first "sees" my .264 bullets at about 6 meters from the muzzle. Meaning, the muzzle velocity is a calculated, not a directly measured, number. I can only conclude that, while any single data point in the set of measurements made for a single shot is indeed accurate, the error arises when machine interpolates the data to estimate muzzle velocity. In other words, there is a problem with the computation side of the process with my unit.

Looking at the complete data set on the memory card for each shot, all the files look good to my layman's eye. I've tried changing position of the Labradar unit relative to my gun, I've tried aiming the unit better so it tracks the bullet to a longer distance, and I've also tried triggering the gun with an external accelerometer trigger, all with no noticeable change in velocity numbers.

I suppose the next step is to set up another chronograph in addition to the Labradar, and compare results of the two instruments to try to figure out what is going on.

Should be fairly easy to use excel functions to extrapolate and compare what its zero v is versus what the lab says if you are worried that your unit is somehow extrapolating incorrectly?

 

[Ballisticboy]

Testing against "professional" ballistic radars is no guarantee of accuracy. All the muzzle velocity radars we were using were professional kit costing 12000-30000 dollars. Using them in pairs I have seen two radars agreeing to less than 1m/s having a gap of 14m/s five shots later with no one touching them or interferring with them. This was on a 9mm bullet with a velocity of around 300m/s so a relatively large discrepancy. A single system, which we were using in an early test on a small calibre projectile that we had no muzzle velocity data on, was later shown to have been 10% in error. During analysis of the results it was obvious there was a problem as the projectile needed a negative drag to reach its impact point.
Most users, even some of the manufacturers, don't know of these problems as they do not regularly use more than one system at a time. We only used multiple systems due to our background in artillery range and accuracy trial methods which we transferred to small arms testing.

 

[Shinbone]

The OP seems to asking about a velocity shift and noise in the data.

The velocity errors I am seeing in the two posted data sets appear to be a velocity shift that exceeds any "noise" in the data.

 

[flyingbrass]

Ballisticboy, it's interesting that even expensive radars can show such swings. So far, the LabRadar seems to read consistently for me within a shooting session. My average velocities vary considerably between sessions, even when I've used the same batch of ammo under almost identical conditions.

We plan to chrono loads again soon at a different location. We'll shoot off a bench instead of prone, which hopefully will allow using the higher Tx power. Maybe if my bullets can be tracked for a longer distance the results will be more consistent over time.

During my head scratching over reported velocity differences I wondered if the moisture content in my powder had been changing. My powder is stored inside in an air conditioned environment, but the jug was new. I charge by weight, but to track any density changes I throw 10 charges with an RCBS Uniflow. After weighing, I throw 10 more and weigh again. 8208 XBR meters very well. The measure stays at the same setting, so I can compare over time.

Weight of 10 thrown charges

8208 XBR - original 1 lb. can
------------------------------------
5/6/19 222.0 (same both times)


8208 XBR from 8 lb. jug
------------------------------------
5/6/19 223.4 (same both times)
5/10/19 223.4 (same both times)
7/10/19 224.4 (same both times)
8/30/19 224.6 (224.5, 224.7, 224.6)

BTW, when freshly opened the new lot of powder needed about 22.8 grains to match the velocity of the older powder at 22.6 grains. This pretty much matches the density difference. Makes me wonder if a good portion of the lot to lot variation in powder is due to differences in moisture content.

My powder has gained a slight amount of weight over time (a little over a tenth of a grain per typical charge), but this doesn't match or explain the large session to session swings reported by the LabRadar. I'm not mixing lots. Ive been using only powder from the 8 lb. jug for load development and testing.

While not related to my question, others may be interested in this comparison. Several months ago I used 2 chronographs. Strings were 4 rounds each. The LabRadar was at the muzzle, and my ProChrono was 16' in front. The 16' distance should read about 10 FPS slower than muzzle velocity. In the chart I've added 10 FPS to the ProChrono averages.

As usual, I did my best to level the ProChrono with the rifle so I was shooting as straight through it as possible, but some of the difference could be from minor misalignment. If the chrono is tilted the bullet will travel farther between sensors, which will show a slower velocity than actual.



The LabRadar showed lower extreme spreads. It seems to be more precise, but I don't trust its accuracy.

 

[dellet]

You might try marking where you rifle/rest is setup and also where the Lab Radar is set. That simple thing helped my day to day variations a noticeable amount.

 

[Shinbone]

You might try marking where you rifle/rest is setup and also where the Lab Radar is set. That simple thing helped my day to day variations a noticeable amount.

dellet - interesting suggestion. How much of a difference in velocity measurements did ensuring the rifle/rest/Labradar were in exactly same place each time make?

 

[dellet]

dellet - interesting suggestion. How much of a difference in velocity measurements did ensuring the rifle/rest/Labradar were in exactly same place each time make?

I don't know if could give an actual number off the top of my head, but enough to notice.

When I first got the radar unit I used it with the standard chronograph. first thing noticed was the closer to the barrel I placed the unit, the closer the reading at 5 yards matched the chronograph.

The next thing I noticed was after a few shots or breaking down and setting up again the Lab Radar readings again would be out of synch with the chronograph. Only thing moved was the rifle and Lab Radar, if the rifle was in the same place in the non-moved rest and chronograph, had to be radar placement.

Last clue was after marking my shooting table at home which is not exactly up to benchrest standards. Numbers would get screwy, then maybe a missed shot. Check the radar base and it was clear it had walked.

By using the chronograph in tandem with the Lab Radar, I think I cut my learning curve down considerably. I think a lot of things I might have blame on the Radar unit were easier to see as operator error.

The more exacting and repeatable the setup, the more repeatable the results. Or simply put, Garbage in, Garbage out.

 

[bulwaagh]

I'm thinking that perhaps the smaller base bullets aren't being tracked as far out by the LabRadar as the larger base bullets.

This has been my direct experience. Boattail 22cal bullets are trickier than my 22LR bullets to track. Its not bad, but I consistently get 100yd readings and higher S/N ratios than with my .223 Rem.

This could make the approach angle into the cone of detection more of a factor in calculating the muzzle velocity. In other words, position of the muzzle in relation to the chrono may be causing the reported differences. We're talking 40ish FPS or even more difference at times in average velocity between sessions when ES is usually not over 30 and SD 10ish. It's the average that changes, not the spread. 8208 XBR powder, which is fairly temp stable, and only minor temperature differences between shooting sessions at the same location.

Thoughts?

I adopted a 3D printed picatinny adapter for my labradar and attached the 2nd cheapest red-dot sight that amazon had. After zero'ing my labradar, my .223 rounds are much more reliable and S/N numbers are greater.

 

[Shinbone]

bulwaagh - sounds interesting. I’d love to see a photo of your set up, especially the picatinny adapter.

 

[Mad_Charlie]

Maybe something like this, only the bracket is plastic.

 

[Mad_Charlie]

Fellow over on Snipers Hide selling the 3D printed setup.

 

[longtrapshootn]

I run my 223 with the Radar and have no issues picking it up. I have ran the radar and magneto at the same time and usually have around a 1-2 fps difference.