Accuracy of LabRadar downrange velocities?

[cal30_sniper]

Has anyone spent much time playing with the downrange velocity function of the LabRadar? I've embarked on a project recently to try and characterize some BCs for .358 and .366 caliber copper monos that I want to do some hunting with (target is to maintain 2200fps out to 500yds with a .358 or larger diameter copper mono). Last weekend I got some good data from my .358 Norma Mag, but I wanted to see if anyone else has used a LabRadar to successfully measure BCs? Some of the values are low, but measuring against a known good bullet seems to provide reasonable results.

Next trip or two I hope to gather data on the .358 200gr TTSX, .358 215gr and 255gr HHT, .366 250gr TTSX, and .366 242gr HHT. Right now I'm in a toss-up on having a Tikka barrel spun up in .358 Norma Mag, 9.3 RSM (9.3-300WSM) or 9.3-33 Nosler. Hoping this testing will help me decide, at least between the .358 and 9.3mm bore diameter.

• Hammer Hunter 196gr HHT (listed "estimated" G1 BC of .435)
  • My data shows a G1 BC of .322 when run through the Hornady Ballistics App and compared to the 25, 50, 75, and 100yd velocity. This is 74% of the advertised "estimated" G1 BC
• Hammer Hunter 215gr HHT (listed as "estimated" G1 BC of .454)
  • My data (data point of one) shows a G1 BC of .343. This is also 74% of the advertised "estimated" BC.
• Cutting Edge 275gr Maximus (no listed G1 BC)
  • My data shows a .372 G1 BC. I would have expected more from this big long bullet, especially based on the similar 250gr .338 caliber bullet which lists a .607 G1 BC. (yes, I know, a copper mono will have less BC than a comparable lead core bullet, BUT it should be close to the listed BC for a similar caliber heavy-for-caliber bullet of the same design from the same manufacturer)
• Hornady 108gr ELDM (listed .536 BC) - Using this bullet as a check-value as its BC is well verified by Applied Ballistics and my own drop measurements
  • My data from the LabRadar shows a .495 G1 BC (92% of the advertised value). I got data points at 25, 50, and 75 yds for this bullet, but it seems to be unable to pick up the smaller bullet at 100yds.

196gr HHT Data:

275gr Maximus Data:


108 ELDM Data:

 

[hereinaz]

This the new small form factor LR?

 

[cal30_sniper]

This the new small form factor LR?

30 rounds of it felt very large form factor on my shoulder

 

[hereinaz]

30 rounds of it felt very large form factor on my shoulder

View attachment 873426

Hahahaha, definitely not small form factor in the rifle!

I was talking about the Lab Radar. Their new little one gives you BC on the display.

 

[cal30_sniper]

Hahahaha, definitely not small form factor in the rifle!

I was talking about the Lab Radar. Their new little one gives you BC on the display.

ooooooh, I thought you were taking a jab at my obscene caliber choices, haha.

No, it's the old school labradar. I had it set up to take downrange velocity readings at 25, 50, 75, and 100yds. It can't get the smaller .223-.308 bullets reliably at 100yds, but it picks up the .358s okay out there.

 

[hereinaz]

I’d never make fun of a man who is crazy enough to take 30 rounds from a big boy like that!

Who knows what he’d do in a fight!!! Hahahaha

 

[Jordan Smith]

I've spent some time measuring BC values using the LR. I would suggest you measure more than one sample (assuming that's what you did with the 108 ELD-M). A sample size of 10 is much better, and 30 is getting fairly reliable.

Carefully adjusting the parameter settings and aiming the LR will allow me to get readings out to 100 yards with 6mm bullets, and sometimes even .224" bullets.

Other than that, it's good to keep in mind that measuring the BC value at 100 yards is a poor representation of the BC value at lower MACH numbers, but should work okay out to a few hundred yards.

 

[cal30_sniper]

I've spent some time measuring BC values using the LR. I would suggest you measure more than one sample (assuming that's what you did with the 108 ELD-M). A sample size of 10 is much better, and 30 is getting fairly reliable.

Carefully adjusting the parameter settings and aiming the LR will allow me to get readings out to 100 yards with 6mm bullets, and sometimes even .224" bullets.

Other than that, it's good to keep in mind that measuring the BC value at 100 yards is a poor representation of the BC value at lower MACH numbers, but should work okay out to a few hundred yards.

Thanks for the feedback!

I was doing 10 each for sample size on the .358 bullets I was trying to measure.

I tried to measure 10 of the 108 ELDMs also, but the LabRadar was doing LabRadar things and I didn't realize it wasn't picking up my suppressed shots until the last round in the string. I figured it was value added as a sanity check if nothing else.

 

[Jordan Smith]

I wrote some Python code to analyze drag coefficients and BC values based on LR velocity measurements, and here's some select data points measured at 0.66 RH, 8.3 deg C, 26.2400001142 InHg. Keep in mind that measurements taken over shorter distance are less reliable, and Hornady's published values are measured much further than the distances over which I measured, so my values are generally higher.

It's quite obvious that there's some significant variation in BC values, partially due to the measurement uncertainty in the LR. A difference of even 1 fps at 90 m corresponds to about a value of about 0.003-0.004 G7 BC and 0.006-0.008 G1 BC.

Measured at 90 m, 2935 fps at 0 m, 2828 fps at 90 m:
7mm 180 gr ELD-M: The G7 BC value is: 0.401
7mm 180 gr ELD-M: The G1 BC value is: 0.802

Measured at 70m , 2932 fps at 0 m, 2850 fps at 70 m:
7mm 180 gr ELD-M: The G7 BC value is: 0.408
7mm 180 gr ELD-M: The G1 BC value is: 0.816

90, 2946, 2828:
7mm 180 gr ELD-M: The G7 BC value is: 0.364
7mm 180 gr ELD-M: The G1 BC value is: 0.728



70, 2892, 2787:
6mm 115 gr DTAC: The G7 BC value is: 0.309
6mm 115 gr DTAC: The G1 BC value is: 0.618

70, 2846, 2744:
6mm 115 gr DTAC: The G7 BC value is: 0.332
6mm 115 gr DTAC: The G1 BC value is: 0.660

70, 2869, 2764:
6mm 115 gr DTAC: The G7 BC value is: 0.306
6mm 115 gr DTAC: The G1 BC value is: 0.613

70, 2859, 2757:
6mm 115 gr DTAC: The G7 BC value is: 0.333
6mm 115 gr DTAC: The G1 BC value is: 0.663

50, 3118, 3040:
6mm 115 gr DTAC: The G7 BC value is: 0.322
6mm 115 gr DTAC: The G1 BC value is: 0.644



70, 2928, 2831:
6mm 108 gr ELD: The G7 BC value is: 0.339
6mm 108 gr ELD: The G1 BC value is: 0.678

50, 2923, 2852:
6mm 108 gr ELD: The G7 BC value is: 0.332
6mm 108 gr ELD: The G1 BC value is: 0.664

70, 2907, 2801:
6mm 108 gr ELD: The G7 BC value is: 0.308
6mm 108 gr ELD: The G1 BC value is: 0.615

70, 2938, 2832:
6mm 108 gr ELD: The G7 BC value is: 0.311
6mm 108 gr ELD: The G1 BC value is: 0.622

70, 2909, 2801:
6mm 108 gr ELD: The G7 BC value is: 0.302
6mm 108 gr ELD: The G1 BC value is: 0.604

70, 3018, 2916:
6mm 108 gr ELD: The G7 BC value is: 0.332
6mm 108 gr ELD: The G1 BC value is: 0.665

50, 3036, 2986:
6mm 108 gr ELD: The G7 BC value is: 0.491
6mm 108 gr ELD: The G1 BC value is: 0.983

50, 3068, 2997:
6mm 108 gr ELD: The G7 BC value is: 0.349
6mm 108 gr ELD: The G1 BC value is: 0.697

70, 3040, 2934:
6mm 108 gr ELD: The G7 BC value is: 0.322
6mm 108 gr ELD: The G1 BC value is: 0.644

90, 3071, 2934:
6mm 108 gr ELD: The G7 BC value is: 0.322
6mm 108 gr ELD: The G1 BC value is: 0.644



90, 2727, 2624:
6.5mm 147 gr ELD: The G7 BC value is: 0.404
6.5mm 147 gr ELD: The G1 BC value is: 0.804

70, 2720, 2635:
6.5mm 147 gr ELD: The G7 BC value is: 0.386
6.5mm 147 gr ELD: The G1 BC value is: 0.768

90, 2728, 2615:
6.5mm 147 gr ELD: The G7 BC value is: 0.373
6.5mm 147 gr ELD: The G1 BC value is: 0.741

90, 2732, 2634:
6.5mm 147 gr ELD: The G7 BC value is: 0.432
6.5mm 147 gr ELD: The G1 BC value is: 0.859