Update note 20Oct20: Forum member fritz pointed out below that Hornady’s claimed ballistic coefficient for the 147 grain ELD Match bullet seems to be higher than it actually is. As I discussed below, when BC values obtained by ballistician Bryan Litz are used in the JBM calculations rather than Hornady’s value which I used for the table in this post, its results are much closer to the Applied Ballistics calculated results.
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Something that I have often wondered about is how accurate are the ballistics calculators we use and now that I have a LabRadar chronograph, how much can I trust its measured velocities.

The below figures are the measured and calculated velocities of a few shots of Hornady 6.5 Creedmoor 147 grain ELD Match ammunition from a Tikka T3x Tac A1 rifle with 24 inch barrel. If you want to check the calculations yourself, atmospheric conditions were air temperature 53°, station pressure 21.21" Hg, relative humidity 20% RH, all measured with a Kestrel 5700 weather monitor. (The accuracy of the below calculated values was also of course affected by the accuracy of the atmospheric measurements.)

The first bolded MV figure was the measured muzzle velocity per the LabRadar.
The second was the measured velocity at 100 yards* per the LabRadar.
Figure three was what the Applied Ballistics solver calculated the 100 yard velocity should have been using the given muzzle velocity.
Figure four was what the JBM solver calculated the 100 yard velocity should have been using the given muzzle velocity.

MV: 2513 // 2410 // 2419 // 2423
MV: 2563 // 2464 // 2468 // 2472
MV: 2548 // 2452 // 2454 // 2458
MV: 2544 // 2448 // 2450 // 2454
MV: 2547 // 2444 // 2453 // 2457
MV: 2550 // 2453 // 2456 // 2460

The figures indicate that the Applied Ballistics calculations more closely matched the measured velocities at 100 yards than did the JBM. The JBM was, however, very close, and because its calculated velocity outputs are given to the nearest 0.1 foot per second, I rounded the JBM figures to the closest whole value.

One difference between the JBM and Applied Ballistics calculators is that JBM uses published G7 ballistic coefficients and the Applied Ballistics uses custom measured drag curves for bullets in its library. I believe the custom drag curves are probably somewhat more accurate than claimed ballistic coefficients.

All in all, however, and despite the small sample of six shots, I was impressed with the close agreement of what the LabRadar measured at 100 yards and the expected velocities at 100 yards as calculated by both solvers.

*That’s one nice feature of the LR. Its doppler radar will measure downrange velocities as well as at the muzzle—sometimes, anyway. Downrange readings aren’t obtained for all shots. In this case I fired 10 rounds and got six 100 yard velocity readings.

This message has been edited. Last edited by: sigfreund,

I think ballistic apps are garbage. I have played with Applied ballistics, JBM, Shooter etc... The same data used in different apps yields data for a 1000 shoot ranging from U25-U39. I have never been able to get close to my rifles actual performance on 1000 yard shot where the actual up adjustment is around U31.

As to your post I am curious about lab Radar recording data out to 100 yards. Have you used that data in longer shots on ballistic apps and verified results out to longer ranges nearing 1000 yards?

I've experienced the same with mine. I can typically get good readings until about 6o yards or so and then it falls off. Probably has to do with my lack of precise alignment to the target more than the unit. 100 yard data is typically not important to me.

AS to the accuracy of the Labaradar, if you trust its reading at the muzzle, Id trust it at 100.

quote:

Originally posted by gw3971:
Have you used that data in longer shots on ballistic apps and verified results out to longer ranges nearing 1000 yards?

I’m not sure if I understand your question, but I haven’t done anything with the 100 yard velocity figures except as described above.

I have had mixed results with the ballistics calculators I’ve used over the years. In retrospect, though, I believe most of their significant failures to give me the correct dope for longer distances was due to bad input data.

For example, when I first started comparing LabRadar data to older velocity measurements with my Oehler chronograph, I became convinced that there was something wrong with the Oehler because of the large discrepancies in some measurements by the two. Ultimately, however, I realized that the variations were due to the ammunition itself, and both chronographs were telling the truth. Yes, that should have been the first thing I thought about and questioned, but it didn’t occur to me that the differences among lots of the same loads would be so large.

I’ve also come to suspect that some problems might be with my sights. I haven’t tried to confirm if any have significant tracking errors, but that seems to be very common and is something I should do. I’ve just rationalized my own problems as, “Oh, surely that couldn’t happen to me.”

FWIW, though, the last time I went to the range with my 6.5 Creedmoor Tikka, I used the Applied Ballistics dope from my Kestrel, dialed it on my scope, and scored a first-round hit on an 8-inch plate at 600 yards. That was followed by several more in succession, and I scored several more hits where I was aiming at 540 and 300 yards using the AB dope.

IMO the start of this process is picking a bullet with a BC that is well establish and stable. Hornady's 147 ELD-M ain't it. Your data would almost certainly be different if you used Hornady's 140 ELD-M bullet -- it's my understanding that Hornady's published BC is accepted by most ballistic calculators as accurate. Not so much with the 147 ELD.

I first discussed the 147's overstated BC on this site in late spring or early summer 2019. This was after I had horrible results in a Raton, NM ELR match. My experience was echoed by a shooter right next to me, who ixnayed the 147 ELD bullet for SMK 150 in his 6.5 PRC. A month or so later, a shooter at Nightforce's Wyoming ELR match found out the hard way during the match the the 147 ELD doesn't fly as published by Hornady. Sigfleund -- I recall your weighing in on this discussion.

I also discussed the 147's overstated BC in another thread sometime earlier in 2020. I recall that this was your thread, sigfreund. You stated that the flawed BC shouldn't be an issue, as you didn't expect to shoot the 147s at any kind of long distance. More likely, 300 yards maximum, but probably most at 100-200 yards, IIRC. In this year's Nightforce's Wyoming ELR match I helped two shooters on the practice line with 6.5 PRC 147 ELD loads. They couldn't figure out why their bullets were flying so low. I don't know if they figured things out by the time the match started.

In my rifles, Hornady's 147 ELD load is really quite accurate, with reasonably good SDs. I found the MV lower than expected on one lot, and of course the published BC is overstated. I have a handful of boxes of ammo in my inventory, which I only use on positional shooting at moderate distances, where positional stability is more important than flight curves.

Applied Ballistics flight model most likely does use a lower BC than JBM. Which is good for AB, bad for JBM. This is almost certainly explains your velocity numbers at 100 yards. However, relative velocities at 100 yards for modern bottle-necked cartridges really mean nothing to flight curves at 100 yards. It's just too close.

JBM uses a lot of the Applied Ballistics data. One just has to look for bullets listed with Litz in parentheses in the bullet drop down menu. I've run the calculations for bullets I use which have both regular and Litz references. The predicted ballistics differences are generally miniscule, even at distances of 800 to 1000 yards. The differences are generally smaller than my level of accuracy. I recall one 308 bullet's being different by 1/4 MOA at 1000 yards -- an accuracy I can't shoot to.

Again, go back and try your experiment with 140 ELD. I bet the data differences will be much smaller.

*****
On a different note, your first MV of 2513 is really odd. If that's from the same lot as the other shots, then that was a bad load. Or your MV reading wasn't good. I don't see that kind of MV spread from a single manufacturing lot.

Your MV's also seem a little slow. Measured 147 MVs on my 26" Bartleins with a TBAC can. Both barrels #2 and #3 were around 2,750 fps with my first lot. The second lot clocked in around 2,740 early on with barrel #3, then jumped to almost 2,800 when the barrel finished speeding up -- although that was on a really hot day.

quote:

Originally posted by gw3971:
I think ballistic apps are garbage.

JBM works well for me. I don't know how many years I've used it, but I'm guessing at least 10.

I've used JBM for 223 Remy, 6 Creedmoor, 6.5 Creedmoor, and 308 Win. The data is amazingly accurate for my rifles, as long as the accurate data input occurs. I use Magnetospeed muzzle velocities. I use Density Altitude, as measured by Kestrels. I don't use actual altitude, station pressure, or humidity -- I let the Kestrel calculate DA, and JBM works well with DA.

And JBM also does well with 22lr -- which I've shot out to 300 yards. The challenge here is the MV variation inherent with many 22lr loads, even the more expensive match-grade loads.

Depending on the rifle and bullet, JBM has been good for 223 out to 700 to 900 yards -- using Sierra and Hornady bullets. This means it's working for velocities down to Mach 1.0 and sometimes a little less.

With 6 Creedmoor I've only shot and predicted flight out to 700 or so yards. JBM worked well. This distance isn't all that much of a stretch for an accurate 6CM load, however.

With 308 Win I've shot out as far as 1200 yards with good results via JBM, again with Sierra and Hornady bullets. JBM was spot on. The bullets were definitely moving at subsonic speeds by this point.

With 6.5 Creedmoor and 140 ELD-M bullets, I shot many times out to 1800 yards. JBM does very, very well out to around 1300 yards. Beyond that, I need to add elevation -- about 1 MOA for 1400 yards, 2 MOA for 1500 yards, and 3 MOA for 1600-1800 yards. Beyond 1800 yards, I need about 4 MOA of additional elevation -- which worked on a target at 2100 yards this summer. This means that JBM predicts 140 ELD well down to transonic speeds, but struggles with the transonic-to-Mach 1 region. I suspect the 140's BC drops off faster than expected at slower velocities.

quote:

Originally posted by fritz:
the 147's overstated BC

Hornady lists the G7 BC as 0.351, and that is what I used in the JBM calculations reported in the first post. Litz, on the other hand says 0.335 average 1500-3000 fps, and 0.342 for 2500-3000 fps. For 2000-2500, Litz gives 0.332. Using 0.342 with the JBM does bring the calculated velocities at 100 yards closer than what I posted above, but not quite what was measured or as close as the Applied Ballistics figures. If I split the difference to 0.337, then JBM’s results are virtually the same as the AB’s.

Thanks for the comments and reminder to not automatically accept manufacturers’ BC claims.

Regarding the LabRadar, it is of course a <$600 unit, not a laboratory instrument, and therefore may not be absolutely accurate. But the muzzle velocity and velocity at 100 yards are two separate measurements, the second of which agreed very well with the two ballistics calculators. And as I mentioned, Bryan Litz has switched to using LabRadar units, so that’s a pretty strong implied endorsement. But if, for example, the recorded 2513 muzzle velocity had been coupled with a reading of 2450 at 100 yards, i.e., the same general value as the other shots, rather than 2410, I would have been very suspicious of a measurement error at the muzzle.

All this makes me confident that the chronograph is giving me reasonably good results.

The other undiscussed issue is that the LabRadar data has an error tolerance. They say +_.1%. If you include that the correlation on the calculators is pretty darn good to me. Longer ranges of course TBD.

quote:

Originally posted by gw3971:
I think ballistic apps are garbage. I have played with Applied ballistics, JBM, Shooter etc... The same data used in different apps yields data for a 1000 shoot ranging from U25-U39. I have never been able to get close to my rifles actual performance on 1000 yard shot where the actual up adjustment is around U31.

Guessing bad input data. The above apps track well for me. Post all your inputs.

This thing https://www.autotrickler.com/shotmarker.html gives MV at distance set up. Shot through it at 545yds, LabRadar at the muzzle. Shotmarker MV was with in a couple feet per second of predicted AB MV. So we know the velocity at the muzzle and at the target. The little vertical spread of my 6BRA on target at 545yds track the velocity differences? No!

quote:

Originally posted by offgrid:
This thing ....

Wow! Looks very neat.

quote:

Originally posted by offgrid:
This thing https://www.autotrickler.com/shotmarker.html gives MV at distance set up. Shot through it at 545yds, LabRadar at the muzzle. Shotmarker MV was with in a couple feet per second of predicted AB MV. So we know the velocity at the muzzle and at the target. The little vertical spread of my 6BRA on target at 545yds track the velocity differences? No!

We have been using these Shot Markers at the club for a couple of years. We've had Adam come down and play with us and we learned a lot about these devices. Just FYI, Adam will be the first to tell you to not completely trust the MV figures at the target. I found out more about how the system works than I ever wanted to know and what environmental factors do to the system. It's an amazing piece of applied technology.