Buckle up, ski bunnies, we're going on a trip.
I have also been running the Garmin side by side with the Athlon and would like to pick your brain on a couple of things. I am still using release firmware on the Athlon BTW, I will be updating it before my next range session but was initially hesitant based on the fact Garmin had updates where their unit operated quite poorly relative to the release firmware. Last range session I had a few mis-reads though so I'm going to update now.
I think the firmware updates have partially fixed the offsets I experienced, and I hope future firmware updates completely eliminate them. My first few days on the line with the Athlons against other brands saw teens to 20's high or low, on every session. Now, the issues seem to only occur 1/4-1/3 of sessions, more often high than low, and typically LESS offset when low than when high (so low offsets might be 5-7fps, high offsets might be 10-25fps). It's better than it was originally in May, but not quite where I feel they need to be quite yet.
1) Do your Athlon units operate well in the 4"-10" distance from the muzzel range the directions indicate? Mine misses shots when its that close and seems to want to be 20+ inches behind and to the side. I have not mounted mine to the rifle, are you getting good results in that configuration?
I can't say I have noticed any specific issues with position of the Athlons - or the Garmins, or the LabRadar LX's either for that matter. By and large, I don't worry about it, I put them where I want them, and they pick up shots.
For all of my comparison testing, I've made sure they were all at least laterally within the proper width to the sides, such as using that fixture I have pictured below.
Here is a shot of the first time I did a side-by-side comparison with the 3 brands (brake blast knocked over one of my Garmins). That's a 375CT rifle, so the units are well behind the muzzle by more than 10", and I'd be certain the outside units are more than 10" wider to the side as well, since I know that bipod mat is wider than 21". But they all read - when they weren't knocked over.
I'd done this quite a bit with my Garmin over time, so I tried it with the Athlon, and it also worked - I can stand behind shooters, likely 10-15ft behind the muzzle and 3-4ft above bore and pick up shots just by holding the Garmin or Athlon like a GoPro.
Going the opposite direction now, and getting closer to the gun: I built this rig to control position during the bulk of my comparative testing work, all of the small units are positioned within the boundary of the 10" limit from the barrel, and have hundreds of rounds fired in this way.
I shared on this forum my Static vs. Gun Mounted test results - showing the difference in muzzle velocity reading when mounted to the rifle vs. to a tripod. In this photo, you can't see the second Athlon mounted on the far side of the rifle - the tension knob of the arca mount its on is visible; the green knob in front of the Garmin & LabRadar mount.
Opposite side view while my son was setting up the Athlon on the gun mount.
So I guess I just haven't ran into any issues with placement which would give me concern - so I don't concern myself with it. HOWEVER, I AM working now on a series of tests which will let me watch the sensitivity of the units to direction of aim and relative unit position to the muzzle, both in ability to pick up shots as well as the influence of angle and position on the measured velocity.
2) When you say the Athlon is not showing as good of an SD and ES and that the data is more volatile, are you seeing something like 1-2 shots out of 50 that are off by 100fps and the rest of the shots fall in a similar pattern to the Garmin or does the overall spread look wider? How much difference are you seeing between Garmin and Athlon SD and ES numbers in a data set? Do you think were are talking random individually misread shots, systematically less precision, or both?
Actually, my personal perspective about my observations of this data is that "its really fucking weird," but I can tell it's systemic noise, not random bad readings. It is NOT 1-2 shots which are off by 100fps, and the easiest answer to that is that the ES and SD aren't artificially higher than expected, and are not spread inappropriately. I'm talking about the actual data volatility, not simplified metrics.
TLDR version: Irrefutably, no, this is not 1-2 shots which are off by 100fps, and is not being caused by a few random mis-readings. These data sets pass all of the common heuristic tests to confirm that the ES's and SD's fall within expected ~4.5-5.5x ratio between ES and SD, and frankly, that "really fucking weird" part is the fact that the ES's and SD's aren't even materially different in most cases - but when I visually inspect the plotlines for these sample sets, I can see higher volatility. These data series all follow a Normal Distribution trend, and my data sets, which I've shared in their entirety for the comparisons I have published, are NOT being skewed by a few bad readings. This is systemic volatility, and the fact the Athlons are reading considerably higher volatility than the other two brands suggests it is a lower SNR than the other brands - more noise, less accuracy.
That's all kind of hard to put into words, but:
1)
Variability between 2 units of the same brand, and possibility/impossibility to achieve potential +/-0.1% accuracy specification: I have fired several hundred rounds in testing with 2 each of Athlons, Garmins, and LabRadar LX's side by side, as pictured above in that holding fixture. This didn't give me a direct means of measuring how close any chronograph would be to "truth," but it DOES give me defensible evidence that a brand would be FAILING to be within their specified +/-0.1% accuracy to "truth." If both units of a given brand were always within +/-0.1% of "truth," then the two units could never be more than 0.2% of the MV apart, otherwise we KNOW that at least ONE of them, or BOTH, must be more than +/-0.1% "wrong" from truth. The FARTHEST they could ever be from "truth" is 0.1%, then if one is as slow as it could be and still be "true," and the other as fast as it could read and still be "true," then they can only be 0.2% of the MV apart.
So I tested that...
This is a 100 round rimfire data set with ~1085fps average, so the +/-0.1% expectation means we can only be +/-1.1fps, or only be 2.2fps apart for each brand, or we know at least ONE of them is not reading within specified accuracy to "truth". The Garmins were never more than 1.5fps apart over 100 rounds, which is within the possibility that BOTH units are reading every shot's true value, within 0.1%. The LabRadar LX's farthest spread between the 2 units was 4.68 fps (they read to the 1/100ths digit), which is slightly more than 0.4% apart, outside of the +/-0.1% claim by more than double, meaning at least one, if not both were NOT displaying the true speed. The Athlons also had a max spread between the two of 4.6fps, again, 0.4% of the MV from one another, such it is impossible that both units could be reading within +/-0.1% of the true speed. But never in those 100 rounds were the Garmins outside of 1.5fps apart, meaning both COULD be displaying the true speed, within their specified +/-0.1%.
Another 100 round rimfire data set where the Average was 1200fps (coincidentally exactly), again, +/-0.1% corresponds to a span between 2 units never being more than 2.4fps, the Garmin achieved this, the LabRadars missed by about 50%, so just outside of +/-0.15% apart, but the Athlons were 6.5fps apart, which would be equivalent to +/-0.27% spread, not 0.1%...
Here's a 2805fps average centerfire dataset analysis - 51 rounds across the Garmins and Athlons, but I missed just enough shots that I could only reconcile 39 rounds with the LabRadars. 2805 Average means +/-0.1% is 5.6fps spread to be within tolerance, and again, ONLY the Garmins achieved that potential, with the max spread only being 2.8fps between the two. The LabRadar's were 15.2fps apart, which would be in the +/-0.3% ballpark, and the Athlons were as far apart as 19.4fps apart, meaning roughly +/-0.4% band. The AVERAGE difference between the two Athlons was outside of the +/-0.1% tolerance, effectively, we know that for at least 25 of the 51 shots, the Athlons were outside of their specified tolerance to truth.
Comments to these data sets:
--> ALL of these velocities COULD be "wrong," and at least ONE of each brand COULD be right, but we can note that it simply isn't possible for BOTH to be within their spec for proximity to "truth" if we have more than twice their spec between their readings, so ONLY the Garmins COULD both be right in these tests, and we know at LEAST ONE of the Athlons and LabRadars are wrong, if not both.
--> If you note the Max vs. STDEV spreads, each ES is roughly 4-5x the SD for all 3 brands in all 3 of these experiments, which is typical of a Normal Distribution Sample Set, so it's not a matter of the brands reading one or two bad readings and making big, false ES's, this is simply systemic noise indication.
2)
Visual inspection of data plotlines for volatility observation: It's relatively quick and easy to plot these data sets and visually inspect for outliers which might skew the results. Again, I ran the quick and dirty heuristic test as to whether the ES and SD ratio made sense for a Sample Set which followed a Normal Distribution or not (they all do), but I also plotted these data strings to allow visual confirmation. Because the data strings inherently cross back and forth (velocity high, velocity low, high, low, etc), I re-ordered the data based on increasing Average Velocity (average of all 6 chronos), and re-plotted. We can see a smooth curve produced with no random outliers for any of the 6 chronographs, and tracing a Normal Distribution, center weighted trend with high and low tailings. This re-plott allows us to look for random spikes and "bad readings," and evaluate the distribution of the datasets as well as evaluate the systemic NOISE and VOLATILITY of the datastrings, beyond the distilled ES and SD data. And here, we see higher volatility from the Athlons than from the Garmins or LabRadars.
So I wanted to see if the large number of samples in the set could be hiding 1-2 big flukes and diluting their influence on the SD, so I looked for that...
Here's a 99 round rimfire set (CCI SV, if anyone is interested, which had SD's of 12.7-12.9 across all 6 units). The ES's measured by each of the 6 units were within 2fps of one another, ranging from 69.0 ES to 70.6ES, and again, all 6 units agreed the SD's were 12.7fps to 12.9fps. But when you look at the dataplots visually, the volatility behavior becomes more obvious. The Purple/Pink trends are Athlons, the Greens are Garmins, and the Oranges are LabRadars. In this plot, we see the Athlons were ~5fps high offset from the others, but also notice that the trendline is more volatile, rougher, more noisy. The Garmins had the tightest lines, bouncing within the peaks of the LabRadars, but the Athlons had notably more noise than the other two brands.
Here's the centerfire 51 round sample set mentioned above. In this dataset, the LabRadars were slightly low offset, 2-3fps slower in Average MV than the Garmins, and the Athlons were repeatedly offset 8-9fps higher than the Garmins. Again, the ES's were very similar, 42.5fps ES to 46.9fps ES, and the SD's measured by all 6 showed 7.9fps to 9.6fps. Really not much of a difference there (1.7fps difference in SD's, on units which should only be reading within +/-2.8fps of truth). But visually, again, we can see 1) there are no huge spikes from fluke outliers, and 2) these Purple lines are more noisy than the Green or Orange lines. (***Noting here, this plot is zoomed in, half as wide and ~17% zoomed for height, so smaller ES and SD looks more noisy than the plot above.***)
Overall, as I mentioned previously, I'm seeing substantially higher volatility in the Athlon results. They're still a better chronograph than any common optical chronograph on the market, and the lower cost of the Athlon compared to the LabRadar LX and the Garmin may make absolute sense for someone who isn't shooting ELR or doesn't rely upon comparing data from sessions which are separated by multiple days, but there's a performance difference I can measure right now. Firmware MAY fix this, and I'll keep testing over time to see if and when it does.