Shorty, I have a question that comes from not knowing. Online ballistics calculators produce velocity figures at different distances, but whether they are accurate is another thing.
With the Labradar and .22LR what does the data concerning velocities obtained downrange, say at 50 or 75 or 100 reveal? I understand it can be used to calculate bullet BC variation, but is there anything else?
I ask because I have a Labradar that I bought new but have never tried out once the Garmin became available. Perhaps there's a useful purpose for the Labradar.
A ballistic calculator's results are only as good as the numbers it is fed. If the box says bullet XYZ should have a BC of 0.150, but maybe that lot number happens to have bullets that are dinged up a little or misshapen in some other regular way, and the result is the actual average BC for that lot number is only 0.125 rather than the advertised 0.150, then naturally you're going to see actual velocities stray downrange from what the calculator figured they should be. It is also going to affect how much wind drift you actually get. So you might be puzzled with the initial results that you see on paper versus what the calculator gives you. If you measure the actual BC of a decent sampling of a given lot number then you can determine an average BC value that you should be using with the calculator, rather than the published figure, and that way you should get results out of the calculator that better match what you actually see in the real world with that lot number.
The velocity tracks that you get for each shot can be useful if you wish to have another metric by which to evaluate the quality of a given lot number. Yes, this data allows you to calculate the actual BC of every bullet. With that in hand you can then calculate the SD of the BCs, and that allows you to characterize the rounds in another useful way. The mean of the BCs tells you about the overall quality of the bullet design when you compare brand/model ABC to brand/model XYZ. And the SD of the BCs tells you about the consistency of bullet shape, how similar they all are to each other. That can give you a hint about how a given manufacturer's production line handling treats the bullets throughout the process. The larger the SD of BC, the more they're probably getting beat up.
The muzzle velocity SD can help you gauge how consistent some components of a lot number are. I mean, really, that relates to all the various components. Brass thickness affects it. Primer compound consistency of amount affects it. Primer compound consistency of mixtures affects it. Powder amount consistency affects it. Powder mixture consistency affects it. Bullet lube amount consistency and mixture consistency affects it. Even bullet shape and size affects it. The more consistent all those things are, the smaller the muzzle velocity SD will be. That's one part of the picture, but only gets you to the muzzle.
What happens after you leave the muzzle is where the size, shape, and makeup of the bullet comes into play. All those things affect how it interacts with the air as it travels to the target. And this is where the BC value comes in, and when you're considering a group of bullets then that's where you'll be interested in the SD of the individual bullet BCs. The smaller the SD of BCs is, the less variation there is in flight characteristics, which should lead to less dispersion.
The thing is, in order to get accurate comparisons you also need to keep fairly good track of temperature, humidity, and barometric pressure values. Comparisons of bullet data gathered a day apart, a week apart, months apart, etc., only really make sense if you know all of that atmospheric data because, of course, they affect the outcome. You need to keep track of that stuff as it relates to each LabRadar series. And Labrabaco will help with the comparsons. You punch in the atmospheric data and select the appropriate drag model, RA4 for rimfire, and then give it one of the LabRadar track files. It will tell you a bunch of stuff about each bullet as well as the whole series.
https://bc.geladen.ch/labrabaco/labrabaco.html
That website's been running for many years and probably isn't going anywhere, but if it ever goes down I have a version that can be run locally. Actually, I suppose the local version might also be helpful if you're checking this stuff out while you're still at the range but have no internet access.
I use Lapua's iOS ballistics app for when I'm shooting silhouette. When I last bought ammo for silhouette I snagged a case of Eley Club for warm weather shoots and a case of Eley Club Biathlon for cold weather shoots. They perform fairly differently from each other, so I need different scope settings for each. The scope numbers the Lapua app gives me from shoot to shoot with the same lot number also change a little bit. And having a more accurate BC number to feed the app also helps. Since it only supports G1 and G7 drag models I found I also had to do some fudging/trueing in order to get good results. I haven't really looked, but if there's an app that supports the RA4 drag model it would be a little better again. If things were really ideal, we could actually build a custom drag model from LabRadar tracks for each bullet and/or lot number, haha.
