Now I dunno WHAT this thing "measures" or reads but in my case it's eminently repeatable.
Al, I'm not sure what it measures either. Except it does a real good job of measuring how far away something is. So, the question becomes, "how to use it."
OK, put the base against the stop, and move the stop so that the sonic head is at the beginning of the ogive of the bullet. That'll tell you how long the shank is,
relatively speaking, quicker & more accurately than any caliper setup. Unless it has a boattail, then you don't know if it's the boattail or the shank, unless you check boattails first......
Back with Sierra bullets, you could measure how concentric the boattail was, where the ogive began, and how true the point was running. For me anyway, the long, long VLD bullets with long boattails meant the little balls the bullet rides on weren't spaced quite right. Anyway, back in the late 1990s, Sierra had just come out with the 142-grain 6.5s, and Joel Pendergraft & I each had one. We soon discovered there were two different lengths, even within a box. They were quite consistent, just
different. We sorted as above, & we won a lot of wood with those rifles & bullets.
More or less the same time frame, Charles Bailey took three readings on all his long-range bullets. These were Berger 210 VLDs. Don't know how he got them to fit, but he did (CB was also a master machinist, he might have gone inside the housing & re-located them.)
Anyway, he had his A sort & his B sort (and then "others"), and the difference with the B's was usually in the nose, that old "fishtail" nose you'd get with Bergers during the years between when Walt sold the company & bought it back. CB just filed down the nose on that "B" sort. He'd made a jig, I guess this was an early form of "meplat trimming."
Now, I duuno if it counts for "proof," but he won Shooter of the Year with these sorts one year, and the year before, would have, except for a disastrous Nationals. Remember, these are the years when Walt didn't own Berger bullets, and his sorts gave him about a 50% yield into A + B, the rest being the dreaded "others"). Now, Charles Bailey never did much unless he'd proved it mattered, by firing a lot of bullets at long range. Sort of like Lee Fischer in that regard.
CB then went to 187-BIBs, and stopped using the Juenke. Both he & I found it too boring with BIBs -- they were that consistent. Except now I use it, after meplat trimming & repointing, for shank length only...
Anyway, the key, I think, is to use it to measure small distances, in a
relative manner. Whatever you think matters. Then test to see if it does matter.
I followed the instructions in the manual to the T, however, it sure doesn’t do what the manual indicates. I’m sure it’s just me doing something wrong. 