Is this more clear?
Do groups enlarge after bullets go through the trans-sonic region?
The speed of sound ~1125 fps.
See page 536 of the 2020 Gun Digest, (or the back of ~any gun digest). 22lr hv bullets, mv = 1255 fps, 100 yd v = 1016 fps. 22lr hv hp bullets, mv = 1280 fps, 100 yd v = 1001.
Looking at this page, see that all 22lr hv bullets go through the trans-sonic region between the muzzle and 200 yards.
If groups enlarge after bullets go through the trans-sonic region; then we would expect 22lr hv 200 yard groups to be larger than 22lr standard velocity, <1235 fps, groups.
We have much data about 22rf 200 yard 50 shot groups, here: https://www.rimfirecentral.com/forums/showthread.php?t=1129343
Armscor Precision 36 grain CPHP 22lr, mv = 1201, group size ~8.3”
Armscor Precision 40 grain SV 22lr, mv = 1060, group size ~13.8”
CCI AR Tactical 40 grain CP 22lr, mv = 1219 fps, group size ~10.2”
CCI Clean Polymer Coated 40 grain SV 22lr, mv = 1050 fps, group size ~9.1”
Review of the 50/200 data shows that there is NO large increase in group size with hv bullets over sv bullets, suggesting strongly that there is NO large increase in group size when bullets go through the trans-sonic region over those that do not.
There are two competing theories about the trans-sonic bullet story.
Some bullets at some velocities at some ranges become less accurate over a short change in range.
Ex: over a 10% increase in range, group size increases 20%. Over this 10% increase in range the bullets may or may not drop below the speed of sound.
There is general agreement that this occurs.
One theory contends that the bullet velocity dropping below the speed of sound causes the bullet to vary from their course and make big groups.
The other theory says that as the bullet RPM drops, the bullets becomes unstable and less accurate; and if it happens around the speed of sound-that is coincidence. (I have proven that slow twist barrels make ever larger groups as velocity falls, and can make it happen on demand.)
Exponents of both theories have no supporting data that I’ve been able to find.
Measurement of the 50/200 groups: measure group size with a plastic ruler with 1/10” graduations, measure 6” of the picture ruler with the plastic ruler. Group size ~ plastic ruler group size X (6/plastic ruler 6&rdquo.
If the picture group measures 4”, and 6” of the picture ruler = 3”, then the true group size ~ 4” X (6/3) = 8”.
If group size varies as the cube root of the number of shots / group, and it ~ does from n = 2-10; then 50 shot groups are 2.15 times the size of 5 shot groups.
If 100 yard group size is 2.4 times 50 yard group size, and if good 50 yard 5 shot group size = .5”; then 200 yard group size ~ 2.4^3 X .5 = 6”; the kind of numbers we see in the 50/200 data. Reality check.