Velocity problems

[Angel_Eyes]

I have used many powders and bullet weights and shapes in my reloading, (mainly for target shooting velocities) and have come across a strange effect.

When my experiments have brought my velocities within a few ft/sec of the speed of sound (1125 ft/sec) I have experienced odd behavior regarding the grouping of the rounds, flyers, tumbling and strange group sizes.
As long as I keep about 25-30 fps away from this speed, everything seems normal
This does not include B/P as I don't chrono these loads.
Has anyone else noticed anything like this? ( I shoot mainly indoors at 25 yards for these purposes).


AE ( puzzled.)

[Gun E Bear]

It's called the transsonic range and long range shooters stay away from it. It will do all kinds of unpredictable things to the bullet as it passes through this velocity range. Long range  shooters either stay below it, or above it all the way to the target. 

Gun E Bear

[Adirondack Jack]

Yep.  dwelling in the transonic range too long will rip an airplane to shreds, and makes bullets do weird things.

As ya linger at the sound barrier, ya get a ripple of turbulence on the side of the bullet.  If yer bullet leaves the muzzle above the speed of sound, that ripple (the thing that causes the crack) is behind the bullet, no issue.  if yer right close but haven't quite broken the barrier, that ripple can be at the back corner of the bullet, and like a car on the back corner of a NASCAR racer, can cause turbulence that can "spin out" the bullet or at least make it act goofy. Stay a shade slower or above the barrier all the way, yer in "clean" air.

  With airplanes not stressed for SS flight, it isn't breaking the barrier that hurts, it's slowing back down, as that ripple of turbulence catches up wiith the trailing ege of the wings and tail surfaces, and can "flutter" em right off the plane.....

With bullets, that same slowing through the transonic range is rough on accuracy, and is one reason for the design of boat tailed bullets.  For our purposes it's just easier to avoid the TS range altogether, either by launching at 1100 or less, or 1300 or more.

[Angel_Eyes]

My God, you guys are good!!

I mean, obviously, I knew all that, I was just testing you.

Well done, you passed!

Thanks, AE.