My club approved shooting a pistol cartridge lever action rifle at our silhouette range that was designed for rimfire so long as the bullets are subsonic. To help ensure we adjust for the speed of sound with temperature I did a linear regression on the data.

Y = FPS
X= °F
Slope = 1.06
Intercept = 1053.9333

Equation: Y = 1.06 X + 1053.9333

We will set up a chronograph to certify the ammo. I'm shooting .38 Special Jacketed Hollow Point at 974 fps average and the rams haven't rung yet. It is what it is.

You could have used this https://www.weather.gov/epz/wxcalc_speedofsound

No1_49er wrote: ↑Wed Apr 17, 2019 7:53 pm You could have used this https://www.weather.gov/epz/wxcalc_speedofsound

No Internet at the range. That's where I got the six data points and saw that it was linear.

I shoot subsonic, rimfire, pc and big bore.

Charlie, as far as I know, it also depends on altitude.

You guys are pretty high up in your neck of the woods.

BTW, I've been only shooting subsonic for all three matches lately.

Are any of your people going to make the Regional match at LASC or the State match in Hat Creek?

Thanks, Dennis

dwostler wrote: ↑Thu Apr 18, 2019 1:40 pm Charlie, as far as I know, it also depends on altitude.
You guys are pretty high up in your neck of the woods.
BTW, I've been only shooting subsonic for all three matches lately.
Are any of your people going to make the Regional match at LASC or the State match in Hat Creek?
Thanks, Dennis

My home range is just below 3000 ft.
When I say sub-sonic I'm speeking stricly a theoretical 1140fps sea level speed of
sound.
It would not make sense otherwise.
Just saw my check was cashed, so yeah, I'll be there at LASC.
Tim

It sounds like the OPs club is more concerned with target damage than transonic instability.
If so, I don't quite understand the need for a temp chart.
It's not breaking the sound barrier that damages the targets.

Ojaileveraction wrote: ↑Thu Apr 18, 2019 2:54 pm It sounds like the OPs club is more concerned with target damage than transonic instability.
If so, I don't quite understand the need for a temp chart.
It's not breaking the sound barrier that damages the targets.

Not only target damage but the range and stands too. Since the subsonic upper limit changes with temperature it's not fair to use a fixed speed.

The scientist in me: The speed of sound is solely dependent on temperature. M = Square root of (γRT) where γ is the ratio of specific heats, R is the molar gas constant and T is the temperature in Kelvin.

I'm with Ojai on this. Who cares what the temperature is? Pick a max velocity, say 1100 fps, and go with it. Are you really going to set the max allowable velocity at every match depending on what the temperature is? Please, don't make this more complicated than you need to.

Sorry Tim, I had Charlie's name on my mind.

Glad to hear you are coming.

I haven't shot up in Ojai in many years, love the area.

Thanks, Dennis

DJA wrote: ↑Thu Apr 18, 2019 4:35 pm I'm with Ojai on this. Who cares what the temperature is? Pick a max velocity, say 1100 fps, and go with it. Are you really going to set the max allowable velocity at every match depending on what the temperature is? Please, don't make this more complicated than you need to.

I'll see your 1100 and raise you 50.