Highest Velosity for SUBSONIC loads

[jcdflint]

I'm new with 300 blk. What the highest velocity for subsonic loads. I been loading Sierra 110 HP (20.0 of H110) for coyotes with much luck..but would like to try a subsonic load for the fun of it Thanks ...Jeff

[dellet]

Depends on where you will be shooting. During the summer months in Libya you could get away with 1180 fps.

Winter in Siberia on the other extreme it would only be about 900 fps.

1050 fps is a good safe number that will give you some room for the velocity fluctuations that always happen. They will be noticeably quieter around 1000.

Temperature is the biggest factor for the changing speed, colder is a lower threshold.

[jcdflint]

Thanks dellet ...

[cdl]

The speed of sound in air is mostly temperature dependent, but since the air over the bullet speeds up as it compresses in front of the bullet, near sonic, but still subsonic bullets can still crack. In practice it's not so much a particular speed as a range above the standard deviation of the load where things start to get noisy and then too noisy for you. I like to load to an average velocity around 1000 fps.

In my ballistic spreadsheet I use this formula as a guide:

Speed of sound(fps)=(331.4+0.6*_TC)*3.28084

where _TC is the Temp in Celsius.

[Netpackrat]

Yeah... Yesterday at the turkey day family gathering, we were plinking .22s at the hillside but had to curtail our 300 Blackout shooting, because it was cold enough for the Remington factory subs (green/yellow box) to go supersonic out of a 9" barrel. The temperature got down to about 7F while we were there.

[jcdflint]

Thanks everyone

[ncorry]

The speed of sound in air is mostly temperature dependent, but since the air over the bullet speeds up as it compresses in front of the bullet, near sonic, but still subsonic bullets can still crack. In practice it's not so much a particular speed as a range above the standard deviation of the load where things start to get noisy and then too noisy for you. I like to load to an average velocity around 1000 fps.

In my ballistic spreadsheet I use this formula as a guide:

Speed of sound(fps)=(331.4+0.6*_TC)*3.28084

where _TC is the Temp in Celsius.

So if I'm doing the math right, at 0F, speed of sound is 1,052, at 25F, it is 1,079, and at 100F, it is 1,161? That makes sense. Thank you for that formula.

[rjacobs]

So if I'm doing the math right, at 0F, speed of sound is 1,052, at 25F, it is 1,079, and at 100F, it is 1,161? That makes sense. Thank you for that formula.

I believe you are correct. Thats why MOST people shoot for 1050 because under "most" conditions any of us would encounter, they will stay subsonic.

[sirgknight]

Technically the speed of sound is dependent on several factors including medium, density and temperature. The speed of sound is 761 MPH (1116 fps) @ sea level with a surface temperature of 59 degrees. Not only does temperature affect the speed of sound but altitude and air pressure play a big part also. If you are shooting in Colorado the speed of sound will be different from shooting in Florida. And, as the air pressure changes (from high pressure to low pressure) the speed of sound will also change. Here our altitude is 256 ft so basically anything under 1100 fps will not break the sound barrier either in winter or summer.

[Dr.Phil]

1050 fps is a good safe number that will give you some room for the velocity fluctuations that always happen. They will be noticeably quieter around 1000.

This...
I use 1050 as my upper threshold.
My target velocity for hand loads is 1,000 fps using 70F, @ 12ft sea level.