Effects of altitude on pressure.

[Alex Wheeler]

I have read that altitude has no bearing on muzzle velocity. I recently moved from sea level to 6000 ft. I swear I see pressure signs at much lower powder charges. I have not messed with my comp. rifles since the move, but I will know for sure when I do as I have detailed data on them. Any one notice this before?

 

[Varminteer]

I live at 7000 ft and our ice cream carton and potato chip bags are "swollen". Those items feel less pressure pushing in so they expand out.

Nothing scientific but most of my handloads are less then published maximum because pressure signs start to show early.

 

[KMart]

A chemical reaction is affected by 3 things. Temperature, pressure and time. You change any one of those factors and it changes the other two.

 

[Turbulent Turtle]

I seriously doubt the elevation change has anything to do with increasing pressures in your ammo. A cartridge case is a lot less influenced by the decrease in air pressure than a bag of chips.

I developed my load at sea level elevation and I took that load to Raton (6600+ feet ASL) two years in a row and I never saw any difference in the fired cases. I did notice the reduction in required drop adjustment.

 

[jlow]

I don't think it affects chamber pressure but it certainly affect MV at extended distance due to the thinner air and so lower air resistance.

 

[CatShooter]

I don't think it affects chamber pressure but it certainly affect MV at extended distance due to the thinner air and so lower air resistance.

How can it effect the muzzle velocity "at an extended distance"??

The muzzle velocity is the velocity AT the muzzle, not at an extended distance, which would be the "Extended distance velocity"??

 

[Nomad47]

Good catch, Catshooter. I think he meant to say velocity and not MV.

 

[Turbulent Turtle]

Or maybe he has a really LONG barrel.

 

[jlow]

Nice! ;D I hope I am not getting a sense of “length” envy here? LOL!

 

[Ringostar]

I haven't tried crono tests at higher elevation. However load work at our home range (Winnequah) changes when going to Raton or Ben Avery. With temps being equal, we get a 3.5 min elevation change. Also many have gotten pressure increases, and had to reduce their loads going to Ben Avery.

 

[Old Navy]

I haven't tried crono tests at higher elevation. However load work at our home range (Winnequah) changes when going to Raton or Ben Avery. With temps being equal, we get a 3.5 min elevation change. Also many have gotten pressure increases, and had to reduce their loads going to Ben Avery.

Where is Ben Avery? Later! Frank

 

[Nomad47]

Ben Avery is north of Phoenix, AZ, USA.

 

[Old Navy]

I haven't tried crono tests at higher elevation. However load work at our home range (Winnequah) changes when going to Raton or Ben Avery. With temps being equal, we get a 3.5 min elevation change. Also many have gotten pressure increases, and had to reduce their loads going to Ben Avery.

Where is Ben Avery? Later! Frank

Ben Avery is approximately 750' higher than Winnequah. I think you guys are loading on the ragged edge. When I plugged those elevation numbers into the JBM program I saw 1/2" difference in drop @ 500 yards. Later! Frank

 

[jlow]

I haven't tried crono tests at higher elevation. However load work at our home range (Winnequah) changes when going to Raton or Ben Avery. With temps being equal, we get a 3.5 min elevation change. Also many have gotten pressure increases, and had to reduce their loads going to Ben Avery.

Where is Ben Avery? Later! Frank

Ben Avery is approximately 750' higher than Winnequah. I think you guys are loading on the ragged edge. When I plugged those elevation numbers into the JBM program I saw 1/2" difference in drop @ 500 yards. Later! Frank

Better watch out, they are going to accuse you of having a "long barrel"! ;D

 

[Ringostar]

Frank, Where did you get your elevations from? I haven't been to Ben Avery yet, but hope to in Feb. I have shot at Raton. and the whole group from Wi had 3-3.5 min of elevation difference.

 

[Nomad47]

Ringostar,

The F Class prone position for 1000 yards at Ben Avery is 1642' AMSL - according to Google Earth.

 

[Old Navy]

Frank, Where did you get your elevations from? I haven't been to Ben Avery yet, but hope to in Feb. I have shot at Raton. and the whole group from Wi had 3-3.5 min of elevation difference.

I got them off my DeLorme Topo USA program. Later! Frank