FAC air @ 3300 feet

[greenanchor]

Does anyone know what effects thinner air is going to have on
21grain Bisley magnums set to run @ 920-930fps?
Will that muzzle velocity setting here in the UK differ when im at a higher altitude?
Wanted to pick your brains before i chairgun it
Thanks

[loiner1965]

Does anyone know what effects thinner air is going to have on
21grain Bisley magnums set to run @ 920-930fps?
Will that muzzle velocity setting here in the UK differ when im at a higher altitude?
Wanted to pick your brains before i chairgun it
Thanks

yes as air is thinner so less resistance.....not sure if you can work it out though

[Mark_T]

Does anyone know what effects thinner air is going to have on
21grain Bisley magnums set to run @ 920-930fps?
Will that muzzle velocity setting here in the UK differ when im at a higher altitude?
Wanted to pick your brains before i chairgun it
Thanks

Assuming propulsion pressure is a constant;

3300 feet equates to about 110 millibar pressure difference or 1.5psi. So there's a slight increase in force on the pellet so muzzle velocity would be higher.

Air density is about 8% less so pellet deceleration would be slighly less.

In practice the effects would be negligible but it would go further and faster.

[greenanchor]

Thanks for the replies, your thoughts confirmed by chairgun. Which is what i expected.
Really wondering if pellet stability will alter at all, i suppose its the actual gyroscopic action of the pellet that slings it out of sync at silly fps rather than the environment.....