Originally Posted By: Jack RobertsThe elevation will not change the MV, but does make a big difference in down range performance. In the thinner air bullets do not slow down as quickly.
Jack
Because I'm anal, I'll have to disagree. The bullet has to push air out of the barrel when it leaves. The mass of this air is depends on atmospheric pressure.
So the propellant charge has to push the bullet, plus the air in the barrel out. And the mass of the air varies.
I decided to put on my nerd hat anyway despite my laziness. If my calucations are right, and I make no guarantees, the mass of air in a barrel would be about half. That would seem to make my point until I figured that the difference in mass is about .15 grains for a .22 cal barrel 24 inches long.
So, this will make a small difference, but we'd be talking maybe 20 fps, and I'm just speculating at that.
As for the original post, something is wrong. You either got the wrong bullet weight, or a bad chronograph.