4000+ fps

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.
 
I once had my chrono tip over on the tripod because of wind and when it fell it pushed the sky screens closer together which caused it to read about 200 fps too fast.
 
Slight pressure signs in my 223AI with a 24" barrel and 50 gr ballistic tips have been reading between 3850 and 3875 on average, behind 26.8 grains of reloader 10x. Same load in a different rifle clocks at 3650 average. My rifle is a cooper with a lilja barrel put together by Neil Jones, it shoots awesome groups.
 
I shoot a number of calibers over my 20 yrd range in the basement. Amazing how guns configured the same (caliber, barrel length) will print substantially different velocities. 45 ACP 5" inch can differ by as much as 200 FPS (Springfield and Dan Wesson at 1000 fps with 185grn XTPs vs 800 fps with a duel stack para). I don't get quite the difference in .223 and 22-250 with the same barrel length. As to different chronys, I get that too. Mine may be off but I have to guess it is off by the same margin, regardless of what bullet passes through the screens.

As to altitide, I understand the aviation part with air speed and fuel suck. The air is thinner and provides less resistance. It takes less fuel to achieve the same air speed. However, there is a lot more involved in fuel consumption at altitude than simply generating air speed. This not being an aviation forum I will not comment further unless some one shows an interest. However, it is a very interesting question, especially if you are the one buying the AV gas at $6.00 bucks a gallon.
 
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