high and low pressure affects on pcp power

[choppork]

another strange one as any one else noticed a change in power in there 12 fpe pcp , when testing power with a chronograph ,when there is a high pressure over the country , your pcp will be slightly lower on power , from that what you would get on a low pressure on a chronograph usually up to 20 fps ,your thoughts please

[Murphy]

Not sure I understand your question but are you talking about the power curve every PCP has?

[zephyr]

Are you referring to variation atmospheric barometric pressure?

[Antoni]

The maximum difference in barometric pressure is very roughly 'less than 0.1 bar' or 1 psi. Compare that to the 100+ bar or 1500+ psi propelling the pellet.

Could it be that high pressure days in summer are usually warmer so the outdoor temperature of the gun affects the doin's in the gun? Having said that, in winter high presure days can be cooler.

The air will be denser on a high pressure day and could slow the pellet down over distance, but it isn't usually very far from the muzzle to the chrono...

So why am I wasting your time writing this? Because it's 4 in the morning, I'm bored and it's an off the wall question.

I do remember setting up the tickover speed on my fuel injected XR3i and wondering why it drifted from week to week. Thought at the time that it could be exactly what choppork is talking about.

[Tricky-Ricky]

Sounds like he is describing the power curve variations from an unregulated PCP to me.

[Antoni]

Reminds me of the comprehension tests we had to do at school.

[Rich]

A typical 'high" over this country would have a barometric pressure around 1030 millibars, where the sea level "standard" is variously 1000 to 1013.2 millibars. A deep low pressure would be something like 960 millibars and there would be pretty strong winds associated with that so any marginal change in rifle power is probably not relevant.

However, the air density will vary by about 5 percent between these two extremes, and as the deceleration of the pellet is dependent on the air density there would be a change in trajectory, but I doubt if you would see a change in indicated power with a chrono placed near the muzzle.