N/A Springers and how far above Sea level you are….

[BABz58]

So I bought my HW95n from AoA in AZ.
AZ IS 4100ft above sea level
And where im
At in Iowa we are at 1100ft above sea level.

Is there a chart to determine the difference in power output based on Elevation.

AoA cronied it at 750fps at their 4100ft
How much more can I expect at 1100 ft?

I will chrony it here one day when I have time.

 

[Bedrock Bob]

Phoenix is barely 1100 feet. Just about exactly your elevation.

 

[EMrider]

I'm sure that this will vary depending on the gun, caliber and the tune. That said, I frequently move between two locations that differ 4300 feel in elevation.

My guns (hw50s, R7 and pro sport, all .177) consistently differ about 0.8-1.0fpe between those two locations, with the lower power obviously being at higher altitude.

R

 

[BABz58]

As info. I found something that estimates 3% loss in FPS for every 1000ft of elevation.

Not sure on the accuracy of that.

 

[Bedrock Bob]

It's about density altitude. Not feet above sea level. Pilots use it to determine the performance of their airplane. It's the FAS but it also takes into consideration Temps and humidity.

So the density altitude calculation is dependant on other factors besides actual altitude. And from what I can gather Temps and humidity can completely negate the difference in actual altitude.

I've read anything from 2.1-3% loss for every 1k feet. That may be a good generalization. But conditions could cause that number to vary greatly at any altitude.

 

[BABz58]

It's about density altitude. Not feet above sea level. Pilots use it to determine the performance of their airplane. It's the FAS but it also takes into consideration Temps and humidity.

So the density altitude calculation is dependant on other factors besides actual altitude. And from what I can gather Temps and humidity can completely negate the difference in actual altitude.

I've read anything from 2.1-3% loss for every 1k feet. That may be a good generalization. But conditions could cause that number to vary greatly at any altitude.

Great info yet again Bob

 

[Bedrock Bob]

Great info yet again Bob

Anything i think i know about it is from reading the old threads on this forum. I'm just regurgitating stuff I've been absorbing here the past couple months.

Altitude and atmospheric conditions are a big deal where I shoot. I'm on a quest up the nearest mountain to get some hard data very soon.

 

[Mycapt65]

Huh. I didn't know AOA was that much above sea level. That explains a lot. A 22 HW50 someone had them send me was IIRC almost 2fpe lower in AZ than here in AR.

 

[bustachip]

600' here.

 

[jarmstrong]

Sky Harbor elevation

Elevation AMSL	348 m / 1,135 ft

Phoenix Sky Harbor International Airport

 

[Bedrock Bob]

A few years back I decided to buy a springer. I lived outside of Santa Fe about 9000 fas. I was told by an experienced airgunner to abandon the idea because of poor performance. He said get a PCP for altitude. I decided to buy a compound bow instead.

Now I'm down in the Rio Grande Valley at its lowest point. About 4000 fas. Springers work fine but shoot slower than expected. By about 10% as close as I can estimate. I'm struggling to get 650 fps. from my HW95 in ideal conditions.

AoA chronographed the gun with new seals and springs at 685 fps @ 1100 fas. You would expect a little better than that after things broke in. I got 650 fps. when I received the rifle and it has steadily declined from that.

So the best comparison I have is 685 @ 1100 fas vs. 650 @ 4000 fas or a loss of 35 fps in 3900 feet. That's about 3-4 days apart using the same rifle at 2 different altitudes.

It was 105 in Phoenix (1000 fas) when they did the test. The Rh was about 24% that day. It was 98 in Las Cruces (4000 fas) with an Rh of 7 when I chronographed the rifle a couple days later.

 

[KWK]

I love Sea Level
Some are former Allman Bros. members

 

[Bedrock Bob]

I love Sea Level
Some are former Allman Bros. members

That's some funky jazzy music that performs to the full potential of the powerplant. I like it!

I wonder if they loose velocity when performing in Santa Fe?

 

[BurneyCA Dennis]

I’m wondering if the two squirrels I shot in the head at 3500 feet would be any more dead if I shot them at 1100 feet elevation.

 

[Bedrock Bob]

I’m wondering if the two squirrels I shot in the head at 3500 feet would be any more dead if I shot them at 1100 feet elevation.

Unfortunately no. They would not be more dead.

But... if you missed them 1/2" high at 1100 feet because your dope was developed at 3500 they would certainly be less dead.

Generally speaking the squirrels you hit will tend to be more dead than the ones you miss. You'll hit a lot more if you know your trajectory and how altitude affects it.

The "dead" part stays the same at any altitude. It's the "hit" part that's different.