Elevation Effect

[Tim99]

I'm new at air rifles and was looking getting a brake barrel. I have read a lot online and watched a bunch of video trying to get all the information I can. I am looking shooting prairie dogs and rabbits. My question is the speed of the rifle. I live at 6000 feet. If one rifle is rated at 1200FPS and another rifle at 900FPS. If I shot the 1200FPS rifle at 6000 feet elevation and it produces a speed of 750FPS could I assume the 900FPS rifle would only shoot at 750FPS as well?

Tim

 

[bandg]

Seems there are way too many variables in this scenario to work with. And you will probably discover that the "ratings" are vague guidelines at best. Rated with what pellet by each manufacturer? My suggestion would be to start with the maximum distance you need to shoot and your budget, then ask questions about specific rifle models that you have interest in. You will hear many opinions of what is "best" once you identify some basic parameters such as budget and shooting distance. JMO.

 

[Glem.Chally]

Take break barrel specs with a grain of salt unless they're British or German. Cheap ones advertise the speed using tin pellets to look impressive. A "1200 fps" walmart gun will probably be around 800 in the real world using lead pellets.

 

[biohazardman]

Most manufacturers test guns with very light alloy or the lightest lead pellet they can find. Most shooters will warn you not to shoot the lightest pellet you can find as you will do damage to the gun. Also light pellets are seldom accurate enough to hunt with. So, you need to find a gun made by a reputable company that states what the weight is on the pellet they use in the test. Or find someone who has some real world data on a specific gun. Likely you will be limited with a decent brake barrel to the range you can hold a one inch group so probly for most at the best 40-50 yards once you find the right pellet and practice enough. Check out the springer section of the forum for some good info.

On your assumption if the 1200fps gun shoots 750fps then the 900fps gun is not likely going to shoot the same speed more like 450fps. But as has been stated for the most part don't trust the numbers.

 

[Hutch3030]

U don’t want to shoot any faster than 850-950 FPS for pellet stabilization reasons. Also heavier pellets have better ballistic coefficient 

 

[JimNM]

FWIW, at the same temp and humidity, you will see about 3% difference in air density per 1000 feet above sea level. 6000 feet is 18% reduction in number of air molecules that are present in the compression chamber at the time of firing. Less air to compress = less energy transferred to the pellet.