FPS FPE and distance question

[WN0912]

Hi.

I've got a Benjamin Maximus PCP rifle 22 caliber that I've measure FPS (Feet per second) with Chronograph and then calculated the FPE (Foot Pound of Energy).

My question is, how do I determine the degradation or loss of FPS and FPE as related to distance?

For example, if the FPE is calculated to be 20 with the chronograph at the rifle, what is it at, let's say 30 yards?



Thanks!

 

[Longfellow]

Are you familiar with Chairgun software?

I just joined so I haven't memorized all of the rules yet. I'm not sure if posting links for it is acceptable here or not. The manufacturer/creator is Hawke. That will help when you look it up.

It's easy to use. Plug in the pellet you're using. The velocity and BC of the pellet. The range you want to sight in your Maximus at for that particular pellet and it will give you everything you're looking for.

For example: Lets say I want to hunt coons and I know the minimum fpe for reliable penetration of their skull to make a brain shot is 10 fpe. Lets say I'm using a .22 Crosman Summit Ranger NP2 using AA 16 gr pellets at an average velocity of 730 fps. Since the limiting factor will always be how accurate I am w/ that particular rifle and pellet, lets say I know I can shoot <1 inch groups at 20 yards w/ that particular pellet from my SR. That will be my sight in range.

Chairgun will then show you a graph of the trajectory and a table with all of the pertinent data: in this case, I will have 673.7 fps and 16.12 fpe at 20 yards. 

 

[elh0102]

Here is a link to the trajectory chart on the American Airguns site. It gives fpe at any increment you enter. This chart is old, and I'm not familiar with the source program, but fpe is a simple calculation, so I assume it is reasonably accurate.

http://americanairguns.net/trajectory.php

 

[B7B]

Or you can borrow or buy a cronograph with a big measurement surface (like the Caldwell Ballistic Precision Chronograph) that I use for arrows, and put it close to the target. U can have the speed at any distance.

 

[elh0102]

I think he's interested in the relationship of velocity and energy, as they change with distance. Since energy varies with the square of velocity, it's not a linear relationship. Velocity has the larger influence, but I'm not sure that translates in the same manner when considering field performance.

 

[WN0912]

americanairgun chart is perfect for what I'm looking for.

Looks like the results show that although the FPE drops at further distances (as expected), it doesn't drop all that much.



Thanks everyone.

 

[B]

Didn’t check americanairgun chart but this is what StrelokPro shows with 16 gr. pellet

B

 

[TeOh1776]

You can use 2 Chronographs. so you get the starting speed and impact speed then you convert it to FPE and you'll find your loss over the distance. 

 

[elh0102]

You can use 2 Chronographs. so you get the starting speed and impact speed then you convert it to FPE and you'll find your loss over the distance.

Last time I tried that, I shot one of my chronographs, easier to look at the chart, and considerably less expensive.