How do I work out my fps at 100 yards, using my information from 1,000 yards?

[pengo]

As my chronograph isn't working, I want to find out my FPS at 100 yards, using the speed info I have from 1,000 yards?

I was using a Berger 130gn VLD bullet in my 6.5x47 rifle, which achieved an average of 1,510fps @ 1,000 yards, according to the electronic target readout.

Is there a formula I can use, or someone who can tell me the answer, so I can input it into my iStrelok app, to be used for other distances?

Here's hoping.

Cheers. Paul

[The Gun Pimp]

Working back from your terminal vel. at 1000 yds my ballistic app gives a velocity of 2801 fps at 100 yds and a muzzle velocity of 2976 fps - which sounds about right Matey.

[pengo]

8 minutes ago, The Gun Pimp said:

Working back from your terminal vel. at 1000 yds my ballistic app gives a velocity of 2801 fps at 100 yds and a muzzle velocity of 2976 fps - which sounds about right Matey.

Thanks Vince.

I'll get that added to my iStrelok app, ready for the next comp.

PS. I've sorted out the 100 yard zero and zero stop issue today, so all good to go again.

 

[The Gun Pimp]

Hey - you beat Darrel so a good day.........

[pengo]

10 hours ago, The Gun Pimp said:

Hey - you beat Darrel so a good day.........

Oh yeh. I'd forgotten about that...LOL