Velocity calculation at given distance

[Bakerjd]

I am wondering if I can use the chrono reading from 1ft away to figure out what it would be at 10ft away. I tested two loads today but wasn't about to he 10ft behind my chrono because there were other people at the range. Hopefully someone much smarter then me can help me out. 

 

First load:

My average FPS at 1ft was 891.4 and average PF was 130.83

 

Second load:

Average FPS at 1ft was 930.3 and average PF was 136.71

 

 

[DesertTortoise]

I don't think the velocity will be different at 1 ft vs 10 feet. The difficulty is that the chrono may not be able to accurately measure at 1 ft due to gas, powder, etc interfering. 

 

[Bakerjd]

17 minutes ago, DesertTortoise said:

I don't think the velocity will be different at 1 ft vs 10 feet. The difficulty is that the chrono may not be able to accurately measure at 1 ft due to gas, powder, etc interfering. 

 

Ahh ok. I've read some places that say the bullet will actually be going faster at 10ft then it was at 1ft. 

 

Chono readings seemed to he pretty much what I expected though. 

[xrayfk05]

13 minutes ago, Bakerjd said:

Ahh ok. I've read some places that say the bullet will actually be going faster at 10ft then it was at 1ft. 

 

That's impossible, as soon as the bullet leaves the barrel the only forces acting upon it are gravity and drag.

It will be slowing down and dropping, unless fired straight up or down ofc

 

Do a search for ballistic calculator and you can easily find out for yourself, for any distance.

[Bakerjd]

55 minutes ago, xrayfk05 said:

That's impossible, as soon as the bullet leaves the barrel the only forces acting upon it are gravity and drag.

It will be slowing down and dropping, unless fired straight up or down ofc

 

Do a search for ballistic calculator and you can easily find out for yourself, for any distance.

That's what I thought.

[Farmer]

7 hours ago, Bakerjd said:

That's what I thought.

What weight bullet and type are you using. I’ll see if the calculator I have will work at that distance. Like Desert Tortoise said, being that close can give erratic results. 

[Guy Neill]

Go to the JBM website and use their ballistic calculator.

 

[Farmer]

@Bakerjd My calculator only does yards but your load that’s running 891 fps from 0 to 10 yards only loses  7 fps in 10 yards so I wouldn’t sweat it.  What’s funny is the 930 load loses 9 fps in 10 yards but that’s typical for a faster load to bleed off more speed quickly at first. 

[Bakerjd]

Thanks everyone. I ended up just splitting the difference of the 2 loads anyways and loading at 3.1gn. Bullet weight is 147gn.