Muzzle velocity

[shoots_5]

Can you calculate your true muzzle velocity? By that I mean, we measure the velocity with a chronograph about 10 feet in front of the muzzle, the bullet is slowing down the instant it leaves the muzzle, so is there a way to calculate what the bullet velocity is at the actual muzzle? Or is it such a slight variance to what our reading at 10 feet is that it doesn't matter?

I'm trying to get into shooting longer ranges out to 800-1000 yards and running some ballistic numbers in Sierra's program a muzzle velocity change of 15 fps makes a 1.58" difference at 800 yards so I got to wondering if my initial muzzle velocity data was in fact accurate enough?

Thanks in advance,

Tim

 

[DrMike]

The difference in velocity at even 15 feet versus the actual muzzle is negligible. It is so slight as to make no practical difference in calculations.

 

[shoots_5]

Thanks DrMike. That's what I was thinking but I wanted to make sure I wasn't missing something important!

 

[Charlie-NY]

My calculation:

I used a 180gr .308 bullet w/BC of .500, fired at 3,000 ft/sec. The velocity loss in the first 10 yards is 19 ft/sec. At 15 ft from the muzzle you would see about half of that or a 9 ft/sec drop.

 

[Ridge_Runner]

chrony your load from 15 ft
put the numbers into your ballistic program, set the range increments at 5 yard intervals, watch your 5 yard velocity, bump your MV up till the 5 yard velocity matches what your chrony said.

Yes it makes a difference, 75 fps will make an over 1 MOA shift at 800 yards from a 338 wm firing a 250 gr smk.

Thats how to be sucessful at long range shooting, keep everything in your control as close to perfect as possible.
RR