Range Report What speed are the bullets ? And why ?

[capt561921]

What speed are the bullets going and is there any reason why they would slow down.

The rifle is a 6.5x47 lapua, 25 inch barrel.

data as follows:-

Humidity = 74.2

1001 mb

Temp = 3 deg C

Wind slight R-L at 2 mph


The bullet 123 gr senar.

charge 37.5gr RL15

Zeroed at 100m and grouping 1/4 inch,

The rifle was hitting the gongs centrally at the following distances consistently

At 410m milrad 23 clicks

At 510m milrad 34 clicks

At 744m milrad 65 clicks


Interestingly when I looked at my other cards that have worked for same load in the past the data is as follows:-

Chart at 2915 fps (data taken at 15 deg C)

At 410m = 19 clicks

At 510m = 21 clicks (+1 for temp)

At 744m = 55 clicks (+2 for temp)


Chart at 2880 fps (data taken at 20 deg c)

At 410m = 21 clicks

At 510m = 31 clicks (+1 for temp)

At 744m = 58 clicks (+2 for temp



What would cause the bullets' to slow ?

Has anyone else experienced this ?


Kind Regards

 

[ksthomas]

Re: What speed are the bullets ? And why ?

You mentioned a fairly significant drop in temperature which would account for some change in velocity. Especially true in light of the fact that you're using a double-based powder, which tends to be more susceptible to such changes.

Beyond that, my guess would be a change in barometric pressure, which can account for fairly significant changes at distance. My money would be on the pressure, first and foremost.