Range Report Ballistic help

[clayne_b]

If anyone is board and wouldn't mind running some numbers for me to check and make sure My numbers are right.

I am tying to figure out the muzzle velocity



.308 168 SMK with a BC of .462?

100 yard zero

Scope height 1.90

altitude 4600

Temp 55

Pressure 30.28

Humidity 38


Shot 510 yards and had to dial 3.1 mil.



I came up with 2576 FPS

Any help is greatly appreciated

 

[Joop]

I ran it in JBM. Hopefully, I have all the numbers right. For a velocity of 2576, I show a correction of 3.5 mils. To get to 3.1, I had to go to 2700 fps.

ETA: What's your powder charge and barrel length?

 

[roggom]

I got the same 3.5 mil in G7 software @ 510 Y with that data, but to get 3.1, had to increase velocity to 2775.

 

[clayne_b]

26 inch barrel, Factory Remington 700 SPS Varmint
43.5 Varget
Fed brass
CCI 200 primer
OAL 2 and 7/8ths of an inch

 

[Joop]

I would expect a little more velocity than 2576 out of that load, especially with a 26" barrel.

I got the same 3.5 mil in G7 software @ 510 Y with that data, but to get 3.1, had to increase velocity to 2775.

I ran a G1, so that could be the difference and I think we're on the right track.

EDIT: Ah, "G7 Software". Now I got it. :facepalm:

 

[clayne_b]

Shot them over a chronograph 2625 FPS

 

[Joop]

Is this on paper, steel, or...? Did your POI match POA? Any incline/decline?

When I run 2625 in JBM, I get 3.4 mils.

 

[clayne_b]

Steel, after i input the numbers in to my phone, I shot 250 and 450 and it was right on.

 

[roggom]

Well if you are clocking 2625fps then you can change BC until your trajectory matches. Shooting at 55 degrees, the DA should not really change, well at least not .4 mils worth. 168 over 43.5 2.870, could be a bit slow, but I was pushing 168 amax 2620 with 44.5 2.825 out of a 20". I would think you would be closer to 2700 with the extra 6" ob bbl.

 

[clayne_b]

They are 2.87 OAL