Derek, 308 Sako,
As suggested, went out to check the chrono’s calibration today. Not going for statistical validity here, trying to get a feel for what's going on:
2 rounds of Lapua factory averaged 2689fps. Not bad for a claimed MV of 2690!!
…….Chrono calibration confirmed.
This was the set-up, chrono 10ft from muzzle. It's a CED Millenium chrono:
My pet load clocked 2722fps (the cases I used yesterday were ‘spares’ rather than my super-duper prepped cases):
Despite confiming the 2722fps actual MV, the data input required to model the ‘observed’ trajectory is as follows: [img]/ubbthreads/images/graemlins/confused.gif[/img]
MV (fps) 2580
Bullet Wt (Gn) 165
Start Range (m) 0m 0 Yds
Increment (m) 25m 27.34 Yds
Impact Ht (cm) 1cm 0.3937 in
Zero Range (m) 100m 109.36 Yds
Pressure (mbar) 1000
Scope Ht. (cm) 4.9cm 1.91 in
MOA value @ 100 yds 1.047in
Retard. Coeff. rate 0.5
Break Velocity (fps) 1300
Ammo/Rifle Description AW: 165 BT, 45 gr V140, 56.7mm
Laser Range: 101 Angle of Sight: 0
Wind Speed: 15 Altitude (m): 115 Pressure (mbar) 1000
Wind Dn: 3 Temp: 11
By the way, 46grs of v140 pushed it up to 2800fps. Reckon that’ll be my Scotland load [img]/ubbthreads/images/graemlins/smile.gif[/img] …but what MV will I input to model it???