Quick load request

[briar]

Hi guys, am trying to work up a load for a 7x64 with 168gr Bergers (bc of 0.604). 54.5gr of N165 produced a three shot "group" of less than 15 mm measured outside to outside with initial load development.

What kind of muzzle velocity should I be expecting with the above load?

Barrel length is 58cm and primers are Federal, coal to ogive 2.856" to fit the mag.

From the Vihtavouri website a velocity of around 800 m/s may be expected, but when I shot over a Steinert chronograph the above load only achieved 670 to 677 m/s.

I presume the disparity is me being a muppet when setting up the chrono?

 

Thank you

Briar