Re: 123 Amax in 6.5mm
Have not tried the Lapua. I've fired about 400 of them through my factory LR-260.
They have a real BC pretty close to what Hornady lists, I've been using 0.500 G1 in my calculator and it's within 1 MOA at 1000yd
They're impossible to find right now (along with most Hornady bullets) but they are very consistent and do a great job on paper and game alike.
Printed groups are not something I shoot much of, but both LR260 uppers that I've worked with (mine and a buddy's) shot this bullet well inside 3/4" at 100yd over and over again.
My load data is below, it's warm for a bolt action and hot for a gas gun. As the adage goes "start low and work up"
Win 243 brass (sized up and prepped)
CCI LR #200 Primer
45.4gr IMR4350
Seat to 2.800 +/- 0.003" overall
Base to Ogive = 2.200"
Feeds from the DPMS mags and runs 2940fps from a 24" barrel.