You will be OK with the fired brass you already sent hornady.
I wouldn't send in a lapua too.
You will be close enough as you are really looking for a starting point for your best seating depth.

Quote Originally Posted by Ernest T View Post
I actually found Lapua SRP brass in 6.5 CM and ordered 100! Getting closer to being able to reload. Of course, now I'll have to send the Lapua brass to Hornady to make another modified case for the headspace gauge. It'll be nice to have a choice of reloading with small or large rifle primers.