Re: .300 Lapua Mag.
For the life of me I cannot figure out why someone will build a custom gun with $500 barrel (blank and chambering) talk about pennies on brass.
Brass is the cheapest component in a custom system. Do not be stupid and scrimp here.
Buy the best brass that is available. 100 pieces of 338 Lapua is only $130 from Sinclair and that is full retail. It can be found cheaper. 100 pieces of lapua will outlast two barrels.
I am tuning a 30 hart (300 Weatherby improved) right now for someone now and they have Rem brass. the loads for the Rem brass are blowing primer pockets on 10-20% of the cases and that is backed down. I have wasted time, money and still going to have to order decent brass.
When you build a custom gun, brass should be part of the equation for chambering and setup. Buy either Lapua, RWS (best if you can get it) or Norma.
In my opinion, Rem brass in a custom gun is like a Yugo engine in a NASCAR body.
Well off my soap box now.