There is nothing dramatically wrong with the McMillan receivers. That said, they are expensive for sure and as such, I point my customers in different directions for a custom receiver just because of cost mainly.
For any rifle based on a case up to and including the RUM class chamberings, my first choice by a LARGER margin is the Borden Timberline Magnum receiver.
For a Lapua class chambering, My first choice is the BAT HRPIC receivers. Expensive for sure but these are well worth the investment. That said, as soon as Borden starts offering a Lapua class receiver I will have two top end receivers I can recommend to my customers.
For 408 CT class chamberings, my first choice is the BAT M single shot 1.55"x8.5" round receivers.
For the BMG, I would probably lean toward the BAT but the McMillan 50 BMG receiver is pretty good, espeically if you want a repeater.
These are also the choices I use for my personal rifles so what I recommend to my customers is what I use myself.
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