How does Bear creek get these 450 BM MVs?

[DartonJager]

I was rather shocked to see these factory loads in 450 Bushmaster advertising a MV of 2550 FPS

https://bearcreekballistics.com/wp-content/uploads/2020/01/bearCreekBrochure012820.pdf

Was wondering how are they able to achieve this and stay within safe pressures?
My best guess is duplex loading of powders?

 

[Dmagna]

The two the show info on are for bolt guns. I would assume the AR loading is a lot lower.

 

[cohunt]

Doesn't say what length barrel does it?