I need to reach out to JES and see what he says about the 400.
I’d imagine he’d have to set it back a thread to make it correct?
Maybe not Big B, rent and have sent to JES that 400 [Petrov] Whelen reamer, look on Quality Cartridge's website for cylindrical brass, CH4D for dies, slowly neck down to get a firm crush fit on bolt closing, trim to 2.490 then fireform, easy as pie Sir.
As Riflecrank said, my fireform loads were/are accurate enough to hunt Africa, iirc longest shot on 2015 Safari was an Impala Ram dead in the chest at 200 yards off sticks with 400gr Woodleigh Weldcore, bullet exited left of nutsack, he never moved, no need wasting the powder and lead.
