Current 6mm Grendel barrel makers: BHW, McGowen and who else?

[Kilco]

I wonder if the number of grooves, hence deformation on the bearing surface of the projectile has any long term effects on the ballistics of that projectile...

No idea... just thinking out loud..

And for a wildcat without SAAMI recognition like the 6mm Grendels, you would have some wiggle room regarding total groove area contacting the projectile, or "X" as BFT put it..