There are certain brands of ammo where the pressure from a shot seems to deform the brass, making the cartridge very difficult to eject.

I'm using (4) 7mm Rem Mag rifles. Usually if one rifle has difficulty ejecting the casing then the other rifles do also, at least to some degree.

There are certain brands where I never have a problem and others are consistently bad.

I suspect I already know the answer to this, but do certain mfgrs just use softer, cheaper casings?