And the .318, 404, 375 were released sooner rather than later and so they became a little more common than the ones remaining proprietary. There wouldn't be a 7mmRem if the 275H/H used a .284 bullet

@huvius, I say the 400/360 No2 as it distinguishes it using the 400Jeffery case rather than one of the others. Also allows a little better performance and easier sourcing of brass so I could actually use it.