another point I forgot about an AI, and the main reason they do not show your typical pressure signs. they also remove a lot of the body tapering of the case, so the taper is not acting as a wedge during peak pressure increasing bolt thrust, this is why you gain 10 or more percent MV with 2% more capacity. which is kind of unique for rifle cartridges.
Take for example my 7mm STW It uses 17% more powder than the 7mm RM, but only gets a 14% increase in MV.
RR