There are lots of good responses in this thread (and some which I think are off base). Since a comment of mine inspired this thread I snagged my response to the question from over there to help show where I was coming from.
"460, You are correct that the individual firearm is critical to accuracy. With a given firearm their will be some specific loads that shine.When speaking of "inherent" accuracy of cartridges/chamberings we are talking about planned design criteria(such as the PPC rounds) or happy coincidences that make some cartridges "easier" to achieve a high degree of accuracy. This doesn't mean that a particular firearm and load of a not particularly"inherently accurate" cartridge can't trounce lots of the "inherently accurate" chambered guns. However some chamberings are known to be very non-critical regarding bullet weights and powder charges to achieve accuracy. Other cartridges have a deserved reputation of being difficult or even exasperating. For instance the 32-20 that I mentioned-There are guys who have shot beautiful tight groups with a 32-20 revolver...but the same gun, same brass, same bullet weight and a different powder loaded to achieve similar velocity scatters shots all over the paper. OTOH most decent .38 specials will shoot reasonably well with any load and spectacularly well with some. It is an easier/more inherently accurate cartridge. The 9x19 is a tremendously efficient cartridge (small charges for top performance) and is not problematic in achieving adequate accuracy for most purposes.....but it is harder to get it to shoot all the bullets through the same hole than a .38 special or a .45 ACP."
"460, You are correct that the individual firearm is critical to accuracy. With a given firearm their will be some specific loads that shine.When speaking of "inherent" accuracy of cartridges/chamberings we are talking about planned design criteria(such as the PPC rounds) or happy coincidences that make some cartridges "easier" to achieve a high degree of accuracy. This doesn't mean that a particular firearm and load of a not particularly"inherently accurate" cartridge can't trounce lots of the "inherently accurate" chambered guns. However some chamberings are known to be very non-critical regarding bullet weights and powder charges to achieve accuracy. Other cartridges have a deserved reputation of being difficult or even exasperating. For instance the 32-20 that I mentioned-There are guys who have shot beautiful tight groups with a 32-20 revolver...but the same gun, same brass, same bullet weight and a different powder loaded to achieve similar velocity scatters shots all over the paper. OTOH most decent .38 specials will shoot reasonably well with any load and spectacularly well with some. It is an easier/more inherently accurate cartridge. The 9x19 is a tremendously efficient cartridge (small charges for top performance) and is not problematic in achieving adequate accuracy for most purposes.....but it is harder to get it to shoot all the bullets through the same hole than a .38 special or a .45 ACP."