I've read that certain cartidges have limited barrel life because they have too large of a case necked down to too small of a caliber, producing too big of an explosion going through too small of a hole. For example, the 6mm/06 is said to have a much shorter barrel life than the .30/06. However, I've been thinking that maybe the problem is that the case is actually too small and things could be solved by using an even larger case. I've read that excessive chamber pressure and the corresponding temperature increase is the main culprit in limiting barrel life. Considering this, I don't understand why the problem couldn't be solved with larger cases. For example, it is a well known fact that the .30/06 can produce the same muzzle veloicty as a .308 Winchester with lower chamber pressures when underloaded. Could a .50 BMG be necked down to .30 caliber and produce the SAME VELOCITIES (using only an extremely small percentage of the useable case capacity when loading, of course) with even lower chamber pressures? You simply load the new .30/.50 BMG cartridge with WAY less than it's full load and have a little bit of powder flopping around in a huge, cavernous case. What if someone necked a .50 BMG cartidge down to 6mm caliber and only used a small amount of the useable case capacity so that chamber pressure would not be as excessive, yet high velocities could be reached? Imagine someone likes the 6mm/06, except wants a longer barrel life. He simply necks a .50 BMG cartidge down to 6mm and launches 70 grain bullets at varmints all day long at the SAME VELOCITY (i.e. weak, weak, weak loads) he could with a 6mm/06 with lower chamber pressure (and correspondingly lower temperature) and enjoys longer barrel life. The .50 BMG cartidge could be the foundation of everything from .17 to .50 cartidges.