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I once read (but can't find again) that the total heat content of the powder in a 223 isn't enough to damage a barrel.
The theory was that it isn't the velocity of the bullet or the pressure of the firing that erodes barrel steel, but the total heat content of the burned gas. As the BTU content of smokeless powder is finite and known, there is a charge weight minimum that can "burn" barrel steel. That minimum charge weight is (if I recall correctly) somewhere near 35.0 grains. Plus or minus a bit, depending on powder type.
Cartridges with less than 35 grains charge weight therefore cannot "burn" or erode barrel steel. In rounds that small, it's physical wear from friction - or chemical wear from corrosion - that "wear out" barrels.
The .223 falls in that range of rounds that hold less than the magic 35 grains. The .22-250 holds more. As many have noticed, a 223 will last darn near forever, while a 22-250 wears out after several thousand shots.
Maybe there's something to that theory.
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