You could be right. The XM8 boasts a 20,000 round minimum barrel life, however, I haven't been able to find any statistics on the C7 barrel life to compare. I know that the C7 has a longer barrel life than the original M16, as does the XM8, but I'm not sure exactly how they compare to eachother. The XM8 DOES use special alloys but once again I'm not sure which. From the reviews and releases I've read, the strength of the barrel has been improved to the extent that it's possible (although not advisable) to fire it with the barrel clogged. I know you can't do that with the C7, so I assume that a stronger barrel also translates to a longer life span, but that's just an uneducated guess.
Keep in mind that the XM8 may be based on the G36 but it's no more a G36 than a C7 is an AR15.