Many 6.5 Grendel users on the 65grendel.com forum have claimed 8,000-10,000 rounds life, and as they are mostly AR shooters that's a pretty impressive figure since few people buy semi-autos to shoot deliberate slowfire. I'd assume too that most such users will have custom 'uppers' employing relatively soft steel stainless match or semi-match quality barrels, so a 6.5G Cz527, Mini Howa or Savage factory rifle ought to be better still with their very hard hammer forged chrome-moly tubes.
However, as
@gunsandgunsmithing says, a huge variable is people's definitions of acceptable precision - one person's 'shot-out' is another's 'still shooting good enough'.
I reckon that a key reason for the 6.5G's long barrel life is the 50,000 psi MAP because of the AR bolt limitation. That's aside from such a small case and relatively low powder charges of course. If you apply the barrel life Excel calculator whose link is available here:
http://bulletin.accurateshooter.com/?s=barrel+life+calculator&submit=Search
my load of 26.6gn of relatively cool burning Viht N133 shot very slowly produces a value of 8,544 expected life. Realistic? Who knows, but I'd be surprised if I have enough range hours left in my life to shoot my Howa Mini's barrel out, and I'll most likely become bored and rebarrel it as a 6ARC (or 'Ark' as in Noah's as I note it's already being pronounced including by Hornady staffers) long before it's finished. Glancing at recent threads as to what loads might be used in this cartridge, we appear to be talking similar powder weights to my 6.5 / N133 weight, but slower burners such as H4895. Rerunning the spreadsheet as 6mm, (much 'hotter' than N133) H4895, and the ARK's SAAMI 52,000 psi reduces expected barrel life down to 3,395 rounds.
The other way of looking at it is the case (water) capacity to bore area method as seen here:
http://bulletin.accurateshooter.com/?s=overbore&submit=Search
........ and comparing the pair to existing well known designs.
The 6.5G gets a ratio of 639 which is 45 below that of 222 Rem, a cartridge known for exceptional barrel life. It's 100 above that of the 30BR about which some have joked that nobody knows the barrel life because nobody has ever worn one out. Perhaps more appropriate is that it is well below those of 223 Rem and 308 Win and given the Grendel's lower pressures the little 6.5 is going to outlast this pair by a lot.
The 6PPC works out at 711, so depending on which version of 6mm is used, the value will be a bit higher for 6mmG / ARK similar to 308 Win but running at lower pressures.
Load anything hot enough with heavy bullets, demand consistent quarter-MOA precision and you'll get low barrel life. I have many 308 Win F/TR shooting friends whose barrels only last 2,000 rounds give or take 200 thanks to very high-pressure loads in strong small primer brass allied to 185-215gn bullets. I know others (although not many nowadays) who boast they've stretched their 308 stainless Palma barrels to getting on for 10,000 rounds and it's just about good enough (2-MOA targets).
