Did anyone else catch the latest installment of the Hornady Podcast on YoutTube about Barrel Cleaning? It really had as much to do with showing some barrel life (data?) estimates for their lab test barrels/guns as it did about cleaning. They even differentiate between what was verbally described as Hot pressure versus Medium pressures, and also 556 separated from 223.
They have a big screen up during the talk where you can see a variety of cartridges showing their estimated shot counts to cleaning and to the point of the OPs issue, the bbl life.
You end up having to listen to the whole thing to glean some idea of exactly what was used for the criteria, and it is still not very clear, but in general they show a low, average, and high value for cleaning interval and barrel life. At 07:34, they stated that the barrel life shown was a "general changes of P-V and dispersion, kind of a blend".... How exactly this was done with their lab data isn't shown.
In any case, I'll link the episode it for what it is worth and warn you it is 72 minutes long in total.
It would certainly be worthy of a technical publication of the whole show in my opinion, since few outfits have the opportunity to burn up so many different bbls in such a variety of calibers, bullets, and powders, as the folks who sell bullets and publish load books.
Here are some screenshots of the 223 and 556 parts. Red was their "high pressure" and yellow was their medium pressure. If we combine 223 and 556 for best/worst estimates, they show from 6700 to 3800 rounds.
I have killed Service Rifle barrels using 77 and 80 SMK with both RE15 and Varget in less rounds, but I will add that the first place I detect the end of life is at the 300 rapids.
My theory is the heat from the cadence of two rapid strings at the sitting and prone stages contributes to lower shot count than if that same shot count were allowed to run slower and cool off.
A bbl used for rapids practice and club matches will still shoot at 600 when showing signs of opening up at 300, YMMV
Merry Christmas and Happy New Year!