No experience with the HM2 yet.  And on the HMR the estimates seem to vary significantly.  Lilja says I should expect 3K accurate shots (assuming you don't get it hot etc.).  I had "read" that someone on Rimfire Central still had good accuracy at 30K shots.  I didn't put too much stock in that estimate.  At today's ammo prices that is over $10,000 of ammo.
Before I left for my shoot, I shot a target with 6 different loads at 100m as I knew I was going to transition from the Hornady 17 gr VMAX I had been shooting in it primarily.  Round count on the barrel when I shot this target was around 4600.  I wanted to see if POI changed and what the group size was for the other ammo.
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When I finished the partial case of the Hornady, I had added 1440 shots.  So now I was just over 6K.  I went to the CCI tipped and accuracy was gone with the first shot.  I switched to my backup rifle and continued.  That night I cleaned the barrel (chemically not mechanically) and shot a test target the next morning.  5 of the 10 shots were sprayed.  So I finished the shoot with my backup rifle.  I've been cleaning the barrel for evaluation if my issue was fouling or barrel wear.  I can't use the 90 degree mirror on my borescope, so it is challenging to evaluate the condition of the barrel.  Best I can tell it just looks frosted and I don't see any firecracking.  But my view is poor at best.