IMO, 3 shots does not make a group. Shoot at least 5 or more to see the true potential of the barrel/load combo. Just getting lucky that two are touching in the 3 shot group.
As I have stated in my OP, I have shot more than 3 shots following those 3 shot groups many times. The results, more often than not were pretty much the same with sometimes the flyer just being closer or farther away or even in a different direction. I have often followed up with another 3 shot group following the first 3 shot group, which would make it a 6 shot group (just at another target on the same piece of paper) Same results quite often.
Mauser9mm; If the bore is thinner at any point inside the barrel, then it would heat up faster at the thinnest part, which would shift the barrel slightly in the other direction, even mid-way.. Have that same problem throughout the barrel and it could significantly change the harmonics, not to mention the direction of the muzzle slightly. Yes, it is splitting hairs but a very possible explanation I would think.
