I'm not sure of the diameter inside the green circle, but if you are holding around 1MOA (1" group at 100 yards) you are shooting at a match grade level. Sure, you can d!ck with your standard deviation until you are blue in the face, and it still comes down to how you can read the wind, etc. The gun is good, but the shooter is still the king of the shot.
As evidenced by
my entry into the COVID Shots challenge yesterday, I have a tendency to "blow through" my shots pretty fast. This is good when you have consistent wind, but my winds were all over the place for that challenge as we had some weather coming in. I got in about 20 minutes before it started raining hard.
To determine if it was the pellets or the gun, you can first start with a chronograph, but you really won't know unless you sort some to find out. If you are getting, say, three fliers per 40 shots, just sort 40 pellets. Keep the chronograph on there, but only shoot those pellets. If you are still seeing the same ratio of fliers, it's the gun. If the fliers go away, it's the pellets. You only have to sort 40 pellets to find out. If it is the gun, that is great as on an FX as it probably means that you just need to fine tune the valve to dial it in.
Anyway, I hope that this helps. Shoot straight...