I shoot a Switchback with Goldtip carbons, I think they are the hunter series with the green label. I had a bunch of XX78 2413s from a previous bow so I cleaned those up just to have and shoot on occassion. The carbons are longer by a couple inches, both have 100 grain heads and 4" vanes. I have weighed them and the carbons are in the high 300s (from memory so I think) and the XX78s are just shy of 500 grains, so roughly 100 grains more. Now to the point of my question.

I was at the range yesterday and shot at 20, 30, and 40 yards. The carbons and aluminums had the same point of impact. Bullseyes at all yardages, regardless of which arrow I used. This seems unusual but very nice, like having a rifle that shoots solids and softs to the same poi. How uncommon is this? I can understand that a heavier object will have more energy/momentum which will translate to better ballistics downrange. But a 100 grain weight difference and the same point of impact? Has anyone else experienced this? Thanks.

Highly unusual, I think, to get matched POI at all three ranges with that big of a weight difference.

I kinda thought so. What I would really like to know is how this is even possible. Maybe I should try shooting at 15 yards, perhaps out of the gate at 10-15 it is different.