Flats vs Moons POI/Partial Dryfire Question

[nchunterkw]

I learned something this weekend. Last week I was shooting some Carbon Express Maxima Hunter arrows with flat nocks. These nocks were previously moon nocks and I shaved them down. The arrows came with flat nocks, but they were of a slightly larger diameter than the arrow shafts for some reason. So I was experimenting to see if there was a difference. After shooting the same arrow probably 20 times, using an FFF string I got a partial dry fire on it. I talked to Danny Miller the next day and he explained that the FFF string is a bit smaller diameter and it must have slipped under the arrow. He suggested using the moon nocks. So Saturday I tried this. I actually went a step further and changed back to an endless loop string - which is thicker - and switched to moon nocks. What was interesting to me was that my POI changed by about 2.5" higher with the moon nocks than with the flats. I verified this several times before making my scope adjustments. And after the adjustments, things shot really well - like 2" groups at 50 yards (off a rest). Anyone have any ideas why the POI was so much higher? I doubt I was getting any more energy into the arrow as I chronographed the setup with the flats (378gr total weight) at 324 fps, (shooting a Vortex) however I did not pull out the chrony on Saturday.

[awshucks]

Can't answer your questions, but your post reminded me of a lesson I learned the hard way, lol.

A couple of years ago, I had a Boo FFF that was way thinner than normal, it shot 2" high[er] at 20, so I assumed it was shooting faster.

Talked w/ Don [Boo] about it, argued some, then broke out the chrony. He was right, same fps as a regular FFF.

It was the string diameter, which I know is contrary to your experiences. I'm only guessing here, but would think it has to be the moon nocks, but sounds like you have it dialed in............

[nchunterkw]

Yeah, thinking about it some....maybe the string is sitting lower, then pushes up into the middle with the moon nock, and then drops a bit as the arrow leaves the bow and gives it a little upward kick? Interesting, but like you noted, it is shooting really well. I think I will take some calipers home and try to take some measurements to see what the difference might be. My FFF string needs re-served anyway, so I plan to have Danny put some 0.036" Angel Majesty on it - that will thicken it up a little bit.

[Dash]

I think your on the ball. I've had similar results before with moon nocks, which I put down to the fact that the string rides into the nock groove and then back down the bottom of the groove affecting the way the arrow leaves the rail. The last bit of pressure contact was not at the nock center, but forcing the lower nock down. I imagine that if the string contacted the moon nock dead center it wouldn't be an issue at all.