I've been a gap shooter for the last several years. I've been hunting with a short recurve for the last 2 years since it's lighter & I can shoot while seated right on the ground. I haven't liked the larger gaps I've had -- about 18" or so. My 62" recurve shoots the same arrows with a 8-10" gap but is heavier to tote around and has to be aggressively canted when I'm sitting a** to the grass, which is how I often hunt. So I put some time into trying to figure out how to shrink the gaps on this short little bow & make less guess-work in the field.
While playing around with a few different arrow lengths & weights, I noticed that they pretty much all hit the same spot out to about 20 yards. These arrows ranged from 530 - 680 grains and were about 29" - 32" in length. Spines ranged a little but all were within 10# of each other. All stacked up in roughly the same spot with no noticeable difference in gaps. By 30 yards, they show considerable differences in trajectories but only from weight -- heavier arrows drop further. But otherwise, arrow length didn't seem to matter at all for gaps.
So I took two arrows of different lengths and noticed that, from how I view them under my eye while shooting, there is barely any perceptible difference between the two. An arrow of 32" long looks about the same as one that's 29" long at that steep angle. This is shooting 3-under with a middle-finger anchor in the corner of my mouth. I suspect that somebody shooting split finger or index finger anchor would see more of a difference, though neither of those shooters would really care much about their gaps, I imagine.
So from 0-20 yards, neither the arrow's length nor its weight made much of a difference, if any at all, on my gaps. Once out to 25-30 yards, weight made a big difference. But not arrow length.
What seemed to make the most difference was simply the bow I was using. Switching to a different bow of similar draw weight showed the exact same results but with a smaller gap. The longer bow, for whatever reason, set with an almost identical nock height, shot 3 under, has half the gap distance. I've taken video of my face to see if the arrow sits higher on my face at full draw but can't figure out why it has such a smaller gap. But it does. Every time.
I'm curious what other things folks may have done to shrink their gaps. I'm also curious if anybody else has experienced similar results or if my results are just unique to me and my wonky form.