Recently my friend's Double Eagle AX-15 arrived which I helped him pick out, and while adding a Maple Leaf 2021 80° bucking to it, I noticed this really odd feature that I will start to experiment with, which is this odd groove below the hop window.
I recall that the Poseidon something or other, a TNT😬 barrel, an Italian barrel, maybe an EdGi barrel, and a $40 gimmicky 3D printed barrel lap thing from HS5 back in the day, all of which claimed better accuracy.
Now I don't doubt that this could boost accuracy as I have been learning that BB placement is EXTREMELY important for maximum performance, but all of these systems claim to achieve the same thing, but with different methods.
For example, the Poseidon has a full length groove on the bottom of the barrel, the TNT had a nub, and a different one with two nubs side by side, and the Italian barrel and HS5 shit had three full length grooves, which HS5 claimed the top two to add backspin. I don't doubt the backspin thing, but that's sort of a dumb thing to say as that's also what an LRB
AND a hop do, both of which don't tank your gas efficiency or trigger response/bolt pull. Also, the HS5 shit was said to work with the two of these three grooves on the bottom and the single on the top and the other way around, while the Italian one had the two on the bottom, not the other way around you'd expect.
But anyways, here's pictures of the thing, these were difficult to take with my phone since macros are hard.
One more thing, this barrel is REALLY DAMN NICE, like really nice. The window doesn't impress me, neither do the grooves(grooves are grooves are grooves are grooves though), and I'm not sure how on spec the OD are, or what ID is, but the bore is really damn good. Like, with a tissue and fine metal polish it would essentially be perfect.
I will try and get this gun to a decent level without doing anything to the barrel, and I will then use it as a test gun as well as compare lapping on it since the barrel seems like a Prometheus BC Bright or an EdGi, almost no improvement from lapping.
The groove is not centered if you're using the bottom alignment groove as a guide point, or the window isn't centered, or the bottom groove isn't centered, but this is obviously not 100% legit. The groove is also not straight, it seems to hook to the left, as it was likely done by an intoxicated Chinese sweatshop ape with a Dremel from Wish.
Note the deformed edges where it looks like where the BB goes, I'm not sure if this is from BBs deforming this, or if it was purposeful. It does have about 3 mags through it in this picture though, so maybe 450 rounds.