I got a concave nub/spacer for my hop up unit. I was looking at pictures of them in action and how they curve the bucking to stabilize spin and whatnot. But when I look at my bucking it has a small protrusion that enters the barrel to touch the bb, instead of just being flat.
It looks something like this:
-\____/--------\
-----------------/
Instead of this:
-----------------\
-----------------/
Is that normal? Is the protrusion thing going to be too difficult to bend and negate the advantages of the concave nub? I'm thinking it might be intended to get stronger spin on the bb, but I've never handled any buckings besides my own.