dont know the name if this part.

[DrEvil]

whats the name of the springy part that goes into the groove of the barrel? and is it adjustable?

[mrhooie]

nubbin

yes, it's adjustable, you just bend it yourself (keep the general shape the same though)

[DrEvil]

no im sorry not the nubbin. its the part in the body rail. sorry.

[Ariestsheft]

thats the twist lock assembly

[PyRo]

Twist lock assay.
It is ajustable on the bottom half of it there is a small screw, the further in that is, the tighter it will be.