Removal of recoil spring on M4

[etale]

As part of periodic cleaning, I would like to remove the recoil spring from my m4

and clean the inside of the recoil tube, plunger, and spring.

 

Using snap-ring pliers, I am able to remove the retaining clip on the stock end of the recoil tube. Underneath this is what appears to be a threaded insert that would seem to accept a straight-edge screwdriver of the appropriate size. Do I just unscrew the insert with a (rather big) screwdriver? Is there a more appropriate tool for the job? How critical is the relative position of this insert in the recoil tube? I am guessing that is correctly loads the recoil spring, and is perhaps even adjustable to compensate for wear in the recoil spring. Any ideas/ thoughts?