GSG-5 PK - does a sling make it an SBR?

[BigDaddyCan2]

I don't know about the sling, but do not even have a stock in the same vicinity of the gun unless you have the SBR paperwork, they will nail you to the wall. Vertical foregrips are also a no-no.

I hear that, not gonna happen here.

Once a paratrooper, always a paratrooper, just remember, feet and knees together and make sure you hit all five points of contact, especially the fourth...............

 

[Big Bad Wolf]

I saw these at the Local gunshow this weekend... How well do those of you who have them, like them? pretty good? function well? feeds anything or are they a bit picky on what they digest? Really looks kinda cool to have one...