Benelli SteadyGrip installation.. problems

[TNReb]

I bought a SteadyGrip stock for an SBE II off Ebay.  It's supposed to be new.

I removed the recoil pad. 

On my standard SBE II stock, there is a hole all the way through the stock where the recoil spring assembly from the receiver extends through. 

In this steady grip stock, there is no such hole.  The hole is plugged up.  There appears to be a bolt about 3" long already in there with some shims and plates.  I can't wiggle it loose.  I can't seem to push it out one way or another.  I have no clue what the heck is in there and how to get it out. 

Or did the guy sell me the wrong stock?

[TNReb]

[allaboutshooting]

That looks like the recoil spring assembly. I can't see the picture very well but you should be able to unscrew it.

Thanks,
Clark

[TNReb]

That looks like the recoil spring assembly. I can't see the picture very well but you should be able to unscrew it.

Thanks,
Clark

Kind of what I thought.. but I can't get it to budge with just my fingers.  I'm hesitant to take pliers to it because I don't want to strip the threads in case it's actually needed for something.

[TNReb]

Looks like this stock is for an M4.  Go figure.