Rem 11-87 loose stock!

[BigWay]

I bought a Remington 11-87 super mag (full camo) last year brand new. I picked it up the other day and noticed the stock was loose. I can twist it back and forth. I took off the butt plate to tighten it up, but i can't seem to figure out how to get it tight. There seems to be a hollowed out nut with a pin through it. Does anyone know how to tighen these up? I don't really want to take it back where I got it, they would probably have it to long, and I need it to throw buckshot for the next three weeks.

[Big Guy01]

I have a regular 1187. When you take the but pad off there is a big flat head bolt recessed in the butt of the stock. Just tighten it. If it won't tighten up remove it , it could be stripped and need to be replaced.