I'm going to be mounting a front and rear side sling system on my 870. I don't have them yet but I want to familiarize myself with this before I get the parts. I removed the recoil pad from the butt and started unscrewing the large bolt inside the butt holding it to the receiver. It wouldn't unscrew all the way, as in it didn't actually come out of the butt. It loosened to a point and that was it. Is the butt now supposed to slide off the receiver? Because it wouldn't, I tried twisting a bit, no joy. Any help/suggestions would be appreciated. I tried a bit of WD40 on the bolt but no luck. If I try loosening it more it goes stiff.