That sounds like it was the factory bedding that they put into the recoil lug mortise of all newer Winchesters. It is not great stuff but I guess it is better than having the recoil lug fit loosely into a sloppy mortise. I have the same stuff in both recoil lug mortises of my Safari Express but it shoots so well "as is" that I am not going to change it. It is also in my Featherweight. Both rifles shoot about as well as I have seen a Winchester shoot. On my rifles is much harder than rubber but it is certainly not the ideal material. Good luck with your tinkering.