eldeguello

Quite simple. A custom gunmaker can charge big bucks to inlet a barrelled action into a piece of wood so closely that you'd think the tree grew around the metal. Factory stocks can never fit like this, but to shoot their best, most guns need to have their stocks fitted pretty closely-usually closer than the factories can afford to do and still sell their guns at a price you and I could afford! The use of a fiberglass-filled epoxy-resin compound between the wood and metal (or synthetic stock and the metal, such as yours) provides a reasonably economic way to make the stock and barrelled action fit closely.

To do this, some of the stock material is removed from the receiver recess and the barrel channel, and replaced with this epoxy resin compound while the stuff is still pliable, then it is allowed to set up hard. When done, the stock and barrelled action fit extremely closely, and are bedded in a material that's stronger than either the original wood or composition material of the stock.

This is "glass bedding". Several companies make this stuff, such as Brownell's "ACCRAGLAS" and "ACCRAGLAS GEL" I have used both of these products, and they are great!