Rifle bedding

Rifle bedding (also known as glass bedding) is the process of filling gaps between the action and the stock of a rifle with an epoxy based material. The bedding creates a stable and precise fit for the contact surfaces. Bedding is a technique employed in accurizing a rifle and to a lesser extent prolonging the life of the stock.

Bedding increases accuracy in part by relieving stress on the action. The rifle's action will rarely sit flush in the stock without bedding. This causes the action to flex when tightening the bolts holding the action to the stock. The flexing results in a loss of accuracy. Bedding will create a flush surface for the action and prevent flexing. Bedding also reduces movement of the action in the stock. Without bedding, the action may be more likely to shift after a shot. If the action shifts and does not return to same spot in the stock the rifle will lose the ability to maintain zero.

Bedding can help prolong the life of the stock. Repeated recoil forces can cause movement of the action in the stock. As the action moves, friction can create wear in the stock surface. Eventually the repeated wear can ruin the stock.

Several different methods of bedding can be used depending on the type of stock, desired results and level of experience of the person attempting to perform the bedding.

Methods include:

Full contact bedding of the action with the barrel floated is a very common method for long range rifles with a heavy barrel. A free-floating barrel will generally produce the greatest accuracy. However, a pressure pad under the barrel just forward of the action can sometimes improve accuracy by acting on barrel harmonics and reducing stress on the action from the weight of the barrel. Pillar bedding can be used to float the action as well as the barrel, but the process is more difficult.

Generally a slow, hard drying epoxy is used as bedding for a rifle. The epoxy should dry very hard to withstand recoil and prevent flexing of the action. The epoxy should not shrink or expand after hardening. Several epoxies are designed for outdoor use where they need to expand and contract with changes in temperature. These epoxies are not suitable for rifle bedding. Some epoxies are supplied with coloring additives to allow the epoxy color to match the stock color. Most other epoxies are only available in one or two colors. Some epoxies will come with release agent, otherwise cooking spray, car wax or shoe polish can be used instead.

Tools that may be helpful when bedding a rifle are:
Long, replacement action bolts with heads removed, modeling clay, masking tape, electrical tape, inletting tools or Dremel, sand paper, stock vise, barrel vise or suitable holding fixture, cotton swabs, rags and cleaner/degreaser.

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Wikipedia