Glass Bedding Shotguns

The writing of this article was triggered by recent discussion posted in American Gunsmith by one of the gunsmiths. The question was how to fix repeating breakages of a shotgun inlet. In other words, when a wooden piece breaks off of the inlet, is glued back together, then breaks off again at the shot, how should you fix it? If the piece of inlet is breaking repeatedly should the stock be discarded or there is some potential?

Stock replacements are expensive, especially for the high grade shotguns, so my tendency is to do everything possible to save the broken one. Is repeating gluing of the broken piece a sufficient way of fixing the problem? Gluing is needed but probably not sufficient. Before talking about solutions, let’s look into physics of these breakages. Why does one piece but not another break off? Obviously, it is a result of some force acting upon that part of inlet which is exceeding the strength of the wood.

This force consists of two parts. One is The saved piece needs to be glued in place with minimal visibility of the edge outside. The broken piece on part A shows old glue, so this was not the first break. Part Bshows the broken piece is lost. the pure recoil—when the charge goes forward, the whole metal of the gun moves back and the receiver hits the wooden inlet. The other part is related to the motion of the shooter’s body. In particular, the torso of the right-hand shooter swings to the right or clockwise.

At that point in time, the barrel, having significant weight and inertia, resists this swing and creates pressure on the left part of inlet. This is why for right-handed shooters certain breakages are typically on the left side. For left-handed shooter, the right part of the inlet is more vulnerable. There are other forces associated with body motion which can explain cracks of the inlet in different locations.

Note that after the shot, the body moves into counter recoil with barrel inertia resisting this move as well. Altogether, the inletted part of the receiver is forced into pushes, pulls, twists, and turns, all of which can be complex and difficult to describe. The wood of the inlet, sometimes quite thin, is the only resistance to all these movements. If the particular part of the inlet receives a breaking force, then it means that the other, adjacent parts did not provide sufficient support for the moving action.

Sometimes we say that the breaking part has a "high point". There are three major conclusions to make at this point about the breaks of inlet. First, the receiver does not have equal support of the stock inlet at all points around the metal. In other words, there are high and low points, where the high points are taking the beating and the low points are excluded from supporting the receiver.

The arrow points to the breakage with deep wood removal. Filling this recess with epoxy will make this part of inlet stronger. Second, there is a movement of the receiver in the inlet during the shot, even if it is not detected otherwise. Without this movement no part of the inlet can be moved and broken off. Third, the strength of the wood is not sufficient for taking the hit.

For preventing damage and breaks of the inlet we need to exclude movements of the receiver, provide equal support of the metal all around the inlet, and increase the wood strength. A good way of doing that is by glass bedding. Since the 1960s when epoxies came to wide use, glass bedding This gel allows 30 minutes for distributing around the inlet and removal of the external runs. was finding more applications in gunsmithing, mostly in rifle accurizing.

In essence, the hard epoxy is used to build a bed for the receiver eliminates empty spaces under the metal, prevents movement there, and provides a strong base indifferent to moisture and temperature while excluding wood squeeze. This is exactly what we need for saving a shotgun inlet. I’ll use an example of how I’ve made this repair. First, the area with the breakage has to be degreased. This is especially important for the inlet as this part of the stock is often saturated with oil from the mechanism.

I use laundry detergent with hot water in mild cases and an industrial strength detergent for really heavy grease. Easy-Off Heavy Duty Oven Cleaner is one of the best. Drying the stock after washing should be gradual to avoid warping. After drying the broken piece, glue it in place. If the broken piece is lost, make a replacement matching the grain and type of wood to the original stock. At this point we have an option to shape the piece for better resistance to the shock.

For gluing I normally use the heavy viscosity superglue with a 20 minute setting time. It is important to have excess glue coming out of the break to make sure that all the empty spaces are filled up. After applying pressure, by whatever means, the excess glue should be quickly removed from outside. After glue has dried, shape the wood outside and inside for inserting the

Some internal cleaning is still in order. receiver into the inlet. The shaping outside is quite rough at this point; we will return to it later. Now we’re ready to start the glass bedding by removing the wood inside the inlet where metal is touching it. I perform this wood removal with Dremel tools. The cuts go all around the inlet but not touching external surface of the stock. Doing this ensures that the glass bedding will be invisible outside.

The amount of wood removed inside is your choice, however, since all of the removed wood will be replaced with a high-strength epoxy, the more wood removed yields a stronger final result. This is especially important when removing wood at the place of the breakage as that point is a known weakness. Prior to putting epoxy into the prepared space, take care that all parts of the receiver touching epoxy has a thorough application of release agent all around it to prevent gluing to the stock.

This release agent is a spray which makes application very easy. All screws for attaching receiver to the stock have to be covered as well. Missing any spot of receiver-to-epoxy contact with will glue the receiver "dead" to the stock and lead to disaster. My preferred release agent, Brownells Acra-Release Aerosol, does not require a drying time and the receiver can be immediately put in and touch the epoxy.

There are a number of useful epoxy options provided it has two qualities—it is a gel and it becomes really strong after hardening. I prefer Lam Lock Rocket Gel as it gives about 30 minutes before hardening and then quickly becomes very hard. This makes it easy to work with for about a half hour and then hardening continuing for several hours. Packing the prepared spaces with gel should be excessive to achieve complete filling of all empty spaces.

Gently squeeze excess epoxy all around the contact, quickly removing the external excess that oozes out. The 30 minute setting time helps with easy removal. When that is done, secure the parts together to allow sufficient time for curing—and hope enough release agent was used so that permanent gluing is only between the wood and epoxy, not the metal.

After hardening and allowing the set gel to take a perfect and strong mirror image, the receiver can be carefully installed into the inlet with all attaching screws tightened. Extracting the receiver from the stock after the epoxy is hardened should be done carefully. Excessive force may damage the stock. Epoxy excess inside inlet needs to be removed, making sure that springs and other parts are not glued anywhere.

Sometimes, after removing the action from the stock there may still be empty spots where the epoxy created an air bubble. These spots have to be filled with epoxy again, the action again thoroughly coated with release agent, and the process repeated. Remember that we are trying to reach the full support of the action all around the inlet with no empty gaps. When the epoxy-bed of the receiver is built to our satisfaction, we can take care of the external surface of the break.

If done properly, nothing should be visible outside. Conclusion Cracks and breakages of the shotgun inlet happen often and sometimes make the stock unusable. This problem can be explained by the complex movements of the receiver during the recoil and counter-recoil. Insufficient contact between action and inlet exacerbate the situation. These damages can be fixed (or even prevented) by glass bedding.

Building a layer of epoxy all around the receiver strengthens the wood, eliminates movements of the receiver, and provides a solid base. This epoxy base, unlike the wood, is indifferent to moisture, temperature, and oil. AG