Retaining Screw Blues

There are lots of Stevens Model 311, Fox Model B, and Springfield Model 511 double-barrel shotguns out there that have been passed down from father to son. Take, for example, the 16-gauge Stevens M311 shotgun brought into my shop recently. The owner spoke with a distressed pitch to his voice as he described the problems with the gun: "Sometimes it won’t open; the top lever is jammed. Sometimes it will open, but won’t shoot when I pull the triggers.

And sometimes it sounds like something is rattling around inside the action. Externally, the old gun showed that it had been well taken care of, but there were obviously some real issues going on internally. The rattling noise was the biggest concern to me. Without exception, every time I’ve worked on a Model 311-type shotgun with something loose inside it turned out to be a firing-pin retaining screw.

I won’t rehash the disassembly/ assembly procedures for the Model 311, as that was well covered in the July 1994 issue. But I will comment on my observations during disassembly, and provide you with a fix for the problems I found. Analysis of the Problem Making sure the gun was clear, I separated the forend and barrels from the action, and then the buttstock was removed. The buttstock had been removed before, as evidenced by the repaired wood on the stock adjacent to the head of the stock bolt.

This is a fairly common goof the inexperienced and careless make. It occurs when the screwdriver slips out of the head of the bolt and wedges between the bolt and the wood. Continuing to turn the screwdriver will break out or crack the thin wood of the stock. It’s relatively simple to repair, but often means there are other problems caused by heavy-handedness and inexperience. With the buttstock removed, pretty much everything you need to know about the Model 311 action is revealed.

The rattling problem was immediately obvious. The left firing-pin retaining screw was out of its hole and wedged between the left sear and the receiver. Both hammers were forward. The left firing pin and firing-pin spring were still in place in the receiver, as were all the parts for the right firing pin.

It appeared the left retaining screw had been rolling around inside the action for some time, and had jammed in several different places as evidenced by the number of burrs, nicks, gouges, and bends I could see on the internal parts. This would also explain the intermittent jamming of the top lever. I checked the hammers, sears, and sear spring for proper assembly and everything was correct.

I moved both hammers to the full-cock position by raising the front of the cocking lever with a stout screwdriver, using the hinge pin as the fulcrum for the screwdriver. Neither of the hammers engaged their respective sears. Visual inspection of the ends of the sear and hammer pins revealed signs of the heavy-handedness mentioned before. The hammer pin was actually installed backwards. The swaged splines on the end of both pins should be in the right side of the receiver, with the pins drifted out left to right.

From the amount of deformation on the ends of the pins, I suspected that no slave pin was used when they were previously installed. I removed the sear pin, both sears, and the sear spring. It was immediately apparent that the sear pin was severely bent. The long rear leg of the right sear was also bent slightly, though the left sear and sear spring were serviceable. Next the hammer pin, both hammers, and the cocking lever were removed.

The hammer pin was almost as badly bent as the sear pin, but both hammers and the cocking lever were serviceable. It was now apparent that the hammers and sears could not make

contact because of the bent pins. That would explain the failure to fire the customer described. The hammers could not stay cocked without sear engagement, and would ride forward when the action was closed. The left firing-pin spring and firing pin were removed. The right firing-pin retaining screw was loose. The right retaining screw, firing-pin spring, and firing pin were also removed at this point. The firing pins and springs were in good condition, while both retaining screws showed damage.

The retaining screws have oversize heads which not only retain the firing pins but also function as hammer stops. They take a beating every time the hammers fall, which is normal. Some of the screw threads, however, were damaged or missing, which is not normal. So far, it appeared as if all of the damage could be fixed with a few replacement parts. The last things I checked were the threaded holes in the receiver for the firing-pin retaining screws.

The left the receiver, deforming and then shearing off the threads in the receiver. It was obvious from the relatively good condition of the threads on the surviving retaining screws that the screws were much harder than the receiver material. The extra grip length of the new screws’along with thread-locking compound’ will keep them tight. could be repaired. There were two possible ways to repair the threaded holes.

One, install bushings in the damaged holes, then drill and tap the bushings for replacement firing-pin retaining screws. Or two, drill and tap the existing The Repair The return of this gun to a serviceable condition now hinged on whether the two threaded holes in the receiver The threads were stripped in both holes. hole had no visible threads, and the threads in the right hole were barely visible. The damage most likely started when the firing-pin retaining screws loosened and backed out of their holes.

Then every time the hammers fell they would drive the loose retaining screws into holes for new oversize retaining screws. I chose the latter approach since it was the logical one to try first. It would be much easier to just tap the existing holes for larger screws, and if that was not successful I would still have the option to install bushings. To measure the diameter of the stripped-out screw holes, I used the shanks of drill bits as plug gauges. I measured the left hole, which was the larger of the two holes.

A #30 drill was a snug fit, but a #29 (0.1360 inch) would not go. There is very little parent material between the firingpin holes and the retaining screw holes. Since a #29 drill is the tap-drill size for an 8-32 tap, this appeared to be the largest thread I could use without breaking completely into the firing-pin holes.

As you can see in the photo, the right retaining-screw hole had already partially broken into the firing-pinhole probably a result of the loose screw deforming the hole every time it was hit by the hammer. Fortunately, it broke into the firing-pin hole only at the top, and there was enough material in the rest of the hole to successfully tap it. I cleaned up the holes with the #29 drill, being careful to stay parallel to the old holes and to avoid making them deeper. The two retaining-screw holes are

Figure 1. Tap Extension Details 1. Make from 0.312" diameter rod approximately 5" long. 2. Drill hole in end approximately 0.750" deep to accept the shank of your tap. 3. Locate set-screw hole so it will engage flat driving surface of tap (approx. 0.50" from end). 4. Drill and tap set-screw hole for 4-40 set screw. 5. Cut some flats on end of extension to fit your tap handle. recessed into the backside of the breechface, and require extensions approximately 5 inches long.

I lengthened the drill by silver soldering an extension to the shank. I made the tap extension from apiece of 0.312-inchdiameter steel rod (see Figure 1). Now I was ready to tap. I gave careful attention to the angle of the tap to stay parallel to the old holes, and finished with a bottom tap to get as many threads in the hole as possible. Both holes tapped perfectly without any problem. The original firing-pin retaining screws had ahead diameter of 0.336 inch and thickness of 0.194.

The new screws would have the same head dimensions, and the threaded shank would be 8-32 by 0.337 inch long. Grip length was determined from the depth of the screw hole in the receiver (0.357 minus 0.020 inch for clearance. I wanted the longest grip length possible to help keep the screw tight and to better survive the pounding it would get as a hammer stop. Search as I might for an over-the-counter 8- 32 screw with the necessary head dimensions, I couldn’t find anything that was even close.

So, having no alternative, I made some new screws from 1/4-20 by 1/2inch-long socket-head cap screws. Even after turning the head to the final outside dimension there was plenty of material left around the socket to work effectively as a hammer stop. If you prefer to have a slottedhead retaining screw, you can use a solid hex-head screw instead, and cut in a screwdriver slot. I turned the shanks of the new screws to 0.164 inch and threaded them with an 8-32 die.

As for the other damaged parts, I replaced the sear and hammer pins, straightened the right sear, and dressed Figure 2. Slave Pin Details 1. Make from 0.156" diameter rod approximately 3" long. 2. On one end put a 0.250" long taper and bring it to a point. The other end must be flat with no chamfer. 3. A high polish on the pin and some lube will make it easier to use. the other internal parts to remove burrs, nicks, and gouges.

Assembly Notes When I installed the new firing-pin retaining screws in the receiver, I used "permanent strength" Loctite. This material provides a very strong bond and ensures the same failure will not be repeated. Use it sparingly and make sure you don’t get any Loctite on the firing pins or springs. If the retaining screws need to be removed in the future, the bond can be broken by applying heat to the head of the retaining screw using a torch with a small tip to localize the heat.

If you don’t already have one, make a slave pin like the one shown in Figure 2. You’ll need it to assemble the hammers, mainsprings, and mainspring plunger in the receiver. The slave pin is installed tapered-end first, right to left, and is drifted completely through and out the left side of the receiver when the hammer/cocking lever pin is installed.

Conclusions In the course of repairing this gun it became obvious that it had been disassembled by someone who was not a gunsmith; the damage to the buttstock and the incorrect assembly of parts were immediately apparent. Most likely, the firing pins had also been removed, and on reassembly the retaining screws were installed without thread-locking compound and were not tightened properly. Remember, the actions of all these guns are of the same basic design.

They all have a common firing-pin retention system, and share a common failure of that system. The stripped threads in the receiver could have meant the end for this old gun. Sometimes it takes making that special part to complete a repair. It may not seem worth the effort to salvage a relatively inexpensive gun like this, and sometimes the cost of the gunsmith’s labor is more than the owner is willing to spend unless the gun has a sentimental value. This one obviously did, and you can’t put a price tag on that. I