Stripping and Relaying Ribs

Stripping and Relaying Ribs | Shooting Sportsman Magazine

"Buy the barrels” is a colloquialism I have often heard. While I think there are many aspects involved in assessing the overall condition of a gun, the integrity of the barrels is the one most commonly overlooked. Unfortunately, if it is necessary, barrel work is by far one of the costliest gun repairs.

Double-gun barrels consist of several components that make up the “barrel set.” The barrel set typically includes two barrel tubes, two long ribs, a forend loop, a little rib, barrel lumps, and/or a monoblock. In some cases the forend loop and little rib are an integral piece. In the case of “chopper-lump barrels,” the barrel tubes and one or both of the lumps are integral. These components are all held together with braze or solder. Braze and solder are non-ferric metal compounds that form chemical bonds with the ferric metal of the barrels. They are the metallic “adhesive” that holds everything together.

In the case of “brazed” barrels, the brazing material can be made of copper, zinc, silver or tin. Brazing takes place at relatively high temperatures, typically above 900°F. Brazing barrels together is typically done on lesser-quality guns, although I have seen a few high-grade guns with brazed barrels. Compared to soldering, brazing is a relatively fast process, and the braze joints are incredibly strong. The most significant problem with brazing is that it occurs at such high temperatures that once the process is completed the barrels cannot be altered. This can be an issue with adjusting barrel regulation or if one of the barrel-set components needs to be replaced.

In the case of “soldered” barrels, the tubes and barrel-lump assemblies are brazed near the breech, and then the rest of the barrel components are soldered together. The solder used in barrelmaking is usually 60% tin and 40% lead, although some makers use pure tin. Soldering temperatures are typically around 450°F. The benefit of soldering is the relatively low working temperature of solder. The barrel set can be sub-assembled and altered during and/or after the initial assembly process. Barrel regulation can be checked and fine-tuned, if necessary, and if one of the barrel components is damaged, it can be removed and replaced. The downside of soldering is that it’s a hot, messy and arduous process.

Due to unfortunate circumstances, one of the solder joints may fail and one of the barrel-set components may become loose. This is referred to as having a “loose rib.” Once a loose rib occurs, the entire barrel set may need to be disassembled, cleaned, repaired or replaced, and soldered back together. This process is referred to as “stripping and relaying the ribs.”

The need for stripping and relaying ribs can arise from several different circumstances. One is some type of physical trauma that knocks one of the barrel components loose. In these cases the tubes must be thoroughly checked to make sure they are not damaged.

Another common cause of loose ribs is that the barrels were repaired with or initially soldered together using an acid- or mineral-based flux. Flux is the cleaning agent used in the soldering process to deoxidize the surface of the barrel material and allow the solder to bond to it. The problem is that there is always a small amount of it left behind. Flux residue left in the joint is the biggest problem. Acid or mineral flux is hugely hydroscopic, meaning it attracts water molecules and causes compounding oxidation (rust), and in most cases this happens between the ribs and barrels where it cannot be cleaned or arrested.

The flux that is traditionally and appropriately used for barrelmaking is rosin flux. This flux is nothing more than highly refined and concentrated pine sap dissolved in pure alcohol. Using this type of flux can be a bit harrowing if not done with great care. Aside from being burning hot, terribly sticky and ridiculously flammable, it does have one very desirable characteristic. Once heated, it becomes completely inert and will cause absolutely no oxidation or corrosion. Many gunsmiths detest using rosin flux, and I will admit that it’s not pleasant to work with; but I feel that it’s worth the trouble in the long run. A joint that is properly fit and soldered with rosin flux will virtually last forever.

Another cause of loose ribs is when soldered barrels are “hot caustic blued.” The hot-bluing process is used on modern guns that don’t have parts that are soldered together. This process uses a hot caustic bath to turn the metal black. The salt bath aggressively dissolves the solder joints. I have seen barrel sets literally fall apart after being subjected to this process. Soldered barrels should be “rust blued,” or “blacked”—a process in which successive layers of black oxide are built up on the barrels in a fashion that does not harm the solder joints.

When a set of barrels needs to have its ribs stripped and relayed, the first thing I do is take a detailed set of measurements of the barrels. I measure the center-to-center dimension of the bores in two-inch increments from the muzzles to the breeches. Double-gun bores are not linear or parallel to each other. To facilitate proper point-of-aim regulation, they actually suck in toward the middle of the barrel set and flare out slightly near the muzzle. If these dimensions are not meticulously maintained, the barrels will not stay regulated after the ribs are stripped and relayed. An accurate measurement from the rear of the forend loop to the front of the forward barrel lump is taken, because if this distance is not maintained, the forend will not fit back on properly.

Once all the measurements are taken, the barrels are held in a vise by the lumps, a large propane torch is used to heat and melt all the solder joints, and the barrel set is completely disassembled. Most fine guns will have a series of “packing blocks” wedged between the barrels. These typically are thin copper or brass sheets rolled up to get the desired thickness. The “packing blocks” set the spacing between the barrels and help facilitate proper regulation. Their positions must be measured and recorded before they are removed.

All the component parts are then thoroughly cleaned. This is done by heating them with a torch and scrubbing off the rust and old solder with a fine-bristle wire brush. This is a time-consuming, hot and dirty process, but if the parts are not cleaned to the bare metal, the solder will not bond well.

Once all the parts are cleaned, they are inspected for proper fit and condition. At times new ribs or a new forend loop might need to be made. Some refitting is almost always necessary, and if the fit between the pieces is not precise, the joints will not hold well.

Then the surfaces of all the joints have a thin layer of solder and flux applied to them. The parts are heated with a torch, the flux and solder are applied, and when the solder liquifies, it is scrubbed onto the metal with a fine-wire brush. This is referred to as “tinning,” and it creates a very strong bond between the solder and the metal parts.

At this point all the component parts are reassembled and held together with iron binding wire and clamping fixtures. The clamps and wire are adjusted so that the previously recorded barrel dimensions are exactly the same. Rosin flux is liberally applied to the joints, and the entire barrel set is heated to the point that the solder is liquified and flows together. The joints will settle a bit as they are melted together, so all the measurements must be checked again and the wire and clamps adjusted accordingly. Any of the joints that look “thirsty” have additional flux applied and solder melted into them. The barrel set is then left to cool. I will say that if you have never witnessed this part of the process, it is quite a spectacle. Ladling pine sap suspended in pure alcohol onto a 450° barrel set with one hand while holding a large torch in the other can get rather . . . exciting, and flame-retardant clothing is recommended.

When the barrel set has cooled, the flux will have hardened into a thin layer of brittle toffee-like material coating nearly everything. The clamps and wires are removed, and the hardened flux is cleaned off with a large fine-wire brush. All the joints are then checked, to make sure they are properly sealed with solder. Any excess solder is painstakingly removed with brass scrapers and chisels, and care must be taken not to dent or damage the barrels. This is another dirty and arduous task. When properly done, an almost invisible line of solder should be seen along all the joints.

The barrels are then sanded and polished to be made ready for rust blacking. During the sanding process, wood and cork forms are used to hold the sandpaper to make sure the corners and edges are kept fine and crisp. If it was necessary to polish over any lettering or engraving, that is now recut. There are few things as awful as seeing a freshly blacked set of barrels with washed-out lettering or engraving.

The barrels are now checked for proper fit back onto the action and forend. The gun is test-fired to check for proper barrel-to-barrel regulation. If the regulation is off, the barrel dimensions will have to be readjusted and much of the process repeated. Hence why so much attention is paid to the barrel dimensions during the initial soldering process.

I hope this description of stripping and relaying ribs in the traditional manner makes evident how labor-intensive, meticulous and hazardous it can be. I also hope it demonstrates why when purchasing a gun, a thorough inspection of the barrels is of extreme importance.

Delbert Whitman Jr. lives near Traverse City, Michigan, with his wife and daughter. He is a professional gunsmith specializing in repair, restoration, stockmaking and engraving. He also is a passionate upland-bird hunter and an English cocker spaniel and French Brittany owner.

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