While not the typical job that comes through the shop, it was quite an enjoyable diversion from the usual doublegun work. This started as a plain barrel Model 12 in 20 gauge and like seemingly every Model 12 on Earth, it's been reblued at least once. The owner (who is a good friend and colleague) is going to restock it and refinish the entire gun for his daughter and he wanted a solid rib installed. Not really for any reason other than a Model 12 always looks better with a rib. It enhances the "lines" of the gun and makes it look finished, while the bit of extra weight forward certainly doesn't hurt the gun's handling. NOS Model 12 ribs are pretty hard to come by and I didn't have a solid rib donor barrel to take it from, so it was made from scratch. The material for this project is 12L15, which is a resulphurized and rephosphorized steel with lead (hence the L in the designation) added to further enhance its already exemplary machining characteristics. With a yield strength of around 35KPSI, it's a perfectly suitable choice for a non-structural part such as a rib. Making it from scratch also allowed me to make it of a width that looked good when mounted on that small-diameter barrel.
Unlike the factory rib, I hollowed the inside of this one to within a half-inch of the muzzle. This saves a bit of weight but more importantly, it makes it a bit easier to get a skin-tight fit to the barrel when blacking it down (fitting to the barrel contour).
In this photo, the barrel appears to actually be "swamped". It's really a bit of an illusion caused by a combination of the barrel taper, and the vertically tapered rib.
The rib was serrated by hand. The guide lines were scribed .025" apart, using a height gauge and surface plate and then deepened using a carbide single-line checkering tool. The two outermost serrations were cut twice as deep, using a purpose-made cutter, in order to "frame" the serrations.
The next step was to tin the barrel and underside of the rib. After cleaning all traces of corrosive flux, the rib was clamped in place and soldered down permanently. Once all of the rosin residue was cleaned, the excess solder was cleaned up, the hole for the sight bead drilled and tapped and then all was reassembled for return shipping
Nice work and certainly a bit unusual.
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