Tcall builder, To silver solder a base onto the barrel the base must be steel, the H&R bases are alloy, can't solder them on. Try a base by TC for the Encore, I have heard the contour matches the 12 gauge H&R pretty well and there are 4 mounting screws on the base, or contact Brownells, they may have a steel base that might match. To silver solder you have to get the barrel VERY hot, possibly to hot in the chamber area, check with a GOOD gunsmith. Of course a GOOD gunsmith would probably drill and tap the barrel, many have been done that way with no disasters that I have heard of yet. It seems to work even though H&R says not to do it. Make sure your gunsmith does not drill through the chamber wall and possibly attach the mount with a total of 3 or 4 screws if you could instead of 2. You could even have the gunsmith adill 2 more mounting holes in the alloy H&R mount. Remember they are only in a short/shallow way. That is why the TC Encore (fits the 12 gauge barrel contour closely) mount is so good, 4 screws....<><.... :grin: