SxS Locking Mechanisms

A "bite" is a place where the barrels lock onto the action. The most common in side-by-sides are the "double underbites", sometimes called Purdey underbites. These are 2 notches on the bottom of the barrel that receive 2 sliding locks and are operated by the gun's opening lever. Some over-unders have underbites but they're mainly found on all side-by-sides. When gun makers get elaborate, like the German ones do, they include a "third bite" which makes for an even stronger lock-up. This is usually an extension from between the barrels that fit into a slot on the top of the receiver. The extension fits into a recess either between the firing pins or into a slot on top of the frame. Sometimes the extension has a hole in it through which a crossbolt slides through. The crossbolt version is called the "Greener Crossbolt" and is most common on German guns like Merkel. Side clips are even more elaborate and add even more strength to a side-by-side. The purpose of the side clip is to prevent any lateral movement of the barrels when fired. The place where the firing pins extend from is called the "face". The rounded area surrounding the firing pins is called the fence. There are two fences on a side by side, one for each barrel. Sometimes the fences have semi-circle "ears" coming off the side of each fence that fit perfectly around each side of the barrel where it's been filed to accept the "clip". Look at the AYA from the side......see the semi-circle "clips" that extend a little over each side of the barrel? When the double underbites are combined with a Greener Crossbolt and side clips, you end up with the strongest and most desirable of all locking systems. You may not need all of those with modern metals, but it sure is nice to know that they are all there. They are very expensive to add which is why most makers don't employ them.