Henry Big Boy Cantilever Scope Mount Model BB-CSM To optimize accuracy, Henry Scope Mounts are available for all Henry H004 series Golden Boy, H006 series Big Boy and H005 Mini Bolt models. Each of these rifles now come drilled and tapped for easy scope mount installation. Our H001 series lever action rifles do not require use of these mounts as the receivers are 3/8ths groove. The Golden Boy Scope and 1st generation Big Boy rifles are drilled and tapped under the rear sight. Current production (2nd generation) Big Boys are drilled and tapped on the top of the receiver. To determine which generation of Big Boy you have refer to the serial number table provided so you select the correct mount. Instructions on installation of the scope mounts is provided in the packaging. All Henry Scope Mounts accept Weaver style detachable 1 top mount rings (rings not included). Note to Big Boy owners In September 2011 we began shipping the 2nd generation Big Boy rifles which feature receivers that are drilled and tapped for the scope mount. In previous production 1st generation the barrels were drilled and tapped if rollmarked Bayonne NJ. First generation Big Boys use the BB-CSM Cantilever Scope Mount. 2nd generation current production use the new style BB-RSM Receiver Scope Mount. 2nd generation Big Boys start with the following serial numbers: H006 = BB0047222 H006M = BB0015530M H006C = BB0021188C