A rifle includes an upper receiver body, a lower receiver body detachably attached to the upper receiver body, a stock and a bolt carrier group. The upper receiver body has a bolt carrier receiving bore exposed at a stock engaging portion thereof. The stock includes a recoil spring receiving bore therein exposed at a mounting portion thereof. The mounting portion of the stock is engaged with the stock engaging portion of the lower receiver body in a manner whereby the recoil spring receiving bore is accessible from the bolt carrier receiving bore. A centerline axis of the recoil spring receiving bore is skewed with respect to a centerline axis of the bolt carrier receiving bore. The bolt carrier group has a bolt carrying structure slideably disposed within the bolt carrier receiving bore, a recoil spring engaging structure slideably disposed within the recoil spring receiving bore and a linkage member structure pivotably engaged between the bolt carrying structure and the recoil spring engaging structure.