A multi-caliber firearm has a breech sleeve connecting a barrel to a receiver and a stock. The stock includes a forward V-block and a rearward V-block. Each of the V-blocks defines a V-cut along a top portion and a through hole substantially aligned with the cross-sectional center of the V-block. The forward V-block extends through a cutout portion of the receiver and into the breech sleeve. The breech sleeve is fastened to the stock through the through hole in the forward V-block to provide a rigid connection between the stock and the breech sleeve. The receiver is fastened to the stock through the through hole in the rearward V-block to provide a rigid connection between the receiver and the stock.