Factory Savage Arms bolt assemblies are great for building switch barrel rifles. If changing calibers that use different size bolt faces, complete assemblies are more convenient than changing the bolt face in the existing bolt. These bolts do not work on the pre-110 series rifles such as the model 340. Fits 10 thru 16 series and older 110 thru 116 series. Notes: Early Savage centerfire rifles 10-16 and 110-116 have a flat rear receiver, later and current models have a round rear receiver. Current bolt assemblies have a round collar to match the round receiver. Bolts operate in exactly the same manner as the flat collar bolts