Abstract: We disclose a new switch-barrel system for firearms, particularly centerfire rifles, which permits the ready exchangeability of barrels upon a single action/stock assembly. Barrels may be quickly and easily exchanged under field conditions using a minimum of simple, lightweight equipment, without removing the action from the stock. Barrels of many different weights and calibers may be used on a single firearm, leading to great versatility. Barrels are free-floating in a manner similar to most benchrest rifles, ensuring uniform barrel harmonics upon firing. The system relies on a secondary set of fine-pitched threads and a locking ring to effect the securing of the barrel to the action, which acts to repeatably draw all barrels into invariable coaxial alignment with the action, thus insuring a return to essentially the same point of impact. The system is adaptable to a broad range of existing firearms, and does not require a proprietary action.