The 307 was introduced in the late 80's to give hunters 300 Savage performance from a carbine length lever action. As was stated the receiver walls were beefed up to handle the higher pressures associated with the cartridge and the case dimensions are that of a 308 with a rim. Winchester unfortunately introduced it about 30 years too late. Why have a 308 class cartridge with sub 308 performance and it never really took with hunters. Ballistally it is equal to the 300 Savage and slightly behind the 308 due to thicker case walls reducing internal capacity and the need to use 30-30 bullets. Factory ammo is not being produced but can still be found if you search long enough, brass is produced by Winchester on a seasonal basis. If you want something that may become collectable, buy it. Winchester 94 AE's are the only gun ever produced in 307, Savage did list it in the catalog but never went to production.