243 Winchester
Introduced by Winchester in 1955, the .243 is a necked down .308 case. Accuracy is inherent in this 6mm round and the various bullets available make it extremely versatile and popular.
A 20 degree shoulder and a case length of 2.045, allows plenty of room for the powder to generate in excess of 3000 fps with ease. The recoil is very tolerable combined with a muzzle blast that won't break glass making it a pleasure to shoot.
Spitting 60 grain bullets over 3700 fps, the .243 can ruin a varmints day in less than a heart beat. The .243 also has the ability to move a 100 grain bullet over 3000 fps having the same affect on white tail size game.