220 Swift was my caliber for varmint hunting and very fun caliber to reload for. 4000+ fps for factory 40gr loads are available and folks that have hit over 4700 fps with their custom reloads. High quality barrel, slow rate of fire and good maintenance are key to long barrel life. Even with these factors, typical barrel life is inside of 2000 rounds. Impressive results shooting Barnes 36 gr varmint grenades at 4200 fps.