Some boxes of 60gr vmax say 3030fps some boxes say 3173fps - Ammo, Inc. Signature .223 Remington 60 grain V-Max Brass Cased Centerfire Rifle Ammunition

Some boxes of 60gr vmax say 3030fps some boxes say 3173fps. The stuff seems to shoot ok, but individual boxes on some orders say 3030fps then a case will say 3173 fps??? I tried contacting the manufacturer a month ago and zero response. I wouldnt pay much for these or depend on them for consistent accuracy.