My current favorite priming horn is a little Colt Baby Flask. If carries well in the pocket and gives good flow control. It will handle any grade powder. Since I load once from a pre-measured container but prime a few times while hunting, it is easy to use without opening another vial. When I have primed with 3F I have had no issues, although I prefer 4F or Null B when shooting in a match.
ADK Bigfoot
ADK Bigfoot