A couple years ago I related that a friend in Seattle SEATAC had to remove his guns from one of the big plastic black golf club shipping containers (Pelican ?) and have his wife bring a "regular" hard sided gun case to the airport for him to use. The gate agent refused to check his gun in what she said was a "golf" case as it was not a "gun" case. Then, the locking issue wasn't as important as the fact that it wasn't a "gun" case. He even met with the supervisor and the super would not overrule the agent even though he agreed with the gun owner that the "golf" case was in fact a "gun" case.
No problem, I often have additional "hardware" inside. You need to confirm with your carrier, though - they may have restrictions of their own.
