Be sure to pull over after the first five to ten miles of towing for the first time then put your hand on the trailer wheel hubs, if it stays cool; it is packed with some good amount of ball bearing lube.
My M416 isn't ready after I picked it from the Marine Base. My in-depth inspection is not allowed on their military base after purchasing the trailer thru internet.
The trailer wheel hub was really HOT after five miles so I went to a nearest auto store and grab some rubber gloves and two cans of lube. After removing the wheel hub caps with large flat screw, there is no remaining of lube left. I removed the ball bearings for a sign of warp or deformed but only mild purplish.
I just stuffed new lube as much as possible with my hand (w/ rubber gloves) then after two more pull over on the highway to check the temp of wheel hubs. It remained cool for another 400 miles.