After publicising the route, they wouldn't have changed it at the last minute because there were thousands of people all lined up to watch the motorcade.

As Oswald worked at the book depository, he could have take the gun there before the day but a witness said LHO carried a brown paper package in on the morning of the shooting but LHO said he only took his lunch box in that day. The gun came apart so it was easier to wrap/disguise, then it would be less than 3 feet long.