I have heard not to leave anything in the barrel as when the bullet goes down it, any "wet" residue is not displaced fast enough and it can warp/cause problems with the barrel staying true...Is this accurate, I don't know, but I am not willing to test on my barrels, so I just dry em out. If going in storage for long term, I put some lube down them, but dry em before shooting.
I am pretty fanatical about ensuring the bore is dry after each cleaning session.