TTNs often develop a little slop. It's also not all that unusual to have them come out of the box with "a little slop." What to do depends on the cause of the slop. If it's vertical looseness after lockup, the locking lugs can be peened where they mate the locking bar. Depending on the circumstances (I can't see the gun nor fondle it), the answer is to do nothing. A TTN is prone to sloppy. So long as the guns isn't hoping open when fired, nor miss-firing, I'd normally suggest you ignore it.
Coffinmaker