My Victory is about 400 rounds old and I have the same problem.
After about 50-75 rounds I have to retighten. Contacted S&W and here is their reply:
"Dear Customer,

We apologize for this inconvenience. We will send you a new takedown screw. Your order number is xxx.

If you are still experiencing this issue with the new screw, we would recommend sending the pistol in for evaluation.

Smith&Wesson values its customers and we are happy to have served you today. Please do not hesitate to contact us should you require further assistance.

Maybe if all of us who have the problem email them they might get the message that there is a problem.

I also bought a "T" handle wrench (Model # JTH6E13) $4.99 from Home Depot - that works well.
)