I assume that you mean that you have a mag with 25 rounds loaded & when you shoot, the first 5 rounds are a problem & the last 20 rounds feed okay.
If so, in my opinion, that sounds like an issue with the spring in the mag as it would change pressure as the number of rounds goes down.
Mine work fine . Can you try yours in another gun ? Can you try another mag in your gun ?
If your gun works fine with the factory mag then I would try & get the Butler Creek one replaced under warranty as it sounds to be defective.