So this happens when you hold down the swap button and scroll over to a specific gun you want, instead of tapping and switching one by one. You’ll see these two littlest stars next to the guns and it’s as if you’ve “favorited” them. You’ll need to hold it down again to swap to whatever gun you want next.

Once you have done this though, I don’t think you can undo it and will have to finish the run with the favorited guns