Foxes don’t like....

[Sausagedog 7,381]

And that is why I shoot them twice if I can. I mean I have seen many a fox go down and then get back up. They seem to have a short lived shock if not fatally wounded.

I often give them another for good luck.

[Alsone 789]

5 hours ago, Born Hunter said:

I've had foxes run on after being clipped by #4 at relatively close range, never had one run on when clipped by BB.

Owt will kill em when it all goes right. It's when it doesn't you want the right load and imo that is BB through a half choke. 

Anything from 3's to BB is a good choice. Personally I prefer 1's as more shot in the pattern but still a good size of shot, it's personal choice. That said I've never wounded a fox with 42 Gr No:1's. Instantly stone dead every one I've ever shot. Below 3's or above BB's and you increase the risk of wounding. There's a reason why tried and trusted cartridges are used for most species.  I'd also be very wary these days shooting fox with anything too small. If you wound and someone reports it, you're at risk of prosecution for causing unnecessary suffering. I can't imagine many experts willing to stand up in Court and justify using 6 or 7's against a fox sized target. Larger than BB's may be justifiable, but it's fool hardy given the lack of likely hits at range.