Ive ordered an S.G.C Speedmaster, which I should hopefully get within the next two weeks. Will be used for foxing. My neighbour has one and Ive been out with him quite a few times and have never found it any bother. I think what you have to consider is whether you are going to be shooting from vehicle, when prone and general "stalking".
When Ive been out with him, we have clean kills out to 450yds and that is from a vantage point where known paths are for the foxes.
I cant say Id use it to walk 100 acres though!
If you do look at some AR's, forget the rear charging handle ones!
Its really YOUR choice! The advice is not bad advice though.
Wil