Its worth mentioning that the 105 Amax run best with an eight twist barrel - Some rifles with a 9 twist will work , but stability is marginal and it usually has a detrimental affect on accuracy.
The standard 243 is fitted with a ten twist - therefore totally unsuitable for this bullet. So if the OP or any forum members are considering this bullet , they will need a tight twist custom barrel fitted to your rifle.
IME , For fox shooting, there are much better bullets than the 105 Amax . I think the vast majority of foxes are shot below 300 yrds ( in fact most below 200 yrds would be my guess) Therefore why use a bullet who's high BC benefits really only shine at ranges well beyond that ?
For foxing , I prefer a faster , flatter bullet, the offers better expansion, than the slower an more solidly build target bullet.
The lighter bullets also give more of a safety margin regarding pass through's or ricochet's and the felt recoil is noticeably less when shooting the lighter pills.
Just my 2 penny's worth
ATB
Alan