i had a 24-70 on both my A350 and A700 with no problems,but the gears on my sigma 105 macro were stripped by my A350,but repaired under warranty,and has been fine since.if my memory serves me right,marc[fabs]had the gears stripped on his sigma 24-70 a few years back.i'm not completely sure,but i think sigma have "beefed" up the gears on recent lens that are sony fit,although the problem seemed to be with how powerfull the sony motor is.