I wrote on claymore's bat configuration -cclock 1400 the computer freeze and just with reset is rebooting. If i try to change this value with MSI AB is steel remain the default value 1340. With AMD drivers 23.20.782.0 ( 2.010.2017) is possible to change the gpu freq up to 1600 with MSI AB and the changes are semnificative ( 2-3 MH/s ).
Good luck killing your graphics cards!
Boy, how long ago have you heard first time about overclocking? Better sell away your rig and buy some Ether, you will earn more.