Your RAM isn't 1600 MHz, it's 1600 MT/s. Since we're talking Double Data Rate, that's equivalent to an 800 MHz clock.
It's very common for the BIOS/UEFI to default 1600 MT/s RAM to 1333 MT/s. Simply go in there and select the XMP profile for 1600 MT/s.
okey dokey, I'll try that! Thanks