Hi, Since kernel 4.9, despite setting CONFIG_EXTRA_FIRMWARE="iwlwifi-7260-16.ucode" the kernel looks for iwlwifi-7260-17.ucode This ucode while available in the kernel tree is not part of sys-firmware/iwl7260-ucode.
The site offering the packageable downloads does not offer the iwlwifi-7260-17.ucode : https://wireless.wiki.kernel.org/en/users/Drivers/iwlwifi If it helps, the following command does provide it in /lib/firmware/iwlwifi-7260-17.ucode : emerge -av =linux-firmware-20161005
*** This bug has been marked as a duplicate of bug 602470 ***