Axe Mastery 3 and Archers

Axe Mastery 3 allows a character to treat any axe or pick as possessing the thrown descriptor. As archers have proficiency with all martial weapons that possess the thrown or projectile descriptor, this feat allows them to use battleaxes, greataxes, heavy picks and the like as if they were proficient with them, even when using them to make melee attacks. They would still use their reduced melee Base Attack Bonus when doing so, however.

Axe Mastery and Berserkers

Berserker DR works just like armor DR in IH. Axe Mastery applies penalties to a berserker's DR rolls exactly as it would a character in armor. This includes the penalties from Axe Mastery 7, as the character's heavy blows overcome the berserker's resistance to pain. However, because the berserker has no actual armor to repair, he automatically recovers from Axe Mastery 7 penalties at the end of the encounter, with no Craft check required.