I don't know if this is a side effect of the algorithm that calculate when a weapon is degraded or whatever but I have an smg with 1900 durability and it get degraded around 500, It seems a little high to me
I have a pistol with 1400 durability and now it's at 467 and it still hasn't degraded. (i often use burst and it damage my SMGs a lot, sometimes I have to take a weapon from the inventory during combat, lol)