A fixing mechanism includes a mounting plate of a small arm accessory, a fixing member and an adjusting member. The mounting plate has a surface that faces the small arm when the mounting plate is fixed to the small arm. A first direction is defined as normal to the surface. The fixing member extends from the surface of the mounting plate in the first direction. The fixing member includes an aperture defined therein having an axis that defines a second direction different from the first direction. The adjusting member provides a fixing force to fix the small arm accessory to the small arm when inserted into the aperture of the fixing member.