Abstract: The present disclosure provides an adjustable attachment system and method that can adjust for a variety of gaps between an accessory mounting system and a weapon mounting system, caused by tolerances in manufacturing. In at least one embodiment, a combination of keys can be provided with a first key having a thickness that is in a middle range of a predetermined tolerance, a second key having a greater thickness by a given percentage, and a third key having a lesser thickness by a given percentage. One or more of the keys can be coupled between surfaces of the accessory mounting system and the weapon mounting system, depending on the gap size. In another embodiment, at least one key can have a tapered lateral surface. The variable sized key can compensate for the variety of gaps by the lateral position of the key in the gap.