There is a specification established for the op rod spring based on length of the spring and compression resistance. This is to ensure optimum functionality. A too short or weak spring will allow the bolt to batter and damage the rear of the receiver and will retard the forward action of the receiver after firing. A too strong or overly long spring will increase bolt velocity on closing and may cause the action to short cycle. There is a dimensional tolerance established for every part of this rifle to ensure correct functionality. If tolerances are below or above spec for any one part it can affect the correct interaction of the others. Extra strength or extra long op springs are a solution to a non-problem. If a spring is kinked, worn with flats or shorter than the specified length, replace it. If a spring is too long, as some commercially produced ones are, then cut it back to the max specified length.