A method of assembling a surgical instrument includes inserting a knife into a knife guide and positioning the knife and the knife guide within an inner shaft. The method also includes moving a drive collar stop along a longitudinal axis defined through the inner shaft, engaging a pair of opposing projections of the drive collar stop within a corresponding first pair of opposing apertures defined in the inner shaft, and moving a drive collar along the inner shaft. The method also includes moving a spring along the inner shaft, compressing the spring, moving an inner shaft stop transverse to the longitudinal axis defined through the inner shaft, and engaging a pair of opposing projections of the inner shaft stop within a corresponding second pair of opposing apertures defined in the inner shaft proximal to the first pair of opposing apertures.
