for the inclined surface 25 of the cover 24 which in assembled position overlies this portion of the stabilizer to summarize the operation end 28 of the stabilizer is clampingly held by the opposed surfaces of the u shaped shank 11 of the shuttle spring in addition to serving as a means of support for the stabilizer its end 28 serves to replace the conventional filler block normally carried within the u shaped shank to resist the clamping forces of the cap screw 21 for fixing the shuttle spring in the shuttle the surfaces 33 and 34 which form the sides of end 29 of the stabilizer are disposed so as to engage opposed surfaces of the gripping jaws 13 and 14 and serve to maintain the latter in an outwardly flexed predetermined position during the absence of a weft bobbin therebetween by holding the gripping jaws outwardly from their relaxed or unflexed position less camming force is required to spread said jaws a sufficient distance during transfer to receive a fresh bobbin during the interim period which is that period during the driving out of the spent bobbin and before a fresh bobbin is in clamping position between the jaws the stabilizer is effective in preventing the jaws from flexing inwardly beyond the sides of end 29 of the stabilizer by preventing such flexing of the gripping jaws the high frequency vibrations set up during transfer.