Also, firing pins on Smith guns are not spring loaded so the extractor face moves those pins rearwards on opening. Thus the protruding ends of firing pins will cause some resistance on opening; and at this point you aren't sure those pins are the correct length, they could be too long? Remove firing pins and try opening the gun, if there's no resistance else where then the problem is with those pins. If there's still an issue then you'll at least know what it isn't.