Its not advisable to change springs on the MP. I am not familiar with the Mass. guns, however stoning the sear block is the way Burwell does the MP as far as lightning the trigger pull, polishing a few other spots smooths it out. I used his well done directions and pictures. Its not difficult at all. I had an MP that started out five pounds eleven oz., it is now four pounds eight oz. and very smooth. You start changing springs you will risk light primer strikes, why go there if not necessary.