Most early low voltage Bi-Pin sockets used phosphor bronze leaf springs, which quickly lost temper, and gave a miserable performance as a long lasting socket. Here in Australia you see very few of the old spring types left. You do see a lot of the socket that has grub screws to tighten on to the lamp pins, and more grub screws to tighten on to the high temperature pig-tails. IMHO, no other method comes even close to giving you a reliable long term connection. Accept no substitutes!
Bill.