A LGS calls me whenever they get an Auto5 in, either for me to simply identify, usually clean, and sometimes repair. I get first crack at buying them often times. (It's a win-win! I went in yesterday to look at a 1951 Sweet 16 and a 1969 12 mag. Both were as dry as a popcorn fart. I lubed them up and bingo---smooth as a Belgian made Swiss watch. I did notice something I had never seen before....the recoil spring was darn near the correct length, telling me it had either been replaced or the gun hasn't seen a trillion rounds. However, the coils were noticeably closer together on each end, maybe the last three coils on each end. Every other recoil spring I have encountered-- new or well used-- had evenly spaced coils. Even well worn springs, some that were way too worn to be used, were simply shorter due to all the coils becoming closer together. This particular spring appeared to be progressively wound. I should had taken a picture! Anyone ever see something like that?
Not on Auto Five but definately on machinery. Closed loop progressive wound is for shock dampening cushion when a spring design is functioning high load repetitive use. It's probably been a hand wound one off by a clever individual or spring maker who really understands spring engineering principles and calculations. It will likely be something better steel wise and heat tempered than cold wound piano wire.
