SAWs and spring degradation - now with DATA!

[Hillslam]

Guys,

After our discussions on spring wear, and lubrication and cleaning and whatnot, wanted to post what I've found tonight.

I do alot of cleaning and lubrication to keep the gun firing as best it will, but I've become convinced the spring is losing power, and my chrono is agreeing with me. Try as I might I couldn't get the fps up to where the the gun fired when I first put the new spring in (M120). So tonight, after having the current M120 out of the gun for about a week, I fired it again to get some numbers. First shot: 370fps on .25g bbs. After a couple shots, back down to 320fps or so on the same .25s. This spring has about 20,000 rounds on it.

Next I put in a new M120 that had not been used. 370-380fps consistent. Still with .25g bbs.

Next I put in a Prometheus 135 spring (also new). 385-390fps consistent on the .25g bbs.

Since I removed all the other variables (the gun has been meticulously cleaned. The mechbox, gears, piston, cylinder, hopup chamber, and inner barrel all inspected for looseness and operation, cleaned and lubricated. The spring was not left compressed before the firing session. And I've been tracking my fps over the life of the first M120 spring) - I conclude that the fps loss is due to spring cycling.

Or - as a rule of thumb: 50fps per 10,000 rounds on the high side. Give or take.

Those are my numbers, thought I'd share the data. I'm going to go forward with the prometheus spring and measure its degradation. (I'll report back on it after about 10,000 rounds.)

Whoever said "springs are cheap, I just put in a new one in" seems to have the right idea, and my conclusion; If your numbers aren't up where they should be, and you're sure you're clean and lubricated correctly, and some mechbox part isnt tits up - replace that tired spring.