Originally Posted by ModGlock17
Then it is far less than 17lbs or 23lbs at full battery. And it would be a bit more involved to understand the actual force at full battery on a stock spring vs. a replacement spring (perhaps even a variable or torsional spring). Such data never got quoted to compare and we replace them at will.
In doing my spring measurements, I found that in the G20/21 pistols, when the slide is all the way to the rear, the recoil spring is very close to full compression. Not all the way, but enough to make the approximation that full compression force is pretty much equal to the force when the slide contacts the spring.
Here's an image of my spring testing. Hopefully some of you will be as disturbed about this as I was. Note the chart of the ISMI 17# spring (slightly heavier than a new Glock stock spring), and then notice how the 20# and 24# springs are only marginally heavier than the 17#? (Again, the high load numbers are at almost full compression; the only way those 24# springs would yield 24# is if they were compressed all the way, and pushed some more.)
I have not tested any Wolff springs; I've heard they are closer to the rated weight but they don't work in a long slide.
Edit: the "dual spring" that gave the 28.5# result is one of those Sprinco-type "recoil reducing" guide rods, with a small inner spring supplementing the main recoil spring.