Originally Posted by Donald
I just received and installed my Kimber revised flat wound spring and new guide rod.
Wow! That's a colossal difference. Springs are fascinating devices, so your picture caught my attention.
I don't have the gun or springs in front of me. I don't have measurements or specs. The following are just some thoughts as they flow from brain to fingers, so feel free to correct my thoughts where I go astray.
These are linear rate springs. They'd be measured in (x pounds/inch) of compression. Let's assume that the old spring is 3.5 pounds per inch. Slide movement compresses the spring 2 inches. When you install that short spring, you're compressing it .5 inch.
But the initial pressure holding the slide into battery is
That's less than two pounds pushing that round into the chamber and locking up the mechanism. If any of the conditions are less than optimum, then 1.75 pounds might not be enough to overcome the problem.
Now lets look at the new spring. Let's assume it's a 2 pound per inch spring. How much do we have to compress that spring when we initially install it? Maybe 3.5 inches? Let's do some math.
That's close to your guesstimate, Donald, and the same as the recoil spring in the Colt Mustang. But the big difference is the initial pressure holding the slide closed:
That's FOUR TIMES the force of the original spring, pushing that new round into battery.
Granted, the vast majority of the force stripping a new round from the magazine and chambering it, is the momentum of the slide. And that's affected by the friction of the rails, friction from excessive lubricant, excessively strong magazine springs, and a myriad of other variables.
These numbers are just made up, but you can see where I'm going with this, and probably why the boys and girls at Kimber decided to to make such drastic changes.