Lone Wolf Distributors is a good place to buy replacement Glock parts. Another place is Wolff Gunsprings; but, at Wolff you'll, also, need to pick up one of their non-captured steel guide rods.
http://www.lonewolfdist.com/products.asp?prod=61 http://www.gunsprings.com/SemiAuto/GlockNF.html Whenever you replace the recoil spring it is, also, a good idea to replace the firing pin spring as well.
A good INDICATOR of whether or not you need to replace the recoil spring on a Glock pistol is to perform this simple test:
First, remove the magazine and make sure the chamber is empty. After you've verified that the pistol is unloaded, elevate the muzzle at a 45 degree angle. Gently pull the slide back, and hold the trigger to the rear while you do this. Now, with your support hand placed firmly across the top rear of the slide slowly, 'ride' the slide forward. (Remember to hold the trigger back!) If the slide goes fully into battery, then, you've got a strong spring. If the slide stops just short of going into battery, but snaps shut at the slightest downward movement of the muzzle, it is still a fully functional spring - just, 'worn in'.
If the slide doesn't go into full battery at between 45-25 degrees, it is showing signs of weakness. Experience is your best guide. Depending on the degree of angle between 45 degrees of elevation and true horizontal, your Glock's recoil spring may need to be replaced. My recommendation would be to change any spring that doesn't snap into battery until after it's below 15 degrees or at true horizontal.
There is a caveat: Many brand new Glocks have failed this test; it used to be taught at the armorer's school and no longer is. You may take this opinion for what it's worth: High quality springs are NOT one of Glock's strong suites. The first thing I do with a new Glock pistol is call Wolff Gunsprings and replace every spring on board (except the depressor rod spring) with new high tensile strength Wolff springs.
A classic sign of a weak recoil spring is ejected brass that is thrown no more than a foot or two from the gun - Especially if the ejection line is, 'flat' with no arc to it. Another good indicator of a weak recoil spring is repeated FTF's with the last few rounds in the magazine failing to feed. I always make a mental note of where my ejected brass is landing. Anything over 3 feet is, generally, fine with me.
Hope this does it for ya!
