Due to the different steels used and the different configurations (flat vs braided, etc), I never put a lot of stock in spring length...
That's why I always measure a new spring when I install it the first time.
From the ISMI site;
"The recoil spring should be changed, at the latest, when it has lost 0.500” of free length from new. At this point, the spring has suffered a considerable reduction in load* exerted at installed (when the gun is in battery)."
* 22.7%
ISMI Gunsprings, Made in the U.S.A.
Dave put it best, When the
premium replacement part is $8 why are you even asking the question? If in doubt, change the damn thing!
If you are not using ISMI springs in your autoloader you have either spent the last five years in a coma or you're just stuck on stupid!
Its the only recoil spring with a one year
TOTAL warranty.
Again, from the ISMI site;
"12 Month Replacement Warranty extends beyond just materials and workmanship. We even cover failure due to wear."
Do yourself a favor and go to the site and read. Still not convinced? Dial (765)565-6108 and ask for Marc Cosat and let him tell you why you should be running ISMI,
“The World’s Finest Gun Springs” in your gun.