So I purchased 3 more springs to do 3 more of my kci magazines that were having issues and these springs are the truth. No more fail to feeds. My kci .40 mags are completely reliable now. Going to slowly start swapping my springs out of my other kci .40 mags over the next year that havent been done. They feed reliable in two different .40 Glocks and two different carbines. Thanks glockmeister. So far between 6 magazines and roughly 1300 rounds, not one failure do to feeding. My original post was jan2018 and this post is 8Feb2018. All firing has been indoor range and 3 of 6 magazines was fully loaded for about two weeks before taking out. Others were loaded at range. You can get about 29 rounds in for first 3 loads and now can take full 31.
Great fix for kci .40 mags
Not sure if these was the ones I was supposed to use in the .40 31rd mag, but I did. These replaced the stock springs in my kci 31rd .40 mags and the mags have performed flawless since. I feed a Glock 22 and a keltec sub 2k and have not had one issue since swapped out today. Got the springs today, installed them into my mags, and shot them today at indoor range with no more ftf issues. Put 427 rounds threw 3 mags that was spring swapped. Also brought a fourth magazine without spring change for comparison and it fail 9 times out of 66rds. So I know the springs was the difference in reliability. Just spring swap to mags. Nothing else. They was having ftf issues prior to today every time out over last 3 months since getting them. Very happy. These got to me fast and work flawless. Super happy customer.