Good spring
So far so good, has maintained acceptable spring tension on the S&W M&P 17 rd factory mag with 6 rd. Extension. I kept it fully loaded for a week so far and all is well. I will update if spring fails prematurely. Should last at least 2-3 years if I leave it loaded with up to 21 of its 23 capacity. TTI Rep: We do not recommend leaving your magazines fully loaded for extended amounts of time when not in use. If you take any spring or piece of metal and fold it in half it will spring back but not to its original state. Now you go and bend the piece of metal and leave pressure on it for a long period of time that metal will not go back to its original state. We know that the springs have a better memory then a piece of metal but in time and with added pressure the results will be the same. On all my carry guns, if I keep them loaded 24/7, I rotate out the magazines and give others time to rest. I recommend everyone check their carry magazines regularly and not sure trust it to work 2-3 years down the road when they have not been properly maintained over the years. I have been using the same TTI magazine springs in my 43+2 for 2.5-3 years but I shoot the firearm regularly and rotate out my carry magazines to give the springs a break. With the proper care they will last for years. But just leaving them loaded and forgetting about them for 2-3 years I would have my concerns. Unloaded magazines springs will last forever as long as they are not stored in a humid environment. LT