I recently acquired a used Glock 36. It was very dirty, but cleaned up well. First day at the range it functioned OK with many different loads except for one failure to extract out of about 150 rounds. Noticed that none of the 4 used mags (square notch) drop free. My questions: 1. is it recommended that all/most springs be replaced right away because of the unknown history of the gun? 2. should the mags drop free, and if not, what should be done?