first check and ensure that your firearm is unloaded. field stripping disassembly and assembly my smith&wesson M&P 9mm using my powershot G7 digicam. double action only semi-automatic pistol other features include ambidextrous magazine release and slide lock, front rails, fish scales serrated slide with 3 sizes changeable back straps and 2 x 17 rounds magazines. make sure when you replace back your barrel, recoil spring should snugly fit its groove perfectly staight and aligned to avoid premature take up of spring while pulling your slide back causing take down lever to flip halfway. you would not need to hold back your take down lever with index finger blocking it just bring the slide fully rearward briskly with no hesitation and takedown lever will return by itself...if not, then simply release it.
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