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Posted: 11/20/2011 6:02:41 AM EDT
| My friends S&W MP15 safety stopped working. We took apart the trigger to see if we could see anything unusual and reassembled it to no avail. Any ideas? |
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Have you completely removed the fire control group? I'm thinking that either:
1) The rear end of the trigger if rounded or broken off. 2) The front part of the safety is rounded off. 3) The trigger pivot pin hole is no longer round. The above are just an educated guess. Below is a picture of how the safety works. The black semi-circle is supposed to be a cross-section view of the business end of the safety. Not much there to go wrong. 
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It's got less than 60 rounds through. Shouldn't be wear and tear. We've taken it complete apart to compare to another trigger setup and we couldn't see anything unusual. The detent and spring are all there. The disconnect or spring is also there. We even tried putting my safety switch in and that did nothing either.
Lemme know guys we appreciate it. |
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Quoted:
It's weird cause his safety was working fine till we tried changing the pistol grip. Start looking at every part you removed or replaced, at that point. If it worked before, and doesn't work afterwards, then chances are high that it's something you did. ETA: The typical parts list - what brand LPK, what brand trigger, if different than the brand of LPK, what pistol grip did you swap on, what came off, etc. Did you guys try to modify the trigger at any point, or did someone else? The devil is in the details. |
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I'll see what else I can find out about it, maybe even swap parts when we can. It's weird cause his safety was working fine till we tried changing the pistol grip. First off, can you explain TRIED Did you use a different grip screw? If you used a longer screw, it may have bent the rear of the trigger Did you put the old grip back on? |
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Quoted:
It's weird cause his safety was working fine till we tried changing the pistol grip. its either the detent/spring from the pistol grip was installed backwards or not at all when you messed with the grip, or if you used a different/longer screw to attach the new/different pistol grip. |
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Yes. We "tried" to change the grip... only to realize the store sold us the wrong grip. So the stock grip went back on. Actually, we have the grip off at the moment.
The LPK is the original that came with the S&W M&P 15. On my 16in PSA rifle, I can get my safety to work without the grip, detent and spring on. So is it really anything to do with the grip, detent or spring? |
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The spring and detent need to be in to function. The springand detent put upward pressure to engage the safety. Thus, it needs to be installed to work. My PSA has no problem engaging the safety with no grip spring and detent in. Yes I have to hold the safety trigger for it to stay on safety, but the hammer doesn't slam. edit: not saying you're wrong, it's just weird to me since I'm new to this stuff. We'll take another look at it soon. |
| Something is wrong with your trigger or selector and (it will work without the spring and detent for testing purposes). If you move the selector to safe you should not be able to pull the trigger if in safe mode and you can fire the weapon look to see if there is wear on the edge of the selector or the back on top of the trigger where the selector contacts the trigger. |
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The spring and detent need to be in to function. The springand detent put upward pressure to engage the safety. Thus, it needs to be installed to work. Needs to be installed to hold the selector in position but has nothing to do with function. All the selector does is block the back of the trigger from moving upward so detent and spring has nothing to do with the function. |
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Quoted:
Something is wrong with your trigger or selector and (it will work without the spring and detent for testing purposes). If you move the selector to safe you should not be able to pull the trigger if in safe mode and you can fire the weapon look to see if there is wear on the edge of the selector or the back on top of the trigger where the selector contacts the trigger. With the selector in safe the weapon still fires. Will look into what you've mentioned. How long does it normally take selectors and trigger contact points to go bad? This weapon has less than 100 rounds through it. |
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Quoted:
Quoted:
Something is wrong with your trigger or selector and (it will work without the spring and detent for testing purposes). If you move the selector to safe you should not be able to pull the trigger if in safe mode and you can fire the weapon look to see if there is wear on the edge of the selector or the back on top of the trigger where the selector contacts the trigger. With the selector in safe the weapon still fires. Will look into what you've mentioned. How long does it normally take selectors and trigger contact points to go bad? This weapon has less than 100 rounds through it. I've never had one fail. I think it is quite obvious that the problem has to do with what you did when you tried to replace the grip |
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doubt the safety failed, probably something came out of place.
i did a search for the sw mp 15 parts schematic, looks the same as a regular old ar 15 lower. uninstall the grip, spring and detent, and safety selector. check that the trigger group is in place, re install safety and test function. |
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Quoted:
uninstall the grip, spring and detent, and safety selector. check that the trigger group is in place, re install safety and test function. First thing we did was take the trigger apart and re install. We tried my safety selector from my weapon also. Maybe we should try my disconnector and spring to see wassup. |
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Going out on a limb here. I bought a stripped s&w lower about a year ago. When I assembled it with a DPMS LPK, everything worked fine. The safety was difficult to install, but went in after a light pop with a small(3 ounce or so) rubber mallet. After maybe one or two hundred rounds, the safety started acting as described here. Cock hammer, safety on, pull trigger, hammer falls. Turned out the safety selector holes through the lower weren't quite straight, and after a little wear the safety was loose enough for pulling the hammer to lift it upward and cause the problem.
Don't know if that's what's going on with yours, but you might look for angled or egged selector holes. |
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