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Discussion Starter #1
I bought my pistol used, an M&P 40(version 1). When I got it home I took it apart to clean and look at and noticed, inside the trigger return spring, there was a fabric material inside. I thought it was compacted lint, that was missed whenever it was cleaned by whoever took them in as Police trade ins. I bought a MCarbo spring kit to try in it and noticed that the supplied spring also has that material in it. So, I'm assuming it serves some purpose. I've never seen this before in any of the other firearms I own.

Can someone explain it to me?

Thanks,
John
 

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It acts as a harmonic dampener for the spring. Many racing engines e.g. NASCAR, use the conical style valve springs for the same reason.

Screen Shot 2020-06-07 at 5.36.47 PM.png


Photos by permission: Anatomy Series of Manuals M&P Full Size
Caution: Pseudo-science and / or amateur photos may be embedded in this post.
 

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Discussion Starter #3
Thank you very much for that. I greatly appreciate it. This is the first time in my life I've encountered that. Glad I didn't dig it out now.

Also, looking at that image, I need to go back into my pistol and reposition the spring. I have the back coil loop going through the hole and UNDER the transfer bar. I guess I need to flip it up so the coil goes over the top of the transfer bar. Just in case the spring angle may make a difference in things.
 

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The spring coil in the "up" position is a positive engagement when the trigger is pulled, i.e. it becomes more secure. When in the down position it is a negative engagement and might become dislodged with trigger movement.
 

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Discussion Starter #5
Ok. Thanks. Good to know. I like having a better understanding of the dynamics of how the parts work together.
I've always liked knowing how things work. As a kid, I not only took apart all my toys, I actually put some.of them back together. Its followed me through my 50 years and hasn't stopped.
 
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