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Discussion Starter #1
While cleaning my MPX K I held the lower upside down and tapped it to drop some dirt out. This spring dropped, not sure from where. It is 5/8” long and about 3/16” in diameter, it is pretty stiff. Trigger, bolt catch, mag release, everything seems to function. Can not find a schematic online.
Any suggestions will be appreciated.
 

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This is not the first loose spring found in the lower of a newer MPX or MCX. It looks like it might be a magazine catch spring though.

If everything works as it should, I would not worry about it. There isn't really any reason to find a place to put it if everything works. I would check out whether the firing pin spring is in place though by seeing if the firing pin moves back as pressure is let off of the FP.

Bill
 

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Discussion Starter #7
Thanks again both, I am pretty sure there was no screw falling out. Will contact SIG CS Monday morning.
 

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SIG CS confirmed this morning that this is the disconnector spring and it does indeed drop in on top of the trigger.
You need to take the spring out and then do a function check of the disconnector per the manual without live ammo. I suspect that the disconnector will work properly without that spring.

A loose spring could tie up your MPX. Disconnector springs are always securely held in place to prevent uncontrolled full auto fire.

Bill
 

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Discussion Starter #12
Thank you for the additional comments. SIG CS did not mention anything about a screw to retain the spring. Will double check with them.
 

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Thank you for the additional comments. SIG CS did not mention anything about a screw to retain the spring. Will double check with them.
Do the function test per the manual without the spring in place.. The CS rep may think that you have a mil-spec trigger or that a Timney works like a mil-spec trigger.

What is at the bottom of the hole is a screw holding a nylock dowl in place. The nylock keeps the hex screws on either side from backing out and loosening the trigger's tension on the trigger pins.

Many SIG CS reps don't know much about the MPX or Timney triggers. If you want an expert on Timney triggers, you'll have to call Timney. Be sure to tell them you have a 683 in your SIG and NOT the 681. SIG made Timney redesign their trigger for the MPX due to the beating the MPX hands out.

Bill
 

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To help eliminate other possibilities, I'd also check to see if the firing pin spring is in place. That was actually my first thought when I saw the photo.

Sent from my moto g(6) using Tapatalk
 

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Discussion Starter #15
Do the function test per the manual without the spring in place.. The CS rep may think that you have a mil-spec trigger or that a Timney works like a mil-spec trigger.

What is at the bottom of the hole is a screw holding a nylock dowl in place. The nylock keeps the hex screws on either side from backing out and loosening the trigger's tension on the trigger pins.

Many SIG CS reps don't know much about the MPX or Timney triggers. If you want an expert on Timney triggers, you'll have to call Timney. Be sure to tell them you have a 683 in your SIG and NOT the 681. SIG made Timney redesign their trigger for the MPX due to the beating the MPX hands out.

Bill
Great suggestion, thank you Bill. SIG CS confirmed that there is no screw to retain that spring. Will reach out to Timney and will post any further information I get
 

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Discussion Starter #16
To help eliminate other possibilities, I'd also check to see if the firing pin spring is in place. That was actually my first thought when I saw the photo.

Sent from my moto g(6) using Tapatalk
thanks griff 411. firing pin spring was in its place when I disassembled the bolt carriage group
 

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Great suggestion, thank you Bill. SIG CS confirmed that there is no screw to retain that spring. Will reach out to Timney and will post any further information I get
For reference, here is the Timney trigger group in my MPX-K. It may be hard to see, but there is a hex screw visible. I believe that I'm seeing female threads in the same location on your gun.


Sent from my moto g(6) using Tapatalk
 

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Discussion Starter #18
Another call to SIG CS confirmed that a set screw is required to hold the disconnector spring in. They cannot sell me the screw, I have either have to send the MPX in to have it repaired or try to get the screw directly from Timney.

Has anyone had any luck getting through to Timney? They never answer the phone, I have been leaving messages since last week, raised a request online to which a service number was assigned, to no avail.

Would rather not have to send it in and wait for a couple of weeks to have a screw put in.
 
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