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Help please - MPX K mystery spring

This is a discussion on Help please - MPX K mystery spring within the SIG Sauer Rifles forums, part of the SIG Sauer Forum category; 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 ...


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Old 09-12-2020, 10:40 AM   #1
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Help please - MPX K mystery spring

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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Old 09-12-2020, 10:58 AM   #2
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Is this where it goes?
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Old 09-12-2020, 11:05 AM   #3
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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.

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Old 09-12-2020, 11:17 AM   #4
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Is this where it goes?
My Timney #683 has a screw in that location.

Bill
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Old 09-12-2020, 11:32 AM   #5
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My Timney #683 has a screw in that location.

Bill
Thank you very much Bill. I will leave it in there for now.
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Old 09-12-2020, 12:48 PM   #6
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My Timney #683 has a screw in that location.



Bill
Mine too. I suspect that you're missing a retaining screw...

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Old 09-12-2020, 02:21 PM   #7
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Thanks again both, I am pretty sure there was no screw falling out. Will contact SIG CS Monday morning.
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Old 09-14-2020, 03:58 AM   #8
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It does not go in the trigger assembly. Looks like the firing pin spring. Your owners manual has a great breakdown of the upper and it’s parts.

If you don’t have the manual handy here is a link. Go to page 55 for where it should go.
https://www.sigsauer.com/wp-content/...016/07/MPX.pdf

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Old 09-14-2020, 12:41 PM   #9
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Is this where it goes?
SIG CS confirmed this morning that this is the disconnector spring and it does indeed drop in on top of the trigger.
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Old 09-14-2020, 07:41 PM   #10
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It appears that there should be a screw to retain the spring. Are they sending you one?

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Last edited by griff411; 09-14-2020 at 09:30 PM.
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Old 09-14-2020, 09:30 PM   #11
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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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Old 09-15-2020, 07:21 AM   #12
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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.
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Old 09-15-2020, 08:54 AM   #13
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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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Old 09-15-2020, 09:21 AM   #14
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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.

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Old 09-15-2020, 05:15 PM   #15
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Quote:
Originally Posted by MrMcGoo View Post
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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