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I have a Sig X5 that I bought a new top end for because I want the sights along with the dot.

 

My question is this, with the new top end installed when I slowly pull the trigger I notice a vertical movement at the rear of the slide.

 

When I put the original top end back on there is no movement.

 

I don't know if this is a big deal or not, but it is curious.

 

Any thoughts?

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With a striker fired pistol, at least my Glocks, if the slide starts moving with the trigger it usually means that the striker spring is not balanced with the recoil spring.  If the striker spring is heavier than the recoil spring it tends to try to take the slide out of battery when pulling the trigger.

When I use my S&W M&P 45 2.0 with light loads and a light recoil spring and a stock striker spring, it does that too.  

 

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Your new top end is just loose on the frame. The vertical movement is just the “sear” pushing up and down on the vertical face of the striker when you pull/release the trigger. 

Put a loaded mag in and you’ll notice to movement stops (top round pushing up on the slide and taking out the slack of the loose fit). 

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23 minutes ago, Gary Stevens said:

Wow, two great ideas. 

 

Thanks

 

Common in striker fired guns. 

Try it with a few Glocks (with no mag in) and you’ll see the same. 

 

A lot of 320s/X5s just have more play, so it’s more apparent. 

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2 hours ago, Ssanders224 said:

Your new top end is just loose on the frame. The vertical movement is just the “sear” pushing up and down on the vertical face of the striker when you pull/release the trigger. 

Put a loaded mag in and you’ll notice to movement stops (top round pushing up on the slide and taking out the slack of the loose fit). 

yep, only proper way to check the trigger etc.

They aren't hand fitted that's for sure!!!!

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Posted (edited)
9 hours ago, pskys2 said:

With a striker fired pistol, at least my Glocks, if the slide starts moving with the trigger it usually means that the striker spring is not balanced with the recoil spring.  If the striker spring is heavier than the recoil spring it tends to try to take the slide out of battery when pulling the trigger.

When I use my S&W M&P 45 2.0 with light loads and a light recoil spring and a stock striker spring, it does that too.  

 

 

This has nothing to do with vertical movement the OP asked about; what you describe is a totally different thing, and it's pretty specific to Glocks anyway with their partial double action trigger.

That vertical movement the OP asked about is just a result of loose slide/frame fit and the sear pulling away from the striker. 

Edited by Yondering

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9 hours ago, Yondering said:

 

This has nothing to do with vertical movement the OP asked about; what you describe is a totally different thing, and it's pretty specific to Glocks anyway with their partial double action trigger.

That vertical movement the OP asked about is just a result of loose slide/frame fit and the sear pulling away from the striker. 

Not really my S&W M&P 2.0 45 does the same thing under the same circumstances.  But I have NO experience with SIG's so you may be correct with them.

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31 minutes ago, pskys2 said:

Not really my S&W M&P 2.0 45 does the same thing under the same circumstances.  

 

What the OP is referring to is not what you are describing (or you don't really understand why your slide it moving vertically). 

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25 minutes ago, Ssanders224 said:

 

What the OP is referring to is not what you are describing (or you don't really understand why your slide it moving vertically). 

I agree I may not be accurately diagnosing the OP,  but I did not diagnose just offered suggested causes, I know what my gun did and solved the issue quite easily by balancing spring rates.

Maybe my perception of true degrees of horizontal vs vertical displacement can be more accurately refined?

And yes most of the movement is horizantal, but my point is slide movement with a Glock or S&W M&P  striker fired trigger "can", not "must", be affected by spring rates.  

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My M&P 2.0 CO gun had a visible shift left when the striker released.  I think the M&P's have a different set of issues than what the OP and Sanders are describing.

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On 7/14/2019 at 3:41 PM, Ssanders224 said:

Your new top end is just loose on the frame. The vertical movement is just the “sear” pushing up and down on the vertical face of the striker when you pull/release the trigger. 

Put a loaded mag in and you’ll notice to movement stops (top round pushing up on the slide and taking out the slack of the loose fit). 

Nailed it.

When I shoot the gun off the bench testing loads I always know when the last round has been striped out of the mag ...the red dot will shift up at the start of the trigger press. 

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