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SF1911

Trigger/upper malfunction

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The carbine has a Hyperfire 24C trigger, Taccom upper, and a Stern lower conversion kit, with a Taccom recoil spring and buffer.. The malfunction is a intermittent (but fails often) fail to eject (empty stays in the chamber area. The change that fixed this is putting the heavier springs in the Hyperfire 24C . Works great now.  Why is this?  What do these springs in the trigger have to do with a FE problem? I'm Baffled.

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Maybe the heavier springs are helping the bolt open slower allowing the extractor a better grip. You might consider checking the extractor/spring. Maybe replace one or both.

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I had problems with failure to eject with the Stern mag block until I realized I had to adjust the big screw of the mag block to tighten up the mag block fit.  And no, I don't mean the two screws capped with plastic.

 

See this video from Stern Defense:

    

 

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The hiperfire springs should have no effect on the ejection of your round.  All the springs do is change the trigger pull.  I would suspect it's something with the ejector.  You might need to bend it slightly.

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19 hours ago, SF1911 said:

The carbine has a Hyperfire 24C trigger, Taccom upper, and a Stern lower conversion kit, with a Taccom recoil spring and buffer.. The malfunction is a intermittent (but fails often) fail to eject (empty stays in the chamber area. The change that fixed this is putting the heavier springs in the Hyperfire 24C . Works great now.  Why is this?  What do these springs in the trigger have to do with a FE problem? I'm Baffled.

Are you having a Failure to Extract OR Failure to Eject?  What do you mean by "chamber area?"  In the chamber or floating in the action?

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3 hours ago, stick said:

The hiperfire springs should have no effect on the ejection of your round.  All the springs do is change the trigger pull.  I would suspect it's something with the ejector.  You might need to bend it slightly.

Those springs compress as the hammer comes back.  Heavier springs can slow the bolt.

 

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The empty isn't in the chamber, its extracted but isn't ejected. Its sitting  between the bolt face and the chamber. I t then causes a FF malfunction. Adjusting the ejector didn't fix it. But changing the trigger springs did.

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As others have indicated, the bolt is opening too rapidly. Heavier hammer spring increases drag on bolt, slowing it down enough for proper extraction and ejection.

 

Extractor has to hold the brass well enough to drag it into ejector. Premature bolt opening might start extraction before brass is released from chamber wall. Brass then slips off the extractor before it hits ejector. Symptoms are very similar for a broken extractor nose. That’s a reason to closely inspect under good light and with some magnification. 

 

Extractor and spring are are worth looking at. 

 

Heavier buffer would probably help slow the cycle  too. 

 

Then you can go back to lighter trigger springs. 

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3 hours ago, practical_man said:

As others have indicated, the bolt is opening too rapidly. Heavier hammer spring increases drag on bolt, slowing it down enough for proper extraction and ejection.

 

Extractor has to hold the brass well enough to drag it into ejector. Premature bolt opening might start extraction before brass is released from chamber wall. Brass then slips off the extractor before it hits ejector. Symptoms are very similar for a broken extractor nose. That’s a reason to closely inspect under good light and with some magnification. 

 

Extractor and spring are are worth looking at. 

 

Heavier buffer would probably help slow the cycle  too. 

 

Then you can go back to lighter trigger springs. 

I'm thinking you and 3gunnuts are most likely correct. I'll need to do a bit of experimenting. Thanks.

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On 8/3/2018 at 1:13 PM, SF1911 said:

The empty isn't in the chamber, its extracted but isn't ejected. Its sitting  between the bolt face and the chamber. I t then causes a FF malfunction. Adjusting the ejector didn't fix it. But changing the trigger springs did.

FWIW that's an exact description of the problem I had.  Again, tightening the screw in the mag adapter fixed it.

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3 hours ago, STIboy said:

FWIW that's an exact description of the problem I had.  Again, tightening the screw in the mag adapter fixed it.

I'll definitely be looking at that screw and the tightness of the adapter also. 

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On 8/4/2018 at 9:52 PM, STIboy said:

FWIW that's an exact description of the problem I had.  Again, tightening the screw in the mag adapter fixed it.

 

A couple of extra data points:

I just returned from the range where I tested out a PCC built up from an AR15, a Stern Defense mag adapter, a TacCom upper, and an MBX recoil buffer.  I was able reproduce the prior symptoms  (brass failed to extract and hung up in the action) several other ways.

  - I switched the MBX buffer from long stroke to short stroke configuration, lightest internal spring, and the problem cropped up.

  - I returned the buffer to long stroke configuration, and switched to the strongest (red) internal spring.

 

I was using a fairly light powder/bullet pairing, probably around 130 PF.  The exact results might not duplicate what would happen with a heavier round.

 

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