yosturm

STI 2011 magazine feeding issue

14 posts in this topic

One of my four STI mags consistently fails to feed in the manner as seen in the photo.  This magazine does so about every 4 rounds.  The magazine has stock STI internals, as do all of my other magazines which function fine.

 

I have the Dawson Precision mag adjustment kit and have "tuned" this magazine as per the instructions on the video.  The critical dimensions of this magazine are within the acceptable specs.  I measure about 1.352 at the back of the lips to 1.360 at the front.  My three other magazines which all feed fine have varying dimensions, some a little bigger, some a little smaller, so I can't figure out why this one magazine is having issues and none of the others.

 

All other surfaces look normal when compared to the other magazines.  Any suggestions?

IMG_00431.jpg

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You have to put grams springs and followers in them.

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But the other three work just fine?  I will swap springs/followers around to ensure that it is this magazine tube and not some combination of springs/followers.

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Do all mags sit at the same height when inserted?

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I agree go with grams guts. Test the bad guts in another mag

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Taran guts work well also.  Is this mag your most used mag?  Is the case not getting underneath the extractor?  Take the spring and follower out of a working mag and test.  The spring could be weak if its your most used mag.  

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I would check your extractor for the following: 1) tension should be just enough to hold the round in place on the breech face (check this with the slide removed from the frame and the barrel removed from the slide), 2) the extractor hook should not be touching anywhere in the beveled portion of the case (the only be contact from recess cut on the extractor and the case rim), and 3) the flat where the case rim rides up on the extractor should be bevelled on the bottom.  

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Thanks for the replies.

 

I checked and it does not sit any higher then the rest of the magazines which function fine.

 

I have swapped the internals with another one and will have to have another range day soon to test that theory.  Magazines are all relatively new.

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22 hours ago, ltdmstr said:

I would check your extractor for the following: 1) tension should be just enough to hold the round in place on the breech face (check this with the slide removed from the frame and the barrel removed from the slide), 2) the extractor hook should not be touching anywhere in the beveled portion of the case (the only be contact from recess cut on the extractor and the case rim), and 3) the flat where the case rim rides up on the extractor should be bevelled on the bottom.  

 

Here's your problem. Your extractor is not allowing the loaded round to come up underneath. I solved it by installing an Aftec.

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With no prior information, I would look at this photo and suspect your extractor as well. With either dummy rounds that are the same length as your match ammo or your match ammo with a shortened firing pin, I would insert each mag and and hand cycle some rounds through your gun.  If they feel chunky, then I would recommend tuning your extractor.  If they all feel smooth, then I would try changing out the springs and/or followers as others have mentioned.

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7 hours ago, MikieM said:

 

Here's your problem. Your extractor is not allowing the loaded round to come up underneath. I solved it by installing an Aftec.

 

But could that be the case if all of the other magazines have 0 malfunctions and only this one does?

 

Either way, I will hit the range this weekend and test the swapped magazine internals to see how that works.

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Posted (edited)

52 minutes ago, yosturm said:

 

But could that be the case if all of the other magazines have 0 malfunctions and only this one does?

 

Either way, I will hit the range this weekend and test the swapped magazine internals to see how that works.

 

What I said isn't etched in stone. The change in extractors worked for me.

If that one mag is the only one with malfunctions then I would certainly look at it first. Check the dimensions. Adam, at Atlas Gun Works, has some good videos on YouTube about tuning magazines.

Load ten, or more, rounds into the mag. With the magazine in the gun note that the first round should (ideally) be pointed at the center of the chamber. The first round should (again ideally) be sitting flat against the second round in the mag. This will occur when the mag feed lips are set correctly.

Check the dimensions of the bad mag against the good ones. Take the spring out and make sure the bottom of the follower is not cocked one way or the other, and that there are no twists in the spring. A weak spring usually causes nose dives, and a twisted spring will act like a weak spring.

When everything is back to where it should be, load the magazine fully and let it stand in a dark corner for a few days. New mag springs are like ex-wives. They have good memories.

Good luck.  :D

Edited by MikieM

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22 hours ago, MikieM said:

 

Here's your problem. Your extractor is not allowing the loaded round to come up underneath. I solved it by installing an Aftec.

 

Aftec is a good choice.  But they are not a drop in part.  They still need to be checked and tuned for the same three things I listed.

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49 minutes ago, ltdmstr said:

 

Aftec is a good choice.  But they are not a drop in part.  They still need to be checked and tuned for the same three things I listed.

 

You're absolutely right.

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