Mag tuning question (STI)

[MJinPA]

I have one 140mm mag that needs a little extra force to fully seat. Does not seem to be a spring tension issue because the issue is there where loaded to 19 or 20 (.40). The issue is less evident when empty but still there. Any ideas? Should I be looking at the mag catch or the notch in the mag? Or something else?

 

 

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[zzt]

If your other mags seat well it is not the mag catch shelf.  It may well be a spring and/or follower issue.  Remove the spring and follower and put a set from another properly functioning mag in and try it again.  If it works it was a spring and/or follower problem.  If it didn't, it's a mag body problem.

[Postal Bob]

14 hours ago, MJinPA said:

The issue is less evident when empty but still there.

That's telling me you mag body is out of specs somewhere. Remove the spring and followedr. And try inserting the mag in and out slowly while holding in the mag release. If you feel any resistance, look for rub marks on the mag body. Confirm the spot by marking with a black marker, and insert the mag several times. Then try resizing the mag body in a vice with something covering the vice jaws to protect the mag. Sometimes the mag body develop a bulge if a mag with many rounds in it is dropped onto a hard surface.

I had a brand new mag that wouldn't  insert the last 1/8". Something  was badly out of specs on the mag body. Returned it as defective and was sent a new one.

[MJinPA]

That's telling me you mag body is out of specs somewhere. Remove the spring and followedr. And try inserting the mag in and out slowly while holding in the mag release. If you feel any resistance, look for rub marks on the mag body. Confirm the spot by marking with a black marker, and insert the mag several times. Then try resizing the mag body in a vice with something covering the vice jaws to protect the mag. Sometimes the mag body develop a bulge if a mag with many rounds in it is dropped onto a hard surface.
I had a brand new mag that wouldn't  insert the last 1/8". Something  was badly out of specs on the mag body. Returned it as defective and was sent a new one.

Tried this and no resistance. Took the release out and cleaned then polished. Also made sure the channel in the grip was thoroughly clean. This seemed to help a lot. Still not perfect so something still needs to be tweaked.


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[Edge40]

Has it always been a problem with that particular mag?  If so the mag catch hole in the mag could be out of spec.  If its a new issue I also suspect the tube swelled a bit.  Adam from Atlas gunworks has some good videos on tuning mags and dealing with those kinds of problems.

[MJinPA]

Has it always been a problem with that particular mag?  If so the mag catch hole in the mag could be out of spec.  If its a new issue I also suspect the tube swelled a bit.  Adam from Atlas gunworks has some good videos on tuning mags and dealing with those kinds of problems.

It’s always been a problem with this mag.


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[Edge40]

Im thinking notch in the mag.  Check it with your mags that are known to work.

[MJinPA]

I’ll have to compare measurements tonight to see if the problem mag need to have some material removed from the catch hole.


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[Furrly]

Mag body problem.. And or mag catch slot, like others have said. 

Atlas gunworks has great mag body tunning vid on YouTube 

[mmlook]

18 hours ago, Furrly said:

Mag body problem.. And or mag catch slot, like others have said. 

Atlas gunworks has great mag body tunning vid on YouTube 

this

take the mag apart. 
blue the entire top part of the mag with a sharpie.
insert a few times, and release.
See where the sharpie rubbed off, that's where you need to adjust with either a vise or brass hammer

[Postal Bob]

Here's some relevant info that just happened to me:

 One of my mags just started having trouble seating easily. There was some resistance to going in the last 1/8-1/4". It wasn't evident until I locked the slide back, and slowly inserted the mag. The left feed lip front edge was catching the area of the slide stop removal notch on the slide. With the slide removed, it inserted fine. Over time, obviously from dropping loaded mags on a hard ground, the feed lip opened up a little. After adjusting the feed lips back to spec, and then filing a small radius to the outside edge, the mag inserted smoothly again. After this, I chamferred all the outside edges of my mag feed lips.

Hope this helps by giving you someting to look for.

[MJinPA]

Here's some relevant info that just happened to me:
 One of my mags just started having trouble seating easily. There was some resistance to going in the last 1/8-1/4". It wasn't evident until I locked the slide back, and slowly inserted the mag. The left feed lip front edge was catching the area of the slide stop removal notch on the slide. With the slide removed, it inserted fine. Over time, obviously from dropping loaded mags on a hard ground, the feed lip opened up a little. After adjusting the feed lips back to spec, and then filing a small radius to the outside edge, the mag inserted smoothly again. After this, I chamferred all the outside edges of my mag feed lips.
Hope this helps by giving you someting to look for.

Thanks! I do think it’s time to see if my mags need to be re-tuned. However, I swapped my STI release with a friends Dawson release and the mag seems to be a non issue. BUT since it was only one mag give issues with the STI release I’m sure that something is a bit off on that mag. I plan to take a close look at all.


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