STI Mag Issue

[Sarge]

During my gun feeding escapades I noticed something odd with my STI mags.

With my 170's i can thumb off rounds from a loaded mag and all rounds present in a nice nose up position one after the other until empty.

With all 8 of my 140's once I thumb off the first round all subsequent rounds present in a low flat manner and will not pop up to a nose up position.

To eliminate the obvious, the 140's are all within spec at feed lips and springs are good. I even bent the spring back near the top as I read worked for MBX mags. I also crammed a 13 coil spring in there and it is super tight and rounds still don't pop up.

Makes me wonder if this is normal? Again EVERY 140 I have does this

 

[Shmella]

9mm or 38SC? if 9 spacers in the mags? Are they glued in place if so?

[EEH]

Sarge, I have only four 140 Sti mags.three of them will peel off rounds with my thumb,only one will do like yours, but only for the top two rounds. All others are fine.I also run 13coil springs in my 140's

 

no my spacers are Not glued in

Edited February 24, 2017 by EEH

[Sarge]

53 minutes ago, Shmella said:

9mm or 38SC? if 9 spacers in the mags? Are they glued in place if so?

 

21 minutes ago, EEH said:

Sarge, I have only four 140 Sti mags.three of them will peel off rounds with my thumb,only one will do like yours, but only for the top two rounds. All others are fine.I also run 13coil springs in my 140's

 

no my spacers are Not glued in

Thanks guys. 9mm steel glued

[Sarge]

For clarity

170

 

 

140

 

[Shmella]

Just a thought, try to do this and see if it makes any difference.  Try to push the round to the very edge of the feed lip right before it pops out. Very slowly, once it is barely hanging on to the end of the feed lip quickly push the round out the rest of the way instead of slowly pushing the round out from all the way back like you did in the video. The way Im describing(or trying to describe) will better simulate a round being stripped off quickly just like it would during firing and the remaining rounds should pop up (hopefully) like they would if you fired the rounds out of the gun.

[Sarge]

39 minutes ago, Shmella said:

Just a thought, try to do this and see if it makes any difference.  Try to push the round to the very edge of the feed lip right before it pops out. Very slowly, once it is barely hanging on to the end of the feed lip quickly push the round out the rest of the way instead of slowly pushing the round out from all the way back like you did in the video. The way Im describing(or trying to describe) will better simulate a round being stripped off quickly just like it would during firing and the remaining rounds should pop up (hopefully) like they would if you fired the rounds out of the gun.

That does make them pop up.

[Shmella]

2 hours ago, Sarge said:

That does make them pop up.

So I dont remember where I heard it but I remember seeing somewhere that way of stripping the rounds is how you should check to see if your feed lips are tuned correctly. 

[Glk21C]

Sarge, the control rib on either side of the mag that is in the double-stack to single stack transition area have always been too wide or have gotten out too wide from use (usually from dropping them with rounds inside, like we all do upon live fire reloading).  Your 170 mags are within spec as they are presenting nicely.

 

You have to squeeze them tighter WITHOUT getting the mag out of square AND without causing the top single stack area under the feed lips to get too narrow.  You also have to squeeze them more than you think you should as the metal will spring back some when the clamp pressure is removed.  Those control ribs are what control the presentation of the rounds.

 

There is a tutorial about this concept on here somewhere by Jim Anglin and another by someone else, has to do with Caspian mags but the theory is still the same.

 

Good luck

[Sarge]

40 minutes ago, Glk21C said:

Sarge, the control rib on either side of the mag that is in the double-stack to single stack transition area have always been too wide or have gotten out too wide from use (usually from dropping them with rounds inside, like we all do upon live fire reloading).  Your 170 mags are within spec as they are presenting nicely.

 

You have to squeeze them tighter WITHOUT getting the mag out of square AND without causing the top single stack area under the feed lips to get too narrow.  You also have to squeeze them more than you think you should as the metal will spring back some when the clamp pressure is removed.  Those control ribs are what control the presentation of the rounds.

 

There is a tutorial about this concept on here somewhere by Jim Anglin and another by someone else, has to do with Caspian mags but the theory is still the same.

 

Good luck

Thanks. I'll do some research.

[Shmella]

19 hours ago, Sarge said:

Thanks. I'll do some research.

Just checked my 140 sti mags and they do the same thing yours do. I've ran them in two open guns and a limited 9 and have never had a ftf with them. I just loaded them to capacity and will be running them in practice today again. I also tuned them myself per Dawson's instructions with their kit. I've put 800 rds through my new open gun so far with these mags without issue. Something tells me the mags aren't your feeding issue but you can never be too safe I guess when it comes to wanting to eliminate all possibilities. Im going to continue to use these how they are until the give me a reason to mess with them more. Good luck. 

[Sarge]

5 minutes ago, Shmella said:

Just checked my 140 sti mags and they do the same thing yours do. I've ran them in two open guns and a limited 9 and have never had a ftf with them. I just loaded them to capacity and will be running them in practice today again. I also tuned them myself per Dawson's instructions with their kit. I've put 800 rds through my new open gun so far with these mags without issue. Something tells me the mags aren't your feeding issue but you can never be too safe I guess when it comes to wanting to eliminate all possibilities. Im going to continue to use these how they are until the give me a reason to mess with them more. Good luck. 

Yeah. And as I said before they all run great in my other gun. Still looking for a Dawson or STI mag catch to try. I swapped the mag catch from my gun with ftf issues to my other gun and that caused problems there as well. But I still had one ftf out of 200 rounds with STI mag catch in problem gun. I think I'm getting close. lol