This article is somewhat related to an earlier one I wrote on Open Gun reliability. Granted, I am not the best shot, but you cannot expect to make vast performance improvements without equipment that is 100% reliable.So far, for me, it was extraction issues, which were eliminated by replacing the standard extractor with an Aftec; which meant goodbye to smoke stacking.
Now we are dealing with double feeds. This is when two live rounds are attempting to chamber at the same time. It is a common STI magazine problem, particularly with 9mm Major. The issue revolves around the magazine feed lips. They are usually too far apart, so the round isn't effectively held in position.
I use 140mm magazines, which are high capacity, which compounds the problem. The magazines have to be limited to 10 rounds (Canada), and arrive from the supplier with this primitive plate rivetted in. This plate causes a huge amount of problems. For starters, these things look like they have been cut by a hand saw. Each plate varies in length. The net effect is that, ceteris parabis, when you try to seat the magazine in the gun, those with slightly longer plates make it impossible to seat. You need a little bit of give in the spring to allow this to happen. I initially overcame this by replacing the cheap basepads with sturdier alumium ones. This provided a little more space, which loosened up the spring. But this advantage was short-lived. Another issue with the plates is that the rivets catch on the magazine spring, resulting in feeding issues. A final problem is that you cannot remove the spring and follower, since the plate blocks this process; so cleaning your magazines is a non-starter. Overall the rivetted plate is a bad idea; especially in magazines costing around $75.00 a piece.
Once I started experiencing double feeds I realised that I needed to tune the magazine feed lips. This involves using a caliper to measure the gap between the feed lips, and to adjust inwards/outwards using a combination of brass hammer and/or pliers. The trick is finding the correct measurements for your caliber, and then tweaking the lips to perfection. For me, solving one problem created new problems. I needed to tighten up the tolerances. This meant that the rounds would be tighter, but because of the plates, it meant that tighter tolerances removed the advantage I achieved with the new basepads. So I ended up with some magazines not seating in the gun again.
I then ordered Arrendondo Lim10 inserts, and decided I would remove all of the plates. I removed two, and tested. Voila, the magazines seated properly and didn't experience and double feeds. But the inserts are for 38 Super, so you have to "tune" them to make space for the spacer and spring. Also, because the dimensions of each magazine are not quite the same, you may need to file the tops of the inserts until you get 10 rounds to fit comfortably. Another big problem is the DAA basepads with the Arrendondo inserts. I really struggled to get the basepads to slide over the inserts. In the end I drilled a small hole in the basepads, and I push the insert down, using a thin allen key. Then the basepads slide on easily. I then went off to the range and tested all my magazines, which seemed to be working fine.
But alas, it takes a match to prove you wrong. Straight away my double feed issues were back. So now, out of desperation, I have ordered the Dawson Magazine Precision kit.
So all up, the magazines will have cost me $130.00 per unit, excluding all the time and effort to get them right. You might ask why I persist. Well, you just have to shoot an STI that is performing well, to be hooked.
I use 140mm magazines, which are high capacity, which compounds the problem. The magazines have to be limited to 10 rounds (Canada), and arrive from the supplier with this primitive plate rivetted in. This plate causes a huge amount of problems. For starters, these things look like they have been cut by a hand saw. Each plate varies in length. The net effect is that, ceteris parabis, when you try to seat the magazine in the gun, those with slightly longer plates make it impossible to seat. You need a little bit of give in the spring to allow this to happen. I initially overcame this by replacing the cheap basepads with sturdier alumium ones. This provided a little more space, which loosened up the spring. But this advantage was short-lived. Another issue with the plates is that the rivets catch on the magazine spring, resulting in feeding issues. A final problem is that you cannot remove the spring and follower, since the plate blocks this process; so cleaning your magazines is a non-starter. Overall the rivetted plate is a bad idea; especially in magazines costing around $75.00 a piece.
Once I started experiencing double feeds I realised that I needed to tune the magazine feed lips. This involves using a caliper to measure the gap between the feed lips, and to adjust inwards/outwards using a combination of brass hammer and/or pliers. The trick is finding the correct measurements for your caliber, and then tweaking the lips to perfection. For me, solving one problem created new problems. I needed to tighten up the tolerances. This meant that the rounds would be tighter, but because of the plates, it meant that tighter tolerances removed the advantage I achieved with the new basepads. So I ended up with some magazines not seating in the gun again.
I then ordered Arrendondo Lim10 inserts, and decided I would remove all of the plates. I removed two, and tested. Voila, the magazines seated properly and didn't experience and double feeds. But the inserts are for 38 Super, so you have to "tune" them to make space for the spacer and spring. Also, because the dimensions of each magazine are not quite the same, you may need to file the tops of the inserts until you get 10 rounds to fit comfortably. Another big problem is the DAA basepads with the Arrendondo inserts. I really struggled to get the basepads to slide over the inserts. In the end I drilled a small hole in the basepads, and I push the insert down, using a thin allen key. Then the basepads slide on easily. I then went off to the range and tested all my magazines, which seemed to be working fine.
But alas, it takes a match to prove you wrong. Straight away my double feed issues were back. So now, out of desperation, I have ordered the Dawson Magazine Precision kit.
So all up, the magazines will have cost me $130.00 per unit, excluding all the time and effort to get them right. You might ask why I persist. Well, you just have to shoot an STI that is performing well, to be hooked.
Wow - that is one expensive magazine.
ReplyDeleteI guess I won't complain about the $50 CZ magazines anymore.
fantastic informtion, I have the same problems and many elas.
ReplyDeleteCZ checkmate is the best "no problems at all, they fixed all issues like these"
nay way thanks a lot.
It strikes me that STI Magazine should really come WITH the Dawson Precision STI Mag Tuning kit. The DVD and mag mandrel alone are worth the expense!!!
ReplyDelete