Since my previous post concerning the split slide of my GSG 1911-22, I've done done a great deal of research, have communicated, both by phone and email with an ATI representative, and have discovered photo-documentation of four other incidents of the same, and worse, catastrophic failure in the GSG pistols in the exact same area of the slide.
I was informed by the ATI rep. that the slide material is "Zamak 5", and that "the material has been tested and was approved for use with the high velocity rounds." I was also told that "The manufacturer recommends Federal American Eagle but as you also stated CCI [I had indicated that some magazine reviewers had recommended CCI Stingers as being 'loved' by the GSG they had tested'] as also works very well. Now the weapon will work with Remington however it is not the recommended ammunition to use with the weapon." Remington Thunderbolts were the ammo in use when the slide split. Nowhere in the manual, or in any of the company literature I have read, has there been any mention of recommended or forbidden ammo, the only reference, in the GSG Manual, to ammo being: “...we decided to adjust the GSG-1911 to the high quality standard-ammunition as well as the HV ammunition.
I did a bit of research on the metal "Zamak 5", and found that it is a zinc alloy (commonly referred to as pot-metal) with a fatigue value roughly half that of 7075-T6 Aluminum. I'm not a metallurgical engineer, and I'm not doubting that the material was "approved for use...", however, I do have some serious doubts regarding the machined thickness of the material in the high-stress areas of the receiver where the failure is occurring.
After studying the split slide quite closely, and formulating some opinions, I took a few measurements. Some were difficult to reach with mics and calipers without dismantling the receiver—which I did not do, in order not to hinder the ATI armorer's inspection—but, as near as I could come without doing so: The rear sight dovetail groove is so deep that only .021" of material remains between the bottom of the cut and the interior broach-bottom. That is an area .450" wide, and .760" long, extending the entire length of the interior cavity. The thickness of the material along the tear—as near as I could get without springing the detached side of the slide—is about .050", with just a sliver of material .550" by the same thickness (.050") which extends all the way to the rear of the slide side where it meets the rear, top of the slide. For these extremely thin pieces of a cast metal with a fatigue rating of 85 MPa (7075-T6 Aluminum is: 159 MPa, and 4140 steel is 417 MPa, approx.) to hold up to the hammering of 50,000 rnds. of HV ammo—as has been reported by some, is absolutely miraculous. Mine failed at 500 rounds, others (those I could find online) at somewhat more, and my slide-stop has been peened completely round in those 500 rounds. This stuff is SOFT!
ATI has proven quite willing to replace the slide, and examine the frame so as to assure that it was not also damaged, and I am quite disappointed, because the GSG is otherwise a beautiful pistol, but, after reviewing all the data I could find, I have concluded that I could never again feel secure in firing this pistol, and will be purchasing either a another brand pistol—or a conversion kit for my RIA 1911/45 Match, whose slide is made of, at the very least, 7075-T6 Aluminum.
I am not bad-mouthing GSG, nor ATI, for, judging by all accounts, I believe them both to be excellent and conscientious companies. I merely feel that the characteristics that I have mentioned concerning the choice of material, and the machining of the slide in critical areas are such that make this gun potentially dangerous to the shooter. That is the only reason I have written such a lengthy post, and I would caution owners to be vigilant in inspecting for any hairline cracks forming anywhere between the top-left corner of the ejection port and the rear of the slide at the left, upper corner of the hammer opening.
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"Men fight for liberty and win it with hard knocks. Their children, brought up easy, let it slip away again, poor fools. And their grandchildren are once more slaves." D.H. Lawrence