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Non-Captured Guide Rod


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Short Version: The metal guide rod I'm using has a screw and a small cap to capture flat springs, but regular wire spring just slides past it. My best guess is that I just take out the screw and use the wire spring like I would in any other gun. But I have a few questions, it's a Gen-3 G34 foofooed by TTI a few years back. 

  • Is there any known reliability issue with the non-captured setup, e.g., that the spring and rod interact in some way to snag from time to time? 
  • Should I remove the screw or keep it? There is a minimal length difference with and without, but it also makes the tip smooth(er). 
  • Should I add a washer and use the existing screw at the tip of the rod to create a captured spring instead of non-captured? 
  • Besides being easier to field strip, are there any other considerations between captured and non-captured setups? 

 

Long Version: A few years back, just for fun, I got a Gen-3 G34 specifically so that I could send it to TTI for one of their "movie upgrades." The gun came back looking and shooting great, as expected. It's my only full size Glock - I only have a few Glocks and I don't use them in competition so I am not too familiar with more advanced details. 

 

Some time later, while shooting some random local matches I figured it would be fun to have it set up for C/O so I got an aftermarket slide from Brownell's that was pre-cut for optics (in CA we have all sorts of limits, so getting a pre-cut slide is a great shortcut). After adding some cerakote finish to the slide and mounting optics, the C/O gun was ready for the show. Or so I thought. It would stove pipe half the time and the other half it would have a FTF where the slide "outruns" the round from the magazine. If it was stock, I would immediately look at  the recoil spring, but this is a non-OEM slide on heavily modified frame with some additional finish(es). It wasn't a high priority at the time, so just as I was about to dedicate time to look into the problem, Covid struck and then everything was on hold for a period of time.

 

As the ammo (and primers) are getting back in stock, I had some time to get back to this problem and fix it once and for all. I brought along different ammo, reloads and some factory loads, I had others at the range fire the gun, tried different magazines (metal MBX and standard polymers, both CA and free state), etc. As the last step before I borrowed someone else's frame to test the slide (non-OEM on non-OEM setup), I ordered a spring calibration pack from Wolff. That's when I realized for the first time that the Glock spring assembly is somewhat peculiar with the captured spring (I simply never paid attention to it). Turned out I had three recoil springs lying around, the original plastic that came back after TTI upgrades, the metal one from TTI and (likely) a heavier one that I purchased who knows when. After looking up on the web how it works, I felt I would break the plastic one if I tried to remove the cap, but the extra metal one was perfect for my needs - I could compress the spring, hold the rod with vice-grips and then unscrew the top screw (which had something similar to purple Loctite to keep the screw in place).

 

The plan to diagnose the problem was easy - go to the range with the assortment of springs, use vice-grips and hex key to change them on the fly. If the problem remains, escalate - get a friend or two with stock frames and slides, then start crisscrossing setups and determine whether it's the frame or the slide causing the issues. As I was about to set up the first spring, I put it on the guide rod, compressed it, held it with vice-grips in place, put the screw on, released it slowly and it happily slid over the screw undeterred. Ugh!

 

Frustrating as it can be, before I chucked everything in frustration, I took a look at the design and for the first time noticed that the springs were different. The flat spring not only had a different look, but it was narrower at the end so it could be retained. Doh! Then I looked at how the spring is held in the front of the slide and noticed there is no cup of any kind (like on a 1911/2011), it just rests flat against the slide. But, the guide rod goes through the little hole, so that should hold both the spring and the rod in place if I could squeeze it together and put the slide back on. Sure enough, after a few attempts I was able to find a way to guide the rod through the hole, put the slide on and confirm that it appeared to cycle fine. Well, turns out this is quite a standard setup, it was just new and unknown to me, which I found out after getting home and doing an online search. But I didn't find the fine details about using non-captured springs, hence my question above in this thread. 

 

And yes, the spring fixed the problem. It needed a #14 spring to cycle normally. Heavy springs cause slide to go forward prematurely, riding the round in the magazine instead of pushing it forward. And it's likely the same with stovepipes, where the slide doesn't have enough speed or even doesn't go all the way back so the ejector can't do its job. Looking back, it's obvious that a heavier setup with optics on top requires lighter, not heavier spring (which is the first setup I tried, just to be sure/safe). The heavier slide will move slower using the same ammo, even if it is true that a heavier spring would be required if the heavier slide moved at the same speed as the lighter slide. Well, it doesn't. Yet under DOH! Live an learn... 

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