So, let's talk tolerance stacking.
First, the sights are on. They finally arrived after 3 fed ex delays. I ordered stuff from the same place 3 days later and that order arrived 5 days earlier.
As I said above, I've done a lot of owner gun mod, assembled my own 10/22, ar15s, ar10s, Ruger mk2, and mk3 guns, 1911s. This isn't exactly new for me. Yet, these two, specifically the full-sized G17, and to a lesser degree, the compact g19 guns, have taught me a lot.
Before I get to what I've learned and how I've dealt with it, here are the two 17-round groups with these two at 30ft.
Gun 1, is more on point, with its group being more spread out. I'll talk more about this in a moment.
Gun 2, a tighter group and fewer issues, I installed the sights a bit too far one way. (I've made adjustments after coming back inside.)
Now on to tolerance stacking. I specked out these guns to be cheap. I'm into these for about 380 shipped, give or take a few cents. So, all these parts were not the cheapest I could find, but the most accessible for the five-gun build. The exception is the wife wanted spiffy triggers on one of the compacts and on her full-size. So, that 380 price includes Zev triggers. I could have had it down to about 330 without those triggers. Given what I know now, I can achieve 85 to 90% of what Zev does on a stock trigger kit.
So what was my issue? the gun would hang up, 1/8 of an inch before going into full battery. If you tilted the gun down and it would go into battery. It did not take much for it to go into battery, but when I started out 80% of the time, it did not. I worked on the locking block/barrel-locking lugs at least five times. I tested the guns between each bit of work. I worked slowly and stopped when I felt I had made some improvement. Why not go whole hog until the gun worked perfectly? Well, the gun will mate together as it is used. In my experience, smaller improvements work better in the long run.
So, not the cheapest parts, but still cheaper. Case in point, the locking block from p80, and the 80% guns Barrel and slide. The barrel has some kind of finish, but the finished area of the locking lugs was thicker and rougher. I applied some bore bright to the locking block and locking lugs. I worked the action for quite a while and looked at where the wear was.
You can see how much of the finish and the rougher stippling on this barrel at the lock-up area.
So that was the barrel; here is the locking block on gun 1. You can see the pebbled finish on the locking block. I smoothed much of that out with some fabric 4k paper. Why did I do this? This combo of barrel, and locking block rubbed together on the left and right. It was one of the areas the bore bright cleaned up first. After a couple of thousand actuations the sides of the barrel locking lugs and the locking block were smoothed up.
Here are gun two's locking lugs. I've applied Sharpie before the shooting session to see where the mating surfaces are. This is an improvement on where I started. Like gun one, gun two's tolerances are stacked to the point of interference.
The locking lugs of barrel two from gun two.
Now gun two did not have the same problem with the sides of the barrels locking lugs binding with the locking block. It's issue was simply tilting back into place. Here you can see how thick and pebbled the barrel's locking lugs were.
So, how are they working now?
Well, both fired two hundred rounds pretty well. The last 150 out of each were without issue. What does that tell me? The guns are smoothing out, and I expect the more I shoot them, the smoother they will become. I am ready to find red dots to put on them and source some more mags (I've been working on three types of compact mags, and two types of g17 mags.
I have stronger spring kits coming, and both will receive an upgraded spring. (I'll start with the 18lbs and work my way up).
A note on the triggers, slides, and all of those mating surfaces. They also needed checking. All 3 zev triggers did not engage the strikers (OEM, or zev) fully. I tried a factory glock pistol and ran into the same issue. I had to heat and bend the tabs on the striker catch on all three. The cheaper Brownells Gen 3 LPK worked out of the bag. The Zev is significantly smoother, but, the trigger bar did drag on the slide; the return tab was also rough and didn't ride smoothly in the slide's kick-out.
I'm not blaming Zev for that as I've got relatively cheap slides, but I did notice it, so even high-end parts can have tolerance issues. In the end, I took my oiled fabric 4k paper and cleaned up the points of contention on all five triggers (two OEM and three Zev). That was the single most significant improvement to the guns. Prior to that, all five would hang up right before the striker's safety plunger. After that, the three compacts had a few issues that normal shooting took care of. The two full sizes were the only ones where I needed to work on the locking block/lugs.
