Sunday, June 17, 2007

Past the pins.

And honestly, these are some of the best photos yet. Secret? Tripod. 28 photos.

Partial detail strip and explanation, CZ75

By the way, DO NOT ATTEMPT WITH DECOCKING MODELS. If I recall correctly, they're put together on a jig at the factory. You don't have the jig, and neither do I.

We start where we left off: one CZ75B Compact .40S&W, field stripped, grips off.

The first thing to do is remove the mainspring, which you do by removing this pin. This pin is held in only by spring tension: you'll notice the mainspring "plug" sticks out a little at the bottom. Press that against a hard surface and the retaining pin will almost fall out by itself. In fact, with use it may very well do so.

And there you have it.

Simply pull the mainspring free. Some brake springs won't allow this until they are also removed.

Now remove the magazine brake spring. This pin retains it, and may need to be pressed free. These pins are retained partially by the grips so a loose fit is alright.

The mag brake and it's pin.

Here is a closeup of the fire control parts. You may refer back to this for a closer view of the parts I'm referring to in the next few sections.

Pointed out is the longer leg of the sear spring. It's function is to retain the safety, along with:

The safety detent plunger. CZ saw fit to leave the top accessible with a fork so you can pull it back with a small pin or screwdriver.

With the spring leg lifted out of the notch and the plunger pulled back, the safety slides right out. The fire control insert is now free of the frame and is shown in the middle.

This is a closer view of the double action leg and trigger bar, and clearer views of the safety retention devices.

Pointed out, the retaining tab for the right hand safety.

The tab simply lifts out of it's groove. To remove and insert the right side safety you must also press down on the trigger bar.

The small coil spring is the tensioner for the safety detent plunger. The plunger will simply press out to the inside of the frame.

The safety detent plunger.

The spring for the safety detent holds down the retaining pin for the hammer pin. It's free floating, just turn the frame over and it falls out.

This frees the hammer pin. This pin is also loose fit, and can simply fall out.

Pictured, the hammer, hammer pin, and retaining pin. On the left of the hammer body is the double action arm, on the bottom is the mainspring strut.

Pointed out here are the surfaces on the trigger bar that make the pistol work. The inside, lower surface presses against the double action arm, and the outer surfaces interact with the fire control insert for single action mode and for the firing pin safety.

Now let's take a look at the fire control insert. At the top (forward) you can see the ejector. The tab towards the bottom is the firing pin safety lever, it lifts under trigger pressure and presses the firing pin plunger up to free the pin.

A view of the bottom, with flash fill. The two underhanging tabs are the key to operation: (left is forward)

This tab is on the sear. When the trigger bar presses it the sear surface lifts off the hammer.

This tab is on the firing pin safety lever.

This is the sear surface.

There is one pin in the fire control insert, it holds everything together. You'll want to use somethign as a slave pin in order to get everything apart under control.

From right, clockwise: Insert body, sear, firing pin safety lever, FPSL spring, insert pin, sear spring

There you have it. That's as far as I'm currently capable of going since the trigger pin is severely staked and would need a replacement that I don't have, were I to remove it.

The operating table.

Assembly is the reverse of disassembly.

There you have it. I won't get to the CZ52 this weekend, I want to do some studying first. But, it will be done... it was my second gun, naturally it's next in series.

Wednesday, June 13, 2007


I detail stripped the CZ75 .40, except for the trigger assembly.

I photographed the whole thing, in a way that I can easily explain every single part's function.

I permanently deleted the photos before I saved them.

*smacks forehead* I'll try again over the weekend, and do what I can with the CZ52 as well. I doubt I'll be detail stripping that one though... I don't want to risk damaging it.

Tuesday, June 12, 2007

To the pins...

Alright, I respond to a good egging-on. I got home from a long day of work, grabbed the CZ75B Compact .40S&W out of the closet, and stripped it almost to the bones.

Why the .40? It's cleaner, and it's the one that won't cause too much pain if I break it. It's never quite worked right thanks to a wonky original magazine that I haven't bothered to replace yet.

Anyhow, without instruction, I got it down to where two more pins would have had it completely apart... the trigger pin and the main pin for the sear assembly. The trigger pin is strongly staked in, and the sear pin really needs pliers and a real pin punch, of which neither was at hand.

Surprisingly, the gun comes apart almost at a touch. None of the other pins are friction fit, they're held in with other items like a puzzle. The safety lever is held in with the leg of the sear assembly spring. The cross pin that holds the hammer pivot pin in place is held in by the spring for the safety detent plunger. The right hand safety is held in with a little metal tab that's in turn held in place by the sear assembly. It's a little work of art :)

In turn, I also discovered that the magazine release is indeed reversible, a "freefall" mag brake spring really is just a flat piece of steel, and the same spring that holds the slide release in place is the one that tensions it downwards. Oh, and that all three have been engineered to simply not break. DA parts are huge.

It's an impressive design. And now that I'm reasonably comfortable with it, expect pictures next time (though, out of turn).

Saturday, June 09, 2007

Finally! Guided Gun Tour #1

CZ-75B Compact, 9x19. Date of production 1997.

This was my first gun ever, and the one I've shot the most of all of them. Now, before we proceed with photos just bear in mind the gun's still a little oily and is picking up dust and lint, and that does show in the photos since they're supermacro and so close.

Firstly, I tend to closely inspect everything before I clean it just to make sure that when I'm brushing, flossing, etc. that a part's not going to fall off that I won't notice. Well, I've noticed that the fire control insert wobbles a bit... the hole for the safety "pin" are hogged out a bit.

The following two photos are safety on/hammer back, first with trigger released and second with trigger tension. Notice the gap between the insert and the frame closes up, by a measured ~.0025 inch.


As you can see the CZ75 uses "Browning" style barrel lugs inside the slide ahead of the ejection port.

The barrel disengages using a modified cam action, using the slide stop pin as a lug. Note that the track is fully enclosed; this serves to completely control motion in both disengagement and engagement as well.

The CZ75 9mm chamber isn't fully supported but is very close. Note the protrusion above the chamber; I have not figured out the why but my best bet is that if you have a case head rupture that will serve to keep gases and debris from travelling upwards, i.e. into the shooter's face.

The extractor is simple, external with a pin pivot and a coil spring ahead at the front.

Here at the breech we notice two things; the extractor is set up for controlled feed (large control surface, ramped on reverse from the bottom) and you can see the notch for the protrusion we saw above the chamber. Rails are "internal", cut into the inside of the frame and the outside of the slide. Note the "divot" on the bottom of the rail on the left, this is for disconnection purposes. The trigger bar serves as the disconnector.

Here is the complete fire control insert (CZ's terminology is probably different). You can see the "hump" on the trigger bar that matches with the divot in the slide, again for disconnection purposes. Moving up you can see the ejector, the tumbler for the safety... ok, this is probably a bit hard to describe that way. Let's try this; see th ecoil spring dead smack in the middle? The piece immediately above that rolls towards you when you pull the trigger. Underneath is the sear interface; the leg on the right rolls downward and is stopped by the safety tumbler when it's engaged. The leg on the upper left moves up under trigger press and disengages the firing pin safety. Just ahead of the hammer you can see the half cock notches.

CZ provides a witness (witless) mark that makes assembly and disassembly easy.

Under the grips, we have the brake spring and the main spring and strut. Very simple stuff. CZ sells a flat brake spring so mags drop free, otherwise that leaf of metal "brakes" the mag and you have to pull it free. Grip profile is reasonably simple and I may try making my own sometime.

And there you have it; the prototype guided tour that I want to do for every gun I own.

This CZ compact is a steel framed model and is heavy, but small, about the size of a Sig P239.

CZs are rather slim in slide profile thanks to the rails being inside the frame. It does carry like a smaller gun.

And here's the prerequisite "what I carry" shot. Yes, that's a classic Motorola alpha pager, someone thinks I'm important.

In the future, I'll figure out what to do about having a light box; these were the best I could do using an overhead 100W. I should probably also wait a few days after cleaning to get the "loose oil" spread around and not so sticky to lint and fluff. A tripod would be handy as well.

Next up: The CZ-52. When? Beats me, whenever I get to it. I want to make at least one of those improvements to my method first, and I also think I want to think into these a bit so they aren't so random.