75B SA vs 75B .40

[ruber]

I have a love/hate relationship with CZ's. I've always liked Brno rifles and got into CZ rimfires from that. I got my first 75 series handgun in 2004, well after the addition of the firing pin block and the changes in manufacturing (automation, CNC, etc.). I wish I had a pre-b 75 or at least a Czechoslovakia marked gun. Alas that is not in the cards for me, so here we are....

I have had multiple 75B's, a SP01, and a couple 2075 RAMI's.  Only one I ever really enjoyed was a 2013 75B in 40 SW that had full rails on the slide and ambi safeties. It shoots very well but is a heavy, chunky, block. So I kinda forgot about CZ's for a while until this SAO model popped up in a local shop.  It was a project gun at a project price. It had grips that didn't fit and were not screwed down, there was rust on the hammer and under the safety levers. But I like the frame and decided to pick it up.

Here it is with the 75B in 40 after I cleaned it up, replaced the trigger with a CGW SA trigger adjustable for both pretravel and overtravel, polished the trigger bars & frame, hit the rust on the hammer and safeties, and replaced the grips with some Guuun grips.



Some differences between the two- the tang on the SA is a bit upswept (this is my favorite frame, it is not a shorter reach nor does it allow for a higher grip, but it is much more comfortable and quite a bit lighter than the SP01 frame). The safeties are larger and allow you to ride them with your thumb. The SA also has an extended magazine release which can be reversed (this is what caused the grips to not fit when I bought it). Internally, there is no disco on the SA models allowing you to adjust the trigger pretravel much more easily. The hammer is also lacking the half-cock notch so it is easier to tune the overtravel.

The 75B SA is unique in the 75 series. It has a slide that retains the full width for the full length, but tapers  slightly right at the muzzle and does not have full length rails. Other 75's with a full width slide like the 40 in the picture, the SP01, and the shadows have a larger barrel outer diameter, but the SA retains the smaller barrel OD of the standard 9mm 75's. This makes the total weight a little more than the standard 9mm 75B, but about 0.3 ounces lighter than the 40 sw version, which I like.

So... I took it to the range. The gun felt great, lined up great, the trigger pull was great, the bullet hit right where I wanted, and the brass hit me in the forehead.  And that takes me to the hate part of the relationship...

[ruber]

So...  I took it apart again as there are a series of break in issues that plagued many 75B series pistols from about 2005 through 2018. I'm not sure why it took so long for CZ to address, maybe they make individual parts in large batches.  But these items are listed in the Original CZ Forum as common break in issues.

The erratic ejection is often caused by the ejector on the sear cage not being finished/shaped properly. This is an easy fix but requires removing the cage to do a nice job on it.  The top photo shows the ejector as it comes from the factory (same as my 2013 75B in 40, my 2017 SP01, and my 2004 RAMI). The second photo shows the modified ejector with an angle that helps with not directing brass into the shooter's forehead.





I also swapped out the recoil spring for a 13lb spring and beveled the lead in edge of the slide so it does not drag on the round in the magazine. This makes for a smoother feel and more reliable chambering.

I was curious about this gun as it had substantial external wear, but the barrel and slide looked almost new.  I'm thinking the previous owner did not like getting pelted with brass either.

The gun was lighter than my 40 sw variant, but I wanted lighter still.  I put on a set of factory take off plastic grips which are about  0.5 oz lighter per panel than either the Guuun  grips or the original rubber grips. They are not as thin as the Guuun grips, but to remove a full ounce, I'll take it. This got the 75b SA to weigh in at 33.0 ounces.  Close to my MkIII HP, so pretty happy with it.



Back to the range tomorrow....

Edited to add:
Got the sear cage from an older 75B from 1996. The face of the ejector is certainly more angled with the lower inside corner beveled off than recent production. It is at a different angle and more subtle than my modified version, but still gets the contact point further out on the rim.

[ruber]

I went to the range after work today and ran 100 flawless rounds through it. It is amazing how your groups can tighten up when you get rid of that flinch...

The other thing I did that I forgot to mention was I blacked out the rear sight (yes, they can be turned around too, but a sharpie made quick work of it) and I brightened up the front sight with some fresh white sight paint in the dot. That combination works well for me.

I'm not quite sure what the intended market was for the SA variant. It is not a race gun, nor a bullseye gun. With the slightly heavier slide and slightly lighter frame with the upswept tang, it is an exceptionally smooth and accurate shooter if you take your time. A very nice range gun that can do double duty for personal defense for those happy to carry condition 1.

[Bob Reed]

Very nice pistols, gunsmithing & review w/photos, Ruber.

Like you and many others, I'm also a single-action automatic kinda guy, and while I like the 75 B SA, I really wish they would offer a regular 75 B in SAO.

[ruber]

Me too. I'm also keeping an eye out for a standard 75B slide and putting that on this frame. A little bit more slender and a little bit lighter...

[Bob Reed]

Hello, Ruber,

When you recut the ejector, do you leave the face square, or do you angle it back a bit on the R.H. side - and approximately, what does the face 'contact area' above the rearward angle measure in height?

Also, you said, quote: "I also swapped out the recoil spring for a 13lb spring and beveled the lead in edge of the slide so it does not drag on the round in the magazine. This makes for a smoother feel and more reliable chambering."

What do you mean by "lead in edge of the slide"? BTW: I'm not trying to nitpick, and I think I know what you mean but I want to be sure...

Thanks Ruber, and Thanks Again for the good thread. I really enjoy working on the 75s too.

[ruber]

Hi Bob,

Sorry I did not get those up.  I went back to the range with it last night and ran through a couple Rangemaster drills. I had a couple pieces of brass land softly on my elbow, so I will likely go down to a 12 or 11 lb recoil spring and when I swap them I'll take some better photos.

To answer some questions for now, I did leave the face square for now on this one. On a previous SP01 I did angle the face of the ejector a bit so it made a small squarish point at the top left corner (as though you are aiming the gun away from you), but I often feel less is more, so I was not as aggressive with this one. The main goal was to relieve it a bit so the bottom of the ejector is not making any contact at all with the brass.  I'm going to swap the recoil spring and see how it does before I do any more shaping on it.

As for the lead in edge, this is something I do on every CZ.  The edge (circled in red below) comes with a very sharp cut on it, the edge that rides on top of the next round in the magazine being rough to the touch.  I knock it down with a stone a bit, not so much that it does not easily pick up the top round, but enough that it is smooth when dragging across the next round in the magazine. I've found that if you can get that to be very smooth, you can reduce the weight of the recoil spring without the need to increase the weight of the mag spring.

I also polish the surface with the yellow line on it shown below.  This usually comes a little less smooth from the factory, and taking care of this and the lead in edge can make these guns a lot smoother right off the bat.  This all happens with break in, but I seem to get either new guns or used guns that have been shot very little.

I'll get some better photos and measurements up soon.

Thanks!
Chris


Ps. The SA frame is a great platform for the Kadet...

[Bob Reed]

Thanks Chris, that's the area I thought you were talking about, and I've lightly hit the same spot on a few pistols as well.

One part I modify is the slide stop; I gently break the outboard edge in the slide stop's spring groove, so it requires less force to remove the slide stop - and I recontour the tip of the slide stop's shaft in order to make reinstallation much easier. The slide stop's shaft/pin is slightly shortened as a byproduct of the recontouring, and I'm thinking about shortening them another .030" or so due to them being excessively long to begin with.

Thanks again, and please let us know the height measurement on ejector's contact area when you have the chance.

PS: What ammunition are you using to require the lesser weight recoil spring?

[ruber]

So... springs....

I like to be on the reliable end of things, including when using rimfire ammo in the Kadet kits. So I keep the mainspring up around 20-22 lbs which is a lot heavier than the 11-13lb hammer springs in the CGW comp & carry kits. But, I have never had a failure to fire and don't really care to lighten the DA pull of a safety model 75. On top of that, the heavier slides of the CZ's that I own (the 75BSA, SP01, and the 75B in 40 with a 9mm conversion barrel) slow the recoil allowing the "recoil" spring to really be more of a "return to battery" spring.

Most of the time I tend to shoot the cheapest range ammo which is usually 115 grain from S&B, Fiocchi, or LAX. With the factory 16lb recoil spring and 20 lb mainspring, I have had failures to pick up the next round.  And I like the brass to get flung out in front of me a few feet off to the right. 

So I have gravitated toward the setup of having a heavier mainspring and lighter recoil spring. It gives a nice smooth flat shooting feel to the gun, the brass clears the area nicely, and it seems to be much more reliable than many other setups I've tried out.

Hope that explains my somewhat non-traditional preferences.

-Chris

[ruber]

Sept 15, 2023 11:40:09 GMT -5 Bob Reed said:

Thanks Chris, that's the area I thought you were talking about, and I've lightly hit the same spot on a few pistols as well.

One part I modify is the slide stop; I gently break the outboard edge in the slide stop's spring groove, so it requires less force to remove the slide stop - and I recontour the tip of the slide stop's shaft in order to make reinstallation much easier. The slide stop's shaft/pin is slightly shortened as a byproduct of the recontouring, and I'm thinking about shortening them another .030" or so due to them being excessively long to begin with.

Thanks again, and please let us know the height measurement on ejector's contact area when you have the chance.

PS: What ammunition are you using to require the lesser weight recoil spring?

Thank you for the tip on the slide stop, that all sounds good and I think that will be my next step.

The height on the ejector's contact area currently measures 0.040". Like I said, this is less aggressive than I've done in the past, but now II am just taking off the minimal amount to keep my forehead from bleeding.

Also, I didn't come up with this in on my own, I have been a member of the Original CZ Forum on and off for several years and saw much of this info over there. Here is a link to the sticky on common break in problems that helped me figure a bunch of this out:
czfirearms.us/index.php?topic=22862.0

I also got a bunch of info from fellow San Diegan kneelingatlas over at Brian Enos's forum where he has a great thread on tuning, polishing, springs etc:
forums.brianenos.com/topic/191773-cz-tuning-101-with-professor-atlas/

(please let me know if I can't post other forum links here and I'll modify this to just include descriptions of the other threads)

-Chris

ps. In the kneelingatlas post, the ejector is not angled nearly as much as either mine or the one on the CZ forum but is still angled slightly in the same direction as opposed to mine which actually had a slight angle in the opposite direction such that the bottom of the contact patch was more forward than the top.  Machining tolerances??

[Bob Reed]

Chris, - Thanks for the measurements, etc. - and the links too, it's OK to post them.

BTW: If you feel like it, please start a thread and share some tips on shortening the reset on the regular 75 B Series. The other nite, I outran the trigger on my 75 B twice and I'm thinking about 'things', but I also outran the trigger on my 1911 as well doing the same drill and it's reset can't get any shorter. Needless to say, the rate of fire was high...

[ruber]

Added photos of the old style sear cage from a 1996 75B to my second post above.

Sorry about the grime...