So you want to build a CZ Open gun?

[kneelingatlas]

Every so often I get a message about CZ Open guns and since they've been comming more frequently in the past month I decided to start this thread, hopefully it will become a great resource for anyone interested in coming to the Dark Side, CZ style

Disclaimer: Open is not for everyone, it's loud, fast and EXPENSIVE! I want to emphasize this because I hate to see people get in over thier heads financially and there are pleny of other divisions in which you can be compeditive and have lots of fun with less initial investment and less expensive components. It seems like a lot of people want to build a custom Open CZ as a cheaper alternative to the Czechmate (CZs factory Open offering), but unless you are very handy and are excited about the adventure, you will almost certainly be better off with the Czechmate.

With that out of the way, let's talk about Open CZs! When I first got into USPSA I shot a range rental Tactical Sport in 40 and fell in love First and foremost I loved the trigger; when I was young I shot 25M Rapid Fire Pistol with a Walther OSP 2000 which had a trigger pull weight of 47g (that's 0.1 lbs for you English folk!) so I'm a real trigger snob as you may have gathered from my DA tuning thread: CZ Tuning 101 with Professor Atlas. I had seen other shooter shooting Open and knew that's where I really wanted to be, but I wasn't yet reloading, the Czechmate had a prece tag nearly three times as much, and lastly I was scared of being a noob stepping up to the line with a $3,000 race gun on my hip and making a fool of myself.

So I bought a Tactical Sport and promply began turning it into an Open gun

It wasn't long before I gained access to a reloading press and started experimenting different loads and comps:

I ended up with a modified three port Tanfoglio comp and a chopped dust cover:



As you can see I got it shooting pretty flat:

but it was very heavy, 52oz without a mag! By comparison the Czechmate is 49.3oz with the same optic which is pretty heafty as well, so I embarked on a new project: a 75 SA based Open gun

This "Baby Czechmate" weighs 42.5oz and swings around much easier. As you can see I modified the last port of the Czechmate comp, but the biggest gains were made by opening up the first port:

This is all I have time to write now, but I'll get to the more on the process of building a CZ Open gun later

Edited August 3, 2015 by kneelingatlas

[eerw]

John..you are a wealth of knowledge and experience on this topic. Appreciate you taking the time to share your information.

[Toolguy]

Thanks John. I'm following this with interest as I may build a Bianchi open gun on a 9mm TS.

[kneelingatlas]

The hardest part about a CZ Open build is the comp, unfortunately for aspiring CZ Open shooters all the comp design development is being done for 2011s. 2011s use either "bull barrel" comps threaded 0.685"x40 or cone comps designed for use with busing barrels threaded 0.575"x40. Here's the scoop on CZ barrel sizes:

The 75B, 75B SA, and the P01 (there may be others I'm unaware of) utilize a barrel with an OD of 12.75mm (0.502") for 9mm, but a barrel with an OD of 14mm (0.551") for .40.

The SP01, Shadow, Champion, Tactical Sports and Czechmate all use the same OD barrel for 9mm and .40 (14mm); the factory thread for the Czechmate and Champion is M14x1.

On the Tanfoglio side, the small frame pistols use 14mm barrels and the large frame pistols use 15mm barrels. The factory thread for small frame is M14x0.75 and the M15x0.75 for large frame.

There are some factory comps floating around for small frame Witnesses (http://www.gunpartscorp.com/Manufacturers/EuropeanAmericanArmory-33215/AutoPistols-36073/WitnessFullSize-34951.htm?page=4) and CZ USA seems to be stocking Czechmate comps regularly now. I have my own taps/dies and thread my own barrels, but it seems to me there are very few gunsmiths who cut metric threads.

I ended up with a few comps from the Springfield custom shop which were threaded 0.540"x40 and since that was a proprietary thread I welded up the hole, re drilled it and tapped it with a M14x0.75 thread to match my barrels; that's an option, but not a very easy one I've also made thread adapters from M14x0.75 to 0.685x40 which work really well.

[kneelingatlas]

So if you want to screw a comp onto the end of your barrel you need a barrel long enough to stick out the front of the slide. The first thing you need to know is that in the US the barrel lengths advertised don't match reality; don't take my word for it, check with a ruler for yourself. The full sized guns like the 75B and the SP01 have 4.5" barrels and the TS/CM have 5.1" barrels, the nice thing about this is that you can put a TS barrel in an SP01/Shadow slide and it will stick out 0.6" which is plenty to thread and attach a comp. For the slides which use the skinnier barrel, CZ makes and sells a 6" barrel, the downside of a 6" barrel in a 4.5" slide is that you most likely need to cut the barrel to length which adds an additional step and specialized skills. The nice thing about the skinny barrel is that you can thread it 1/2"x28 and use any number of off the shelf comps (although the slide profile won't match like the Witness comps do). This is by far the cheapest/easiest way to compensate your CZ. Here's a picture of one dcloudy777 did using a Lone Wolf Glock comp:

[kneelingatlas]

This picture reminds me of something which needs to be considered is the fact that when the slide cycles the barrel moves back relative to the frame, so your comp will hit the frame without clearance, which is one of the two reasons I like the short dust cover frames for Open over the SP01, the other being the added weight. Static weight may help fight muzzle flip, but in Open you're using the comp to fight muzzle flip, so the rail just makes it heavier; that being said there are plenty of good Open shooters shooting 50+ ounce guns plenty fast, but I prefer a lighter gun.

[kneelingatlas]

This 75 SA based gun was my lightest with a plastic dovetail mounted optic and an aluminum comp:

With all the comps I've tried and the big C-More lenses I'm used to using I'm a little spoiled so this one didn't make the cut.

Edited August 4, 2015 by kneelingatlas

[adamge]

Any tips on tuning a Czechmate factory comp for 9 major in an otherwise-stock Czechmate?

[kneelingatlas]

Yes, increasing the size of the first port increased the effectiveness of both my Czechmate comp and my three port Witness comps; I used the Dawson Awesome comp for a guide and cut the first port to 0.465". To do this on a stock CM you would need to cut back the barrel a little. I haven't tried it yet, but I also think the CM could benefit from two 1/8" to 3/16" holes in the barrel at 12 o'clock.

[jdd817]

Awesome thread, as I'm currently looking into building a small-framed open gun as a backup to my Czechmate. Should I decide to go with a Czechmate comp (also considering some of the Witness comps), what is involved in fitting the comp? What about the concealed hammer? My understanding is the TS frame hammer is a bit wider than the 75 frame hammer, what would be involved in getting the concealed hammer to work?

Last question I have is the big sticks. Is there anyone out there with a history of welding those up for the small framed mags? What kind of capacity can you expect from the small frame mags (currently I can get 28 reliably in my CM big sticks, likely could get it up to 29 with a bit of work).

Thanks!

[cpa5oh]

This thread is going to be great.

Questions I had about an open CZ are:

- will the CZ barrels reliably handle 9mm major over thousands and thousands of rounds?

- starting with a TS would be ideal I think - but there's the issue of the serial number being out near the end of the dustcover...no one I've talked to has known if/how a serial number could be moved.

- details on how the barrel/comp gets fitted up to the slide (muzzle end)

[kneelingatlas]

jdd817, the 75 SA slide needs to have the bushing removed plus opened up a bit more to fit the CM cone. The SA slide is a little shorter than the CM slide so the barrel needs a few more threads and a slight trim.

The TS hammer fits the SA frame without modification, it's the notch in the slide which is narrower, you can narrow the hammer or open up the notch on the slide.

Bill at highercapacity.us will weld two tubes together into a big stick; I've also cut Pro Mag 30 rounders to length, they make a 20 round that might come to 170 with the right base pad, I've never played with them.

My CZ75 big sticks hold 28+1.

[kneelingatlas]

cpa5oh, I've fired ~4K 115s over 1,470 fps throut the oldest of my barrels without any noticeable loss of accuracy.

An FFL 07 can file a form with the ATF and relocate the serial number.

The CM barrel is the same length as the TS so to convert a TS, you need to cut back the slide. I've never cone it, but I think the cone is sized to fit the slide without the bushing.

[NoKimberDave]

Awesome thread!

kneelingatlas: you should consider moving to North Carolina, preferably next door to me.

Edited August 7, 2015 by NoKimberDave

[cpa5oh]

Any idea where to get details on this? A local FFL 07 wasn't aware of this, I went to the ATF's website and went through all of the available forms and couldn't find anything...

An FFL 07 can file a form with the ATF and relocate the serial number.

[Gooldylocks]

Any idea where to get details on this? A local FFL 07 wasn't aware of this, I went to the ATF's website and went through all of the available forms and couldn't find anything...

An FFL 07 can file a form with the ATF and relocate the serial number.

My understanding is its kind of an "off menu" item, so I'm not surprised you can't find any information about it on their website. Lots of talk about doing this for certain makes of AK sporter or SL8 to G36 conversions.

[kneelingatlas]

Ask and ye shall receive:

ATF Form 3311.4 - Application for Alternate Means of Identification of Firearm(s) (Marking Variance)

Any idea where to get details on this? A local FFL 07 wasn't aware of this, I went to the ATF's website and went through all of the available forms and couldn't find anything...

An FFL 07 can file a form with the ATF and relocate the serial number.

Edited August 11, 2015 by kneelingatlas

[ranger]

I shot a Springfield Armory P9 (CZ clone) way back when in the days I shot Open. 9 Major was not "legal" in ancient times so they were converted to 9x21. I believe Major PF was higher then too? That was before the S_I pistols became widely available. Should be lots of information about the old days of CZ clones in Open.

[kneelingatlas]

I never got around to fixing re hosting the pictures in this thread, but here's a picture of my first CZ Open project in the beginning:

 

and now:

[adamge]

Is the comp long enough?

[kneelingatlas]

2 minutes ago, adamge said:

Is the comp long enough?

 

You're laughing, but I did have plans to use the full length of the 6" barrel, with those ports on the end of it, making it 0.4" longer.

[kneelingatlas]

I'm thinking about shooting this one in a match this weekend:

 

 

For comparison my first TS Open gun weighed 54oz, the one above weighs 44oz and a similarly equipped Czechmate weighs 49oz.

Edited February 8, 2018 by kneelingatlas

[3gEric]

Awesome setup...... Is that a cz 75sa slide with a 6" barrel? I see that the slide was untouched and wondered if that comp was not a coned comp. Also, is the cmore cheely's cz specific mount or a 2011 type mount? Any info will be appreciated, thanks

[aandabooks]

On February 7, 2018 at 10:30 AM, kneelingatlas said:

I never got around to fixing re hosting the pictures in this thread, but here's a picture of my first CZ Open project in the beginning:

 

and now:

 

What did you have to do to move the serial #?  

[kneelingatlas]

13 minutes ago, 3gEric said:

Awesome setup...... Is that a cz 75sa slide with a 6" barrel? I see that the slide was untouched and wondered if that comp was not a coned comp. Also, is the cmore cheely's cz specific mount or a 2011 type mount? Any info will be appreciated, thanks

 

It's a 75 Omega slide, 6" barrel with a bull-style SJC Glock comp.  Cheely Czechmate mount.