CZ Open Build Theory

[kneelingatlas]

I never got set screws to work without drilling a cup for them to sit in and using red loctite on them.  Sort of defeats the purpose.

 

The Czechmate style comp is loose and just keeps from rotating with a long guide rod.

[Rusl]

On 8/22/2018 at 6:37 PM, kneelingatlas said:

 

Hi, 

 

I have never built a compensator but due to the importation limitations I have I'm interested in having a go, I understand the general principles of how they work but unfimilair with them on semi auto pistols. I was hoping you guys might be able to answer a few questions for me or point me to a book or thread that would help me design and build, I have access to a full machine shop so actual construction should be alright, it's the design and material I'm slightly unsure about.

 

This bottom picture, is that comp available or a one off, is it a cone style or for an extended barrel? This is the look I am after.

 

With a cone style compensator my understanding is you just thread the standard barrel then remove the barrel bushing from the slide. When machining the compensator it has a cone on the rear over the threads so when the slide runs foward it lines up and locks the barrel, have I got this correct?

 

Is the cone best to be tapered the whole way up to the brake or have a taper then small flat area similar to a barrel bushing setup?

 

Is it worth installing a bushing into the slide that is a reverse of the cone? This would offer the barrel some support during the reload cycle of the gun?

 

What would the best material for the cone be? I'm assuming if I was to machine a aluminium comp I would need to make the cone from steel. Would standard mild steel do or am I needing to look at stainless steel, chromemoly or even tool steel? 

 

What steel is a standard barrel bushing machined from?

 

Thanks for the input if any one has some, love the build pics and once I get mine done I will post up pics.

[kneelingatlas]

6 hours ago, Rusl said:

 

 

The bottom picture is of an SP01 slide (factory bushing intact), threaded Tactical Sports barrel and factory Tanfoglio small frame comp.  This is the easiest way to go.

 

You have a good understanding of the cone comp, typically the cone tapers all the way to lockup by I've seen them with a small flat, it's all about the final fit.

 

I've never seen an inverse cone inside the slide and I can imagine complications with barrel removal, so I wouldn't recommend going down that road.

 

My aluminum comps have aluminum cones as well, they're all one piece.  The harder the material of the cone, the more you're going to wear the slide and comps are more easily replaced than slides, plus the mating surfaces wear in nicely with a softer comp.

 

It's important not to imagine you're going to make one Open gun to last a lifetime, building your own Open guns is a continuous project with constant opportunities for improvement coming to light as you go.

 

You're going to make many comps as you learn how these parts interact with use.

[arkadi]

Aluminum is surprisingly good material for a comp.

Round everything to prevent cracks.

 

Cracked titanium and steel comps:

 

 

Works for me:

 

[Rusl]

So much good information here thanks, I just re read the entire thread again, must be the fourth time and still picking up bits.

 

If i go with a comp aluminium it is for the comp and cone then, I prefer that as I want to keep weight down and it's easier to machine.

 

So is a tactical barrel and a cm barrel the same? And will they both fit into a SP01 if I can source one?

 

For thos that have played around with barrel porting, this is a steel challenge only gun, so light loads, minimum to make the gun function reliably. Would just straight porting flatten the recoil out as much as a small comp? I'm not worried about recoil just trying to keep the gun flat so the dot tracks quicker, and I'm trying to keep the gun light.

 

Does slide lightening have a dramatic affect on muzzle rise and drop in the reloading cycle, is this a better or worth while thing to be looking at?

 

Just generally if you were building your own open steel challenge guns, open to any modifications but shooting min pf or less what would you build?  Would you port or comp, lighten slide?

thanks again.

[kneelingatlas]

A Tactical Sports barrel is the same length as a Czechmate barrel, they both fit in an SP01 slide, but the Czechmate barrel has a longer threaded part than what sticks out of the slide.

 

I've done it lot of expermenting with holes and I could take them or leave them.  As far as making a gun shoot flat with light loads, the best I've done is a 95gr bullet over a large charge of AA7 or Shooters' World Major Pistol.

 

CZ slides are inherently lighter than 2011 slides and I don't recommend going lighter than ten ounces, so I think of slide lightening as primarily cosmetic.

 

I'm not a big fan of ports without a comp, I suggest a good comp with or without ports.

[Ludde]

Now I have got it to run reliably with major 165-167pf 124gr bullets. Initally I had problems with the empty cases getting stuck in the chamber and the extractor slipping off the rim. Since then I've polished the chamber and added a Wolff extra power extractor spring.

 

The gun feels soft and does not slam into the hands, I am going to test a little more powder to see if I could decrease some of the muzzle flip. If that does not help it's probably due to the design of the comp having many sideports and small up ports.

 

Some slowmo...

 

 

 

 

Edited March 14, 2020 by Ludde

[Ludde]

[Mauserlover]

On 3/10/2020 at 7:48 PM, arkadi said:

You could have a guide rod channel and barrel lug machined (for clearance), and a reverse plug installed, as per discussion somewhere above. Just never got to that point.

 

If I really-really need the barrel removed - due to a cracked comp for example - I use propane torch to kill Loctite and unscrew the comp. I also have a set screw in the cone.

 

Speculation: Glock guys who just tighten down a set screw never really shoot that much and/or they shoot plinking ammo. Until barrel thread and comp threads are matched exceptionally well, each shot will damage the threads.

 

Okay, also on the topic of, "why not just thread an extended barrel and screw a comp on", here's what I'm referencing...

https://www.lonewolfdist.com/Detail.aspx?PROD=919522

This page has a video, that's all I know about this. That and Physics classes all too long ago... 

They want you to screw their comp onto your barrel and just screw in a set screw. I'm foreseeing problems with the set screw backing out (surprise, surprise). Like you, I'm guessing they don't shoot it all that much. 

 

If you were okay with locktite and machining a channel at the bottom of your barrel for that set screw, what would be the problem? 

What if I machined a shoulder for the comp to stop against? Clocked with shims or machining the comp length down. Would that be better than just stopping with extra thread? 

 

From your post, what threads are being damaged? From the set screw, or from stretching due to the compensator wanting to go downrange and held on by the barrel threads? I'm thinking that the threads being damaged by the set screw would be fixed by machining a channel in the barrel for it; and the threads being damaged by the pressure generated by firing would be alleviated by screwing the comp down to a shoulder. 

 

Thoughts? Total neophyte here, I understand comps on rifles (where the bolt doesn't usually lock up on the muzzle end of the barrel!), but never thought until a couple of months ago that a comp on a pistol was even something I would ever pursue. 

I've got a CZ-85 that's undergone and undergoing a bit of a transformation, and at this stage, I'm reluctant to take the bushing out. Probably will happen as I get more experience working on short-recoil Browning based pistols. If anyone has a link or a suggestion of a book I should buy explaining why I should not be scared of cone comps I would much appreciate it. I'm just not seeing the benefit of removing the bushing and fitting a coned comp above keeping the factory bushing and screwing on a comp? I'm probably missing something big, and just don't know it. Any help is appreciated!

 

Just sent a check for my first open gun (thanks to the classifieds section here!) and when I get it in my grubby little paws (strike that, I've been washing them probably fifty times a day recently) I'll probably understand the cone-fit comps much better. Maybe. 

[Rusl]

This design using a set screew is so you do not  need a smith to set it up 9 lock the compensator in), ideally the comp should thread up against some sort of shoulder, this way the threads are loaded which will remove any play in the threads and stop it rotating. A set screw stops the  comp from rotating hopefully, but would not remove play from the threads, if your barrel and comp were perfectly matched you should get away with this but it isn't ideal.

If you really want to pursue this route I would machine a small brass disk  to drop in before the set screw, that would stop the threads getting damaged and give a more spread load as set screws can have quite a small tip that could wear and loosen under firing. Or as you say mill a small flat section for the set screw on the threads. 

[usmc1974]

On 8/22/2018 at 1:34 AM, kneelingatlas said:

Holy s*** 

Edited March 15, 2020 by usmc1974

[arkadi]

Sure there is a lot to tinker and learn about in Open guns, as demonstrated by @kneelingatlas.

Yet there is one simple scheme that is proven to work: high-temp red Loctite (I use 272) and a set screw.

 

If you will be able to machine a scheme where comp is correctly clocked when stopped on the end of the threads / shoulder - please share your experience. Keep in mind this should happen with a good relation to the slide.

 

@Mauserlover CZ85/75 barrel is too thin and its slide is too small for a cone comp.That's why we use SP01 / TS slide. The main reason to use cone comp is to reuse original barrel.

Edited March 17, 2020 by arkadi

[AcePrater]

Whoa, its been a crazy week. I'm just catching up on this thread. Lots of good info.

Ludde, that setup looks very nice. I hope it shoots well for you. Did you have to ream chamber to get maj PF?

Threaded barrel got lost in mail a few weeks ago - last one CZ had - now backordered, then original package shows up 2 weeks later...

 

I just swapped internals from old 75B SAO conv to the 01. I had been putting it off, and parts of it were bad, but not near as bad as I'd been building it up in my mind. I learned a LOT the past week. Fitted S2 ext. safety, fitted my first threaded barrel, troubleshooting reset issues etc..finding tiny springs in carpet...I thought I had a safety issue with my adj. sear, but turned out it was a broken detent spring.

 

So... I'm looking at comps now- any suggestions throw them up. Got some questions too.

• Like RonnieJr.s setup - that comp is a 40, would it still be GTG with 9-I can't tell in his pics if he is shooting 40.
• Comp suggestions Goodish/cheapish please - I'm good up to about $150 ish since I saved $$$ scavenging parts. I don't really care about looks, more function.
• Will/would PCC comps work OKish with this build- looks like most of these have large side ports which wouldn't be good.
• Can I just thread it on, time it with shims and try it out. I'm not opposed to the set screw and red locktite, but I want to make sure that all the other bits are GTG before it is locked.

Edited March 18, 2020 by AcePrater
removed dumb noob questions

[kneelingatlas]

@AcePrater

 

Using the full dust cover SP01 frame complicates things.  When the slide cycles, the barrel moves back relative to the frame approximately a quarter inch, so you need to think about the comp interfering with the frame.

 

If you're committed to the 1/2" threaded barrel the best off-the-shelf comp I've tried is the SJC 11 port: https://stores.sjcguns.com/sjc-major-9mm-11-port-aluminum-compensator/

 

You'll still need to create clearance for the frame unless you use the short dust cover frame.

[kneelingatlas]

Here's the simplest way to make an SP01 Open gun:

This comp: https://www.gunpartscorp.com/products/1447140

You may need to file the rails off the comp to get it to cycle smoothly with the full dust cover.

SP01 barrel: https://shop.cz-usa.com/ProductDetail/047004940706_Barrel-Tactical-Sport-9mm

Threaded M14X0.75

And a longslide Witness guide rod to keep the comp from spinning.  You'll need to drill out the hole in the slide for the guide rod.

[AcePrater]

Ahh.. more wool removed. thx. I meant to post my gun in the open poors thread as it seemed more appropriate, but it was late and stuff. I appreciate the info and will try to keep this thread clean of my noob ???s.

I think I'm going with the SJC Comp. After fitting my first barrel, I'm basically married to it for a while. I saw the relief cut on the frame of an 01 with same setup, and fell better about doing that than buying a new barrel and then treading and fitting it. Thank you for the link!

[Ludde]

So far I've not had to ream the chamber.

Loading .355 bullets 124gr to 29,55-29,65mm oal. Tested an 30mm oal would still fit before hitting the rifling. Let's see how it behaves with some more powder.

[Mauserlover]

Aha. So, I'm stuck with what is in my mind, the "easy" way for my CZ-85. I will have to get an extended barrel and thread it and time the comp. What I'm thinking is that I will square up the crown of the barrel, and have a shoulder in my comp so it will only go on so far, then work out my ports. 

 

However, if someone has a good resource (book I can buy, youtube channel, other threads, I'm good with whatever) completely explaining cone comps, and cone barrel lockup, I would much appreciate it. I got a Turkish knock-off CZ (Sarsilmaz CM9 Gen2) with the intention of seeing just how cheap I could make a decent open gun. Not knowing about cone barrel lockup at the time, and certainly not knowing about cone comps, I figured I'd TIG (okay, GTAW for those of you who like the new terms here) weld an extension on the barrel to thread for the comp. If I don't need to do that, that would be great! However, do I just use a tapered reamer in the slide? Do I make some sort of setup in the lathe to hold it? Or do I need the hole to be oblong to facilitate the tilting barrel, or is that what the taper is for? What angle of taper is best, or is it a pretty forgiving concept? 

 

This is why I need to buy the book. I just don't know what book to get. 

 

Thanks! 

[arkadi]

No need to overthink this. As @kneelingatlas pointed out it's all about final fit.

My comp/adapter currently have ~1.5mm flats, yet it was working just fine in early prototypes with taper till the end.

Make sure the result locks and unlocks smoothly without any perceived resistance and you're good to go.

Very important is to not let comp to screw on past it's final position and/or start hitting on the slide - directly or via the (steel) cone taper. It will go wrong very fast.

Edited March 20, 2020 by arkadi

[Ludde]

More testing with little improvement.

Bumped up the load to 169PF 8.2gr 3N38. Increased hammer spring tension.

 

 

[Mauserlover]

So... is the hole in the slide tapered to match up with the taper on the barrel, or is it just a square hole? (Square hole? Round hole, with square sides? Cylindrical! Cylindrical hole! Is it a CYLINDRICAL hole?)

 

What exactly is the benefit of a conical lockup if you aren't trying to salvage the barrel for a comp? Tanfoglio Witness Limited has a coned barrel, but no comp. Why? 

 

I think I'd still like to have a book so I can successfully overthink this. Is there one? 

Edited March 20, 2020 by Mauserlover

[kneelingatlas]

1 hour ago, Mauserlover said:

Tanfoglio Witness Limited has a coned barrel, but no comp. Why? 

 

1. Marketing

2. Weight

 

The marketing spin is that the cone makes a super tight fit for greater accuracy, my experience in reality is that slide/barrel fit varies from gun to gun and the cone barrels aren't inherently tighter than the straight barrels.

 

The cone does add a noticeable amount of static weight to the muzzle, creating a "bull barrel" effect.

 

ETA: the inside of the slide has straight walls which only touch the widest part of the cone.

Edited March 20, 2020 by kneelingatlas

[coolbox]

 What comp for 9mm factory loads (S&B 115gr), for steel plinking, on a SP01 based long slide and the new TS threaded barrel from CZ Custom?

I don't want to cut the slide, and even a minor inprovement will help in ringing steel faster...

 

And, would also like to give the SP01 Shadow a similar treatment (no alteration in the slide or frame), but add a comp that works with factory loads.

Edited March 24, 2020 by coolbox
Spell errors

[MoRivera]

Have you also considered shooting softer 147 rounds?  I get them (in normal times) from Fenix ammunition.  Great load for steel/plates/knockdown.  I also have a longside SP01.

 

Edited March 24, 2020 by MoRivera

[kneelingatlas]

8 hours ago, coolbox said:

 What comp for 9mm factory loads (S&B 115gr), for steel plinking, on a SP01 based long slide and the new TS threaded barrel from CZ Custom?

I don't want to cut the slide, and even a minor inprovement will help in ringing steel faster...

 

And, would also like to give the SP01 Shadow a similar treatment (no alteration in the slide or frame), but add a comp that works with factory loads.

 

Your barrel is treaded 1/2x28, right?

 

If so this would be worth trying:

 

https://stores.sjcguns.com/sjc-major-9mm-11-port-aluminum-compensator/