Zbroia Kozak POI (Shroud Fix, my take)

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MACTEN

MACTEN

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Nov 18, 2020
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I encountered some POI shifts with my Kozak after getting it and found that it was because I had taken the shroud off and not tightened it to the same tension it was after sighting it in. A brief web search showed me that someone from 961 AirgunZ had done a video of his particular fix.
It involved a modification using one of the two holes in the front band that is attached to another with a pic rail on top and allows the rifle to become a semi-bullpup.
If you own the rifle and have had the issue, you have likely seen this informative video.
Some people went after the man with a few issues in comments and that maybe it was a little sloppy.
I thought it was fine but could be improved somewhat with a tap and set screw vs his small rod.
Not saying his fix was bad but whenever I see a place to tap a hole.. I'm there...
Once again, the references I make to the video are for those who have, or will watch it based on a problem you may have had with the Kozak POI shift.
The mans name is Joseph and I think he says he works for Zbroia..hard to catch as he says it quickly. Link below.
Joseph from Zbroia?
Either way I set about fixing a few issue I saw with the fix he provided.
1. Have a somewhat more solid, cleaner way to fix the shroud to the tube/barrel clamp.
2. securing the end caps (receiver end and muzzle) to the shroud so they wouldn't turn either.

I used a M3x.5 tap in the same hole he put a post in.
Filed a small notch on the cap closest to the receiver, to accept a set screw.
Epoxied both muzzle and receiver end caps to the shroud so they won't turn and will keep the exact same tension I would set.
Now there is no movement whatsoever, and with a 1.5mm Allen wrench, it comes off fairly quickly only to return exactly to the set point.
I've tested it and it's repeatable.
If you decide to do this you'll need a M3x.5 tap.
An 8mm and 4mm long M3x.5 set screws /Amazon will have them as they are common/
( the 8mm is the main set screw butting up t the shroud and the 4mm is behind it so it won't move in the hole )
There is no need for a pilot hole to be drilled as the M3 tap fits the hole almost like it was drilled for this reason.
I hope this helps out someone who has the POI issue from removing the shroud to clean the barrel, but hasn't found a tidy fix that's both functional and more factory looking.
Joseph from 961 AigunZ.. If you're in here, thanks for your insight.
Pics below.

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Zbroia7.JPG
 
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mtnGhost said:
Weird problem. Read your post but admittedly didn't watch the video.. are the tolerances just way off on the endcap?
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It's not a tolerance issue. It's just a design issue. The shroud can continue to be tightened and only stop when you decide to stop or run out of grip. When this happens it puts a lot of tension on the barrel and the barrel responds by moving slightly, chaning poi every time. By securing all points of movement and stopping the shroud from being tightened past or prior to where you had it last time.. The poi stays the same. Even if you like a really tight shroud, the barrel will always be tensiond where you decide to have it set up when you start the mod.
 
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MACTEN said:
It's not a tolerance issue. It's just a design issue. The shroud can continue to be tightened and only stop when you decide to stop or run out of grip. When this happens it puts a lot of tension on the barrel and the barrel responds by moving slightly, chaning poi every time. By securing all points of movement and stopping the shroud from being tightened past or prior to where you had it last time.. The poi stays the same. Even if you like a really tight shroud, the barrel will always be tensioned where you decide to have it set up when you start the mod.
Click to expand...
Running out of grip isn't an issue if you use a strap wrench, then the opposite is true! 😁
 
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Vetmx said:
My Hortitsia had the same issue. I chose the quick easy route and just torque my shroud to 20 inch pounds. No drilling, tapping or notching. Couldn’t figure out why my gun would act so weird until someone posted that video a while back.
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Tapping it took about 5 minutes and no drilling was needed. Good to hear you figured yours out. If the threaded area was at the rear instead of the front this wouldn't be an issue.
 
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I would clean my barrel then put the shroud on and it shot ok. Polished the barrel and then it shot horrible. Vented the shroud and it shot great. Thought ok the venting must have helped. No, the barrel, gun and settings were always fine. It was the different torque I screwed the shroud on every time that had me spinning in circles. Isn’t it crazy that such a stout barrel can be manipulated that much by the shroud tension. I never really cranked it on like the guy in the video. He was twisting it like he hated it. I was just being inconsistent.
 
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Vetmx said:
I would clean my barrel then put the shroud on and it shot ok. Polished the barrel and then it shot horrible. Vented the shroud and it shot great. Thought ok the venting must have helped. No, the barrel, gun and settings were always fine. It was the different torque I screwed the shroud on every time that had me spinning in circles. Isn’t it crazy that such a stout barrel can be manipulated that much by the shroud tension. I never really cranked it on like the guy in the video. He was twisting it like he hated it. I was just being inconsistent.
Click to expand...
So, from when it developed a touch or resistance, how much more did you go? What were the symptoms? I'm having issues with my Sapsan, might be the same problem or I messed up the barrel, a really good possibility.
 
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Vetmx said:
I would say if you grab the shroud to tighten it, you’re already screwing up. 20 inch pounds is probably as tight as you could make it just using your thumb and forefinger. Remember with any gun that has a tensioned barrel, you’re not trying to stretch it.
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Explains why I've now got a 700 mm barrel. :LOL:
 
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hogkiller, that explains a lot, for a 550mm barrel,,, ya over stretched the barrel and it narrowed the bore,,,o_O:ROFLMAO:, watch out for him, Vetmx, he is a known hogkiller
On the serious side, now
Hogkiller, I had a little burr inside of my Sapsan barrel, at the crown when I first got it, the burr was from the crown tooling @ Zbroia, it was a light burring that I removed with a rubberized bit that was smaller than the bore,,, I dragged the burr out by hand. (I forgot to tell ya about it), found it using Q-tips.
It threw my pellets like a shotgun

I must be lacking understanding about this shroud modification, I fail to see how it does jack squat,,, but the amount of torque that a person uses, DOES AFFECT IT.
I get the impression that the Joesph @ zbroia is a retailer rather than a factory employee, I could be mistaken

the thing that gets warped easily is the baffle insert, you are tensioning it also,, light weight aluminium

right now today I am shooting without the insert and shroud on my Sapsan, w/moderator on the barrel,, my Kozak is a different story, I still use the shroud on it, with the baffle insert and a Donny tatsu
I just hand tighten it like an old man with arthritis,,, not to tight








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jarmstrong said:
I must be lacking understanding about this shroud modification, I fail to see how it does jack squat,,, but the amount of torque that a person uses, DOES AFFECT IT.
I get the impression that the Joesph @ zbroia is a retailer rather than a factory employee, I could be mistaken

the thing that gets warped easily is the baffle insert, you are tensioning it also,, light weight aluminium

right now today I am shooting without the insert and shroud on my Sapsan, w/moderator on the barrel,, my Kozak is a different story, I still use the shroud on it, with the baffle insert and a Donny tatsu
I just hand tighten it like an old man with arthritis,,, not to tight








9
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Hi Jack! The squat is the fact that when you tighten the barrel shroud, because it's threaded on the muzzle end and butted up to the barrel/cylinder retainer, it pulls the barrel... Not making it longer but moving it slightly one way or the other. The barrel is then being tensioned. There is nothing wrong with tensioning the barrel but if it isn't tensioned the same amount every time you can get POI shift. It happened to me and others obviously. Fixing the shroud to one location doesn't stop how hard you tighten it, it stops you changing how hard you tighten it giving the same tension every time. And there it is.
 
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jarmstrong said:
MAC, ya confuse me,, my shrouds are not threaded, they are just straight tubes,, the baffle inserts are threaded on to the barrel the baffle insert pulls on the barrel and pushes against the end of the shroud.
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I'm sorry to confuse you. I didn't invent this wheel just tried to improve upon it with a M3 screw. The baffle insert is threaded to the barrel,, When you tension the barrel to the baffle insert the whole barrel shroud assembly (shroud, baffle,) is pulled by the baffle/shroud end where it's threaded to the miuzzle and cap that holds it in the shroud, then pushed at the breech end. Nothing is perfectly concentric on either end so the barrel moves slightly. If the baffle (threaded), wasn't in there it would do the exact same thing.
 
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jarmstrong said:
hogkiller, that explains a lot, for a 550mm barrel,,, ya over stretched the barrel and it narrowed the bore,,,o_O:ROFLMAO:, watch out for him, Vetmx, he is a known hogkiller
On the serious side, now
Hogkiller, I had a little burr inside of my Sapsan barrel, at the crown when I first got it, the burr was from the crown tooling @ Zbroia, it was a light burring that I removed with a rubberized bit that was smaller than the bore,,, I dragged the burr out by hand. (I forgot to tell ya about it), found it using Q-tips.
It threw my pellets like a shotgun

I must be lacking understanding about this shroud modification, I fail to see how it does jack squat,,, but the amount of torque that a person uses, DOES AFFECT IT.
I get the impression that the Joesph @ zbroia is a retailer rather than a factory employee, I could be mistaken

the thing that gets warped easily is the baffle insert, you are tensioning it also,, light weight aluminium

right now today I am shooting without the insert and shroud on my Sapsan, w/moderator on the barrel,, my Kozak is a different story, I still use the shroud on it, with the baffle insert and a Donny tatsu
I just hand tighten it like an old man with arthritis,,, not to tight








9
Click to expand...
I inspected the crown, the basic bore looked fine, BUT the crowning looked uneven, THAT would cause the issue. I didn't give it a good inspection but tomorrow that puppy is getting a full blown check out. My old barrel that cost me $200 should be here tomorrow,
 
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