The Original CZ Forum
CZ LONG ARMS => CZ Scorpion EVO => Topic started by: Rooftop Korean on July 13, 2019, 12:00:45 AM
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Hello everyone,
Wondering if anyone out there has a similar issue as myself. I did a search but haven't found anything on this forum. When I first shot my Scorpion I found while using the iron sights that it shot very low. Point of aim and point of impact was about 12" low at 50'. I tried to adjust the front sight post to the bottom stops but my point of impact was still about 10" low (If I remember correctly). So I decided to sight in my red dot sight which needed a considerable amount of elevation adjustment.
So at home I decided to have a look at my HB Industries hand guard and this is what I found. I laid a ruler against the receiver and found that the end of the hand guard at the muzzle end was about 1/16" low. Then I looked through the Mlok slots and it looks like the barrel is lower than the rail.
(https://i.imgur.com/FaDoV7i.jpg)
(https://i.imgur.com/SuyQGkB.jpg)
Eyeballing the barrel and hand guard isn't the most accurate way to check barrel alignment but I think there may be a slight issue here. With the combination of the hand guard and barrel's slight misalignment I estimate that there may be up to a 1/8" muzzle deviation from the receiver's picatinny rail. Has anyone else experienced this and is there a way to fix this? Or is it just my mind playing tricks on me?
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Using the MBUS for 9mm will cause you to bottom out the elevation, since they are designed for 5.56. I ran out of elevation when I used them on my MPX. I stick with CZ factory sights on my Scorpions.
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Same result with the stock CZ factory sights. I got the MBUS sight s because I’ll be SBRing this piece with an ACR stock. Can’t use the CZ sights with the ACR stock because they’re way too low. Maybe I should just run it without any kind of irons or get a new hand guard that’s more in line with the receiver.
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Well, so far after some more research I saw a few threads on a AR15 forum and one here. Looks like some people had some barrel / Trunnion that were installed incorrectly. Some look like the barrel wasn’t up to par. I will do some other investigating and see what I find. Hopefully my experience will help someone down the road.
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FYI they do this with the factory handguard as well. The receivers on these guns all vary greatly as to which way they are banana'd.
You should be trying to zero at 25yds~75ft, as 50 is a little close.
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I agree that 50’ is a bit close, but that’s the limit to my local indoor range. I still think a 10” point of aim / point of impact is pretty significant though when it comes to the front post iron sight at it’s absolute limit. It shouldn’t be that bad.
I plan on stripping down my Scorpion down to the receiver / barrel assembly and check alignment. Then most likely completely disassemble and check if there’s anything I can do to realign the trunnion to the receiver. I hope it’s something as simple as uneven torques applied to the receiver halves. If not then hopefully shims may be the answer if that’s even a possibility. Then there’s bore / thread concentricity when I pick up my 9mm suppressor later on down the line.
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I noticed you have the Sapper handguard...
Mine was zero'ed from the factory and only needed some tweaking at 25 yds.
I installed the Sapper handguard a week or so ago and finally got out to the range this morning...I bottomed the front sight out and it's still about 4" low at 25 yds.
I haven't laid a straight edge across the receiver/handguard yet...I'm curious to see the results.
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I agree that 50’ is a bit close, but that’s the limit to my local indoor range. I still think a 10” point of aim / point of impact is pretty significant though when it comes to the front post iron sight at it’s absolute limit. It shouldn’t be that bad.
I plan on stripping down my Scorpion down to the receiver / barrel assembly and check alignment. Then most likely completely disassemble and check if there’s anything I can do to realign the trunnion to the receiver. I hope it’s something as simple as uneven torques applied to the receiver halves. If not then hopefully shims may be the answer if that’s even a possibility. Then there’s bore / thread concentricity when I pick up my 9mm suppressor later on down the line.
There isn't really anything you can change in regards to alignment. The way the receiver clamps the trunnion can't be changed. What do you plan on re-torqueing the receiver bolts to?
If you remove the handguard and put just the gun on a flat stone you'll probably notice it bows in the middle. With the factory handguard on it will likely look like the Sapper.
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It's not the gun. It's physics.
Flip up AR15 sights were designed for AR's, whose front post sit about 2-1/2" above the center of the bore. Since they sit up so much higher, what that does is push the poa/poi a lot lower on guns whose barrels do not sit the same distance because they were not designed to have that much adjustment.
If you can't adjust the front sight enough to zero it with the front post bottomed all the way out and you're still shooting low, you'll either need to start filing the top of the front post off, or switch to a more appropriate iron sight.
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It's not the gun. It's physics.
Flip up AR15 sights were designed for AR's, whose front post sit about 2-1/2" above the center of the bore. Since they sit up so much higher, what that does is push the poa/poi a lot lower on guns whose barrels do not sit the same distance because they were not designed to have that much adjustment.
If you can't adjust the front sight enough to zero it with the front post bottomed all the way out and you're still shooting low, you'll either need to start filing the top of the front post off, or switch to a more appropriate iron sight.
I was having the same issue using the original CZ sights.
Just went and checked my Sapper handguard...
(https://pbase.com/kwb377/image/169491058.jpg)
Between this and having to file the bottom M-Lok slots because they weren't in spec (too narrow), looks like this was a $50 hard lesson.
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I’m getting the same results with the stock CZ iron sights and the Magpul Mbus Pro sights. With the CZ stock iron sights and the Magpul Mbus sights I’m getting a 10” a 12” difference between point of aim / point of impact. Both are yielding the same results with the front sight post at the lowest mechanical setting. I don’t think it’s the iron sights.
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There isn't really anything you can change in regards to alignment. The way the receiver clamps the trunnion can't be changed. What do you plan on re-torqueing the receiver bolts to?
If you remove the handguard and put just the gun on a flat stone you'll probably notice it bows in the middle. With the factory handguard on it will likely look like the Sapper.
I plan on re-torque to 15” pounds on all received screws. I heard factory specs were 18” pounds. I’ll lay it out on a flat surface to see which way my Scorpion is biased towards.
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Ok, so this is what I found so far. I disassembled my Scorpion down to the Barrel and Receiver assembly and took some measurments by placing a straight edge on the top of the receiver and checking the differences between the muzzle end and chamber end with a square. My measurements indicated that the muzzle end is lower by 3/64" using my non scientific method which doesn't really say much. So I took the halves apart and found that the fit between the Trunion and the receiver halves are very close. Nothing can really be done without taking a big risk and turning it into a expensive paper weight. I know the left halves are available for purchase and the right half is not. So I reassembled the receiver using 15 inch pounds with loctite on each screw and put it all back together with the exception of the hand guard and the left side sling loop. I got tired of scraping my hand on it when operating the charging handle. If anything I'll install a Magpul Mlok QD on the handguard.
What I did with the HB Industries hand guard was sand down the one end at an angle to level out the hand guard with the receiver's picatinny rail. Started with #80 grit to get it roughed in then test fit it to the receiver till it worked out. Then I stepped it all the way up to #1200 grit.
(https://i.imgur.com/q9oijWQ.jpg)
It didn't take much to shape the end of the hand guard, and polishing it off with the finer grits was pretty quick work. If you decide to try this out, proceed with caution and at your own risk! Then again it's a $50 part. I wanted to save this part because I think it just looks so cool and I agree with others out there making the Scorpion look like a HK UMP.
Here's the end result. I decided to move the C-more sight to the back because it kept on interfering with my HK slap technique. Something I've been perfecting for may years with airsoft guns. The irons are there purely for backup and the placement is similar to what some people do with their handguns utilizing a RMR and irons. I'll be taking Anya to the range tomorrow with hopes that correcting the handguard will fix my sight alignment problem and that my sight configuration will be feasible.
(https://i.imgur.com/1PPXsqe.jpg)
Wish me luck!
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Has anyone contacted Pakse or HB Industries to see if they are aware of the alignment issue with the Sapper Handguard? I put one one last week but haven’t been to the range with it yet. My eyeball micrometer accurate to +/- 1” doesn’t notice any alignment issue on the top rail between the receiver and the handguard but that doesn’t mean there isn’t an alignment issue either. I left my red dot on the receiver during the change out and the dot was about 4 clicks to the right of the front sight post but the elevation was good to go.
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I haven't contacted HB Industries yet. I like to have all my ducks in a row before I contact a manufacturer / company. Me, I had to adjust my C-More and Holosight in elevation quite a bit. Windage just needed some minor adjustments.
When I test fire it tomorrow I'll send them my findings. I hear nothing but good things about HBI, and I like to make a awesome product better if I can.
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My HBI 4.25" handguard fits the same way. The suppressor still fits inside and I am able to zero at 12 yards. The gun runs so I just don't worry about it.
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Well, I went to the range to zero my EVO SBR with the new Pakse handguard and ran into the same problem the OP did. After bottoming out the CZ OEM front sight I was still super low. I put the OEM handguard back on and got back to zero. Very disappointed because this is a neat handguard at a competitive price point. I’ll contact HBi and see what they say. At worse I’m out $50 but hopefully HB will suspend sales and see if there is a fix.
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We have noticed that (by design) the Evo handguards can be sensitive to barrel nut torque; meaning that if you exceed 10ft*lbs of torque on the barrel nut the handguard itself can begin to deform in compression at the barrel nut interface. Note that the factory barrel nut is not tight with "high torque" but rather "thread locked". The intent is simply to hold the handguard in light compression against the upper receiver. Again, 10ft*lbs is the MOST that should be applied.
The factory pistol handguards seem less susceptible to sight elevation issues due to variance in barrel nut torque because the angle/1913 rail positions the front sight much further away from the barrel nut interface; versus the Sapper handguard where the sight is positioned directly over the barrel nut.
While we have been able to zero all of our test Evo's on factory iron sights without issue, with the variance possible in mating 3-4 large molded parts together like this... like they say anything is possible. We figured we would post a couple basic pictures here to attempt to show typical "squareness" of the Sapper handguards:
This geometry is very important, that the receiver be square to the top 1913 rail:
(http://hbindustries.net/store/wp-content/uploads/2019/07/IMG_1428.jpg)
And of course that the 1913 rail is straight/parallel
(http://hbindustries.net/store/wp-content/uploads/2019/07/IMG_1431.jpg)
(http://hbindustries.net/store/wp-content/uploads/2019/07/IMG_1430.jpg)
The only potential issue that we can find (and maybe what @Rooftop Korean had done earlier in this thread) is that there can be some mold flashing left around this pocket:
(http://hbindustries.net/store/wp-content/uploads/2019/07/IMG_1429.jpg)
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Also... speaking on behalf of everyone here at HBI... we here to stand behind our customers 100%. Does not matter where you bought the product or how long you have owned it... we will do everything we can so support our customers. In situations like the ones in this thread we are most concerned with determining the root cause of any issue.
Even if you have modified our parts, we are still interested in knowing the "why" in hopes that we can either improve our products or instructions. I think everyone on this forum has "modified" parts before... that is probably why we are all here ;)
Please never hesitate to call/email/message us with any questions or if you need any help with install or want pictures, measurements, additional info, etc...
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I installed per instructions, hand tight plus 1/8” turn and encountered the issue where I cannot zero the gun. I really like the handguard but it seems way to sensitive to instructed or even minor overtightening. I didn’t use a torque wrench but I can tell you I did exactly as the directions stated because I was afraid of overtightening going into this project having removed my factory handguard in the past. It looks good and is priced right but some tweaking to strengthen it for regular installation may be needed. I also found the bottom Mlok to be out of spec as well but didn’t modify it.
What I am confident in is that HBi will make things right by its customers. Maybe an aluminum one is in my future because I really liked the looks of the Pakse.
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Just checked mine on a glass table and it's even.Took it out on the weekend and it was pretty close to zeroed also.
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"The factory pistol handguards seem less susceptible to sight elevation issues due to variance in barrel nut torque because the angle/1913 rail positions the front sight much further away from the barrel nut interface;"
That explains why CZ angled the front of the factory handguard.
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I installed my Paske Hand guard per the manual. The method I used was to hand tighten then go an additional 1/8 turn every time. So far I've done this procedure about four times for troubleshooting and fitting the hand guard to the receiver. I basically shaved the back end of the hand guard at a very shallow angle. I fitted the hand guard to the receiver per the manual and checked the flatness of the hand guards picatinny rail to the receiver's picatinny rail. When I finally got it flat I figure the angle I shaved off is about 1.5*. In other words the picatinny rail is 1/16" shorter and the bottom of the hand guard is the same original length.
I took it to the range today and this is the result with Magpul Mbus Pro sights. The front sight is still at it's maximum setting but it's much better than it was. I'm sure if I used the Original Scorpion sights then point of aim / point of impact would be the same.
(https://i.imgur.com/8rUfcUe.jpg)
@ 50'
I then put the C-More RDS back on and placed the Mbus Pro rear sight in front of the Red dot sight. I aimed for the head and the grouping was decent with my novice shooting skills.
(https://i.imgur.com/t5I7NUG.jpg)
@ 50'
Thank you HBi for your interest in this thread. I didn't want to contact you guys until I fully understood what was going and a range report. I hope my experience helps you and anyone else out there.
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I had emailed HBI this weekend with a heads up to the issues and got a reply earlier today, then saw their response here also. I really appreciate their help and responsiveness.
I just went and checked the Pakse handguard (it's off the gun) with a straight edge, and both the rail and the rear edge that interfaces against the receiver were both straight. When I originally installed the Sapper, I tightened the barrel nut finger-tight snug against the handguard, then added 1/8 turn or so with the wrench.
I had reinstalled the factory handguard, so I placed the straight edge along the top rail on it and discovered it has a slight downward slant also (although not nearly as pronounced as the Pakse).
Not sure if the issue is the handguard being highly sensitive to barrel nut torque or if the front edge of the receiver isn't plumb.
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I had emailed HBI this weekend with a heads up to the issues and got a reply earlier today, then saw their response here also. I really appreciate their help and responsiveness.
I just went and checked the Pakse handguard (it's off the gun) with a straight edge, and both the rail and the rear edge that interfaces against the receiver were both straight. When I originally installed the Sapper, I tightened the barrel nut finger-tight snug against the handguard, then added 1/8 turn or so with the wrench.
I had reinstalled the factory handguard, so I placed the straight edge along the top rail on it and discovered it has a slight downward slant also (although not nearly as pronounced as the Pakse).
Not sure if the issue is the handguard being highly sensitive to barrel nut torque or if the front edge of the receiver isn't plumb.
I’m running a barrel cooler on my EVO so the barrel nut tightens against the plastic washer, then the hand guard, and then against the cooler so there is more support there than just the nut against the Pakse hand guard. If the hand guards are that sensitive to barrel nut torque then they are going to be continually problematic. I wonder if the aluminum hand guards are better at controlling rigidity during barrel nut tightening.
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I pulled mine apart again today to investigate further.
After disassembly, I mounted the receiver in a vise and used a small bubble level to ensure the top rail was level. I slid both the factory and Pakse handguards onto the gun and held them flat against the receiver face...both were straight according to the bubble level.
Then I figured out the issue...using the level on the barrel, I discovered mine has a slight downward cant in relation to the receiver. Before installing the barrel nut, the handguard indexes off the front of the receiver and is level. Once the barrel nut is installed and tightened, it pulls the front of the handguard downward. I may try and relieve some material from the channel the barrel nut resides in to see if that will allow the handguard to angle up ever so slightly.
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I also found that the barrel is canted down enough to cause aiming issues. Sanding down the receiver end of the hand guard at an angle fixed this for me. The risk here is removing too much material or uneven shaping of hand guard. It is working well for me.
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I tried sanding, but each time I reinstalled the barrel nut it pulled the front of the handguard back down.
I don't really use the iron sights that much...I'll just live with the issue until the HBI FDE aluminum handguards come back in stock.
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They can have the same issue.
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I’m having the same problem. My barre is canted downward. Have tried Sapper and Manticore transformer with same results. I completely disassembled today and it looks like with just the barrel in the receiver it is canted WAY down. It’s like the front of the receiver at the trunnion lugs isn’t square. I have no clue how to go about fixing this.
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They can have the same issue.
I was under the impression that the HBI aluminum handguards were free float and did away with the barrel nut?
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HBI aluminum doesn't use the 18mm barrel nut.
https://www.youtube.com/watch?v=Q-Dny1zPZZg
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They can have the same issue.
I was under the impression that the HBI aluminum handguards were free float and did away with the barrel nut?
The issue is that the barrel is angled down slightly, because of the receiver, and the HBI handguard attaches to a device on the barrel. I sent a pic to HBI and they said that the receivers have not been very precise. My aluminum HBI handguard is canted down slightly.
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HBI aluminum doesn't use the 18mm barrel nut.
https://www.youtube.com/watch?v=Q-Dny1zPZZg
I'm aware as I have one installed. I could post what HBI told me if that would be helpful for you
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Yeah I have tried several handguards. The issue is the receiver. It isn’t square up front and that is causing some of the barrels to be angled down. It’s a simple blowback so I guess life goes on, but once you see it....you just sort of always notice it. No real way to fix it either. If you sand and square up the front, then the trunnion bosses become smaller in dimension and the barrel will have play. I have looked at and played with mine in the shop all day. I don’t see a good way of fixing it.
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Shorten the front sight post?
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I personally think if you’re looking for close to perfect, this isn’t the firearm for you. If you’re looking for something with a lot of personality, really fun to run with and don’t mind a slightly pigeon toed firearm then the Scorpion is for you. I work with what I have and shortening the front sight post is something I’d do to work this out if I had to.
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HBI aluminum doesn't use the 18mm barrel nut.
I'm aware as I have one installed. I could post what HBI told me if that would be helpful for you
I was replying to kb377
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I personally think if you’re looking for close to perfect, this isn’t the firearm for you. If you’re looking for something with a lot of personality, really fun to run with and don’t mind a slightly pigeon toed firearm then the Scorpion is for you. I work with what I have and shortening the front sight post is something I’d do to work this out if I had to.
There a difference between having personality like the safety stabbing you in the finger and having a limp barrel. I can't believe the let them out of the factory that way.
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There a difference between having personality like the safety stabbing you in the finger and having a limp barrel. I can't believe the let them out of the factory that way.
Sort of my line of thinking. As a realist, I understand that this is simple blowback clamshell design. Heck, like 6 hex screws and you can literally turn this thing into a pile of pieces. However, as a consumer, this is marketed as a quality PDW. I have many CZs, and I have even been to the factory in the Czech Republic. My handguns and Brens are of unflinching quality. I guess I expected as much from the Scorp. Cest la vie.
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There a difference between having personality like the safety stabbing you in the finger and having a limp barrel. I can't believe the let them out of the factory that way.
I feel you there. I find it funny that CZ "listened" to their customers by threading the barrel to 1/2 x 28, and stopped welding the trigger pack to the lower. Then they never redesigned the grip and right safety which are probably the biggest complaint they get. I would probably say that it's probably cheaper to thread a barrel, and goop on some thread locker, than re-tool molds for a grip and produce a separate mold for the right side safety.
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I find it funny that CZ "listened" to their customers by threading the barrel to 1/2 x 28, and stopped welding the trigger pack to the lower. Then they never redesigned the grip and right safety which are probably the biggest complaint they get. I would probably say that it's probably cheaper to thread a barrel, and goop on some thread locker, than re-tool molds for a grip and produce a separate mold for the right side safety.
I'm glad that CZ has been listening to their customers and giving them what they want. That tells me that they're striving to improve the product. Which is more than many US gun companies are doing now, who are doing nothing more than riding the coat-tails of old designs that have been around for half a century.
I have noticed that many of the guns on the market today are not even US made products anymore.
As for cheaper to thread a lot of barrels than to make a new mold for the right side safety, I would strongly disagree. Speaking as someone who does have a lathe and can thread barrels and knows a little about that, there is a lot of time in setup and tooling costs involved in it. Not even taking into consideration having the skilled labor to do quality work, which CZ is known to do.
The ambi selector switch is a lot easier for the end user to do something with themselves if they want, than to be able to thread their own barrels when they get them home.
It's just a poor comparison I guess. But, CZ started out importing a pistol. Then a carbine. Now there are probably about a half dozen different models if you take into account the restricted SMG and Integrally suppressed models.
I am confident in saying that CZ has been striving to make a good product and one that people can rely on. With as many people that like the scorpion (and CZ in general), they have a strong following from their customers.
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As for cheaper to thread a lot of barrels than to make a new mold for the right side safety, I would strongly disagree. Speaking as someone who does have a lathe and can thread barrels and knows a little about that, there is a lot of time in setup and tooling costs involved in it. Not even taking into consideration having the skilled labor to do quality work, which CZ is known to do.
The ambi selector switch is a lot easier for the end user to do something with themselves if they want, than to be able to thread their own barrels when they get them home.
It's just a poor comparison I guess. But, CZ started out importing a pistol. Then a carbine. Now there are probably about a half dozen different models if you take into account the restricted SMG and Integrally suppressed models.
I am confident in saying that CZ has been striving to make a good product and one that people can rely on. With as many people that like the scorpion (and CZ in general), they have a strong following from their customers.
Ah, I thought it would be easier to thread a barrel on a factory line just because everything is already set up and would add one more thing to be done on the lathe. I totally understand the work involved when the end user decides to thread a barrel with set up as you said. I also don't see a big deal with the right side safety. It really isn't that hard to change out.
I also agree that they have done much more than other companies as far as listening to customer feedback.
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I forgot to come back and update this thread...just wanted to publicly thank HBI for their outstanding service. They got in contact with me on their own and remedied the issue with the Sapper handguard beyond my expectation.