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Discussion Starter · #1 ·
Hey guys, i own a UTG mk96 with the following upgrades:
-455mm Prommy inner barrel
-PDI Hop Up Chamber
-Prometheus Purple Soft Bucking
-Laylax Zero Trigger
-Laylax Teflon Cylinder
-Laylax Damper Cylinder Head
-Laylax 3 Element Piston (Purple)
-Laylax Spring Guide
-Laylax SP150 Spring
The current ammo im using are Madbull 0.40g bbs

So here is my problem:

The gun in its current state is much capable of hitting targets 200+ feet however the hard part is actually landing the shot on the target. The range i have set up at my house is roughly 170 feet and thats what ive been sighting in the gun too. Now the main issue im having with this gun is its consistency. Previously, i have been running the PDI chamber completely stock with no mods and the stock, clear nubbin. At around 170ft, the shots were either right on target (Which was rare), 4 to 8 inches off target (the most common shot), or swerving so far left or right it off target it was embarrassing (1 to 2 feet). I noticed that at around 160ft, 10ft away from hitting the target, the shots either curve left or right; even up or down and the direction is always random. Just tonight i dabbled into DIY modding the chamber after looking at some threads and settled with adding a metal nub made from the piece of metal that is used as the cocking indicator in the original cylinder and shimming the hop arms. With what materials i had available, i was only able to add a shim in between the arms because the best material i found wasn't as thin as i would like to allow me to have three shims in between and to the sides of the hop arms. I added a shim at the base of the arms, attached to the axle, and one that is just slipped into place, near the front of the arms so that the spacing is the same all the way down the arms. After some test shooting, i was able to see a noticeable difference in consistency. The maximum deviance from the center of the target was maybe 4 to 6 inches at maximum and this was every shot, still the target is at 170ft. Much better than previously where the consistency was completely random from on target to way out of whack. Also since i added the metal nubbin, any form of accidental under-hop is non existent. However, this deviance from the target is still happening at around 160ft. And what i mean is that at 160ft, 10ft away from hitting the target, the bb starts to curve left or right or even a little bit upward. If a target is at 200ft or more, the curve away from the target will too great to ever hit a target at that distance. Even at 170ft, hitting my target is a challenge; i might as well stick to my aeg. So I come here to ask for advice as to how i can fix this. It's extremely aggravating to be so close and yet so far away.

Could it be that i need to just add more shims to completely reduce all play in the arms to achieve maximum consistency? My current setup could still have movement. Or maybe is it that im using a 455mm inner barrel and not the correct length of 499mm? Or even maybe my bucking?

Any help or leads to fixing something is greatly appreciated.
Thank you
 

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This is what always help me with my bar 10. I know it is stupid but bare with me. Put it your stock parts and change one at a time. Like stock part hmmm shoots good. Add new piston and blah. Or reinstall the pdi hop up and check the little o-rings.

Common mistake that can happen. The barrel is bent or the bb is hitting the barrel cap when it is leaving the barrel. And or it wobbles too much and you need to make barrel spacers.

Trying either a systema bucking or a pdi hold bucking. Those may work good. Also try madbull.
Also tries different bb brands. Sometimes guns don`t like eating that bb and will shoot amazing with a different brand.

Remeber my tactics are still retarded but you never know what you could learn. Remeber I like my karma at negative 21.
 

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Discussion Starter · #3 ·
i do like your approach but there are a few things i forgot to mention. the inner barrel as spacers all down its length so there is little vibration. ive also drilled out the barrel cap so that it has a wider exit hole so ive eliminated any bb to end cap contact.

a bend in the barrel is a possibility but with inconsistency in both directions and upward, im gonna bust that possibility. The bucking and BB combo could be a contributing factor. However, with the metal nubbin, i cant use any weight of bb under .40 because it will hop the bb. i have the hop arm adjustments at zero on my pdi chamber and miraculously its giving my .40s just a smidge of over-hop and i mean barely over-hopped. its basically a miracle but nontheless not ideal :-/
 

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I would definitely say that it is to do with the hop up chamber. I have a 455 mm barrel in mine too and the bb's are on target 10 out of 10 times.I would say try a different rubber. Or the chamber is turned a little too much to the right or left. Just try the stock chamber with .3g bbs and if it isn't curving a whole lot then the chmaber and / or the bucking is the problem. I would shave the nub off of the bucking so you get uniform contact etc. That might just be enough to fix it either. It would be nice if you watched your I's. Just a friendly reminder that we have grammar rules on this forum.
 

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Discussion Starter · #7 ·

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Discussion Starter · #10 ·
To "inthetallgrass":
The nub is in place. When I cut and shaved the nub, I made sure it was almost the same exact size as the window its in to prevent any unwanted nub movement.

To "fuzzywolly":
I've partially done the mod. Refer up to my first post and you can read how I performed it.
 

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Discussion Starter · #12 ·
Cheese Man said:
Shim your mag catch. That is the biggest issue I have seen with these things, what happens is it goes all over the place, and your shots do too.
Hmmm I've read about that once but never put much thought into it. Can you elaborate on what happens to the mag catch and how to fix it?
 

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Discussion Starter · #14 ·
Cheese Man said:
The mag catch is attached to the hop chamber, and so when it moves, the whole barrel assembly moves. Basically, just put tape on the sides of the mag catch until you can't move it any more inside the mag well.
So wrap tape around the actual mag catch itself? Electrical tape right?
 

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I only did this mod because my mag catch screw stripped. The receiver had a hex screw that kept the outer barrel in tight. So this mod was solely for keeping the mag catch itself from wiggling. I recommend getting a flat head from the hard ware store cut to size. This keeps the mag catch in tight. If you get one of those and have a hex screw in your receiver for the outer barrel, then this mod is pointless.

And the tape was installed after mag catch was placed on outer barrel and screw was tightened as much as possible (stripped so not all the way in).
 

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Discussion Starter · #20 ·
Ahhh I see now. Yea I do have a hex screw that threads into the outer barrel through the receiver to lock it in place.

As an update, I went to my buddy's house tonight, he also is my airsoft tech, and we preformed the following mods to the PDI hop chamber in an effort to have it perform the way it should:

-Six 0.1mm Gearbox shims spaced out in-between and on the sides of the hop arms, exactly like the c3 airsoft thread. The other three shims are placed further up near the hop adjustment screws to keep the spacing completely even and to eliminate all unnecessary play in the hop arms

-A stiffer spring on the end of the hop arms for two reasons 1) to put more pressure on the arms and keep them in place and 2) because we lost the stock one


-New metal nub

-Flat hop mod

-Modded the hop adjustment screws by shaving off a quarter of their original length with a belt sander allowing me to adjust the nub farther into the bucking to create more hop. The flat hop mod wasn't giving me enough hop so this is what we came up with to remedy that

The test shots were looking promising and so only tomorrow will tell the tale if our garage shopped DIY efforts were worth it
 
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