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PDI hop up adjustment screws

17404 Views 125 Replies 13 Participants Last post by  fuzzywolly
Ok, so today I decided to tweak with my rifle and installed the PCS (polar star concave spacer). I took out the pdi nubbin as I wanted to try out my pcs due to problems I was having with my hop up.

Turns out the problem is not so much the nubbin I am using, but its the screws themselves.

You see, after I adjust the hop up screws to that sweet spot it goes something like this....

-First shot: Straight, dead on, just beautiful.
-Second shot: Same as the first
-Third shot: Way right
-Fourth shot plus rest of shots: Way right

I could not figure out the problem for quite some time, and after around 2,000 bbs put through it, I think I figured it out.

I realized that when I would adjust the screws, it was way to easy, and the screws seemed loose. They would turn with just the slightest force. This brought me to the conclusion, that after a few shots, the vibration from the rifle, causes the screws to turn themselves, readjusting the hop up.

I am thinking about trying some screw tightner substance that keeps the screws from loosening up so easily. I will still be able to adjust them, but it will take alittle more force.

I want to run out to home depot or true value today, but I wanted to know what kind of screw tightner you would recommend. Keep in mind I do not want it to be too hard to adjust, just something to keep it from loosening up so easily.


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Try some teflon tape man. That is what I had to do with mine.

This way you don't have to fight with them to move them, or if you change a bucking or what not and need to tweek.
Yeah my one screw was really loose, then again I didn't tighten them up before I tried to push the bolt forward :( So my one screw is really messed up at the end and I am unable to get the allen key into it, so I am now using a pointed file to adjust it.

I just went once around the scew to get it to hold really tight. Just make sure that you wrap the tape the correct direction. If you do it backwords the tape will peel off when you adjust it. That and I suppose it wouldn't matter if you did to many wraps, as the screw holes will peel off the stuff that wont fit.
Yeah that is true as well.. hmm. .. But once it is up inside the threaded area I would think it would be ok. That and if it starts to hang down just grab a needle nose and pluck the extra out.
*Hands fuzzy a beer*

Take a few days break man. Come back when you are not so pissed at the rifle and you will work better, trust me ;)

I would say possibly the spring or the cylinder nozzle.

If the spring is old, like you said, it is probably about done. Try a new one and see what happens.

Is the cylinder nozzle nice and smooth? Or is there a burr or something at the tip? This could be causing the nozzle to scrape the ammo and cause it to fly all crazy like.

Are you still using the SCS nub? I didn't think they would work in the PDI style hopup. Try using the stock rubber tube thing, see if you get better results.
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LOL ..... well just make sure you wear a life jacket first.... lol

But yeah I was talking about the cylinder head. Because you did what I did to mine, so it could be the scrapes on the nozzle head that could be causing some problems.
I hope the spring works for ya.

Stupid question.... is the barrel clean?? I know I have forgot to do this from time to time and couldn't figure why I couldn't hit anything.
Sounds like you got her figured out now! Woo hoo
I usually just use the cleaning stuff I use for my real rifles to be honest.

I to have been thinking about making spacers or something in the chamber itself more center. That and I need to take a look at that barrel "nut" as well. As I don't have the two set screws for the sides of the chamber.

So did the new spring fix the problem?

I hope I am done with the rifle, aside from the small tweeks. Becuase now I have my M24 to play with, and to be honest.... I may switch to that rifle as a main. So if anyone wants to buy a nice L96 hit me up
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Yeah take a look around the gun department there at walmart.

I just use that because I have it laying around. Not to sure how it is for the bucking but nothing as of yet. If you want, get a small thing of Windex and use that. Should get the barrel nice and clean, and streak free ;)

And how did you get a zero trigger to crap out on you?!?!
No problem man, just let me know.

I am not 100% sure if that solvent will do any damage to the barrel or not. I am also using a Mabdull V2 barrel, it appears to not harm the barrel, but not to sure about a different barrel though. I have done it once in this barrel, but have always done it with the PDI barrel that I have. Being that it is steel, the same as a rifle barrel, no harm was imparted on that barrel.

So if anyone else is thinking of doing this..... let me say this..... DO AT YOUR OWN RISK! i AM NOT RESPONSIBLE IF IT EATS YOUR BARREL.

To be safe I would either use soap and water, or windex.
Yeah that is a good idea...

Either that or get some 550 chord and make a bore snake out of it. Cheap and guaranteed not to damage your barrel.
Yup he nailed it.

That is a quick way to clean the barrel durring a game as well. I carry one with me always.
Get a bigger screw for the chamber.

Hmmm...... that is fishy...... It may be caused by the chamber not being held in propperly, that could also be causing the miss feeds.
Are you sure all the parts are in the rifle propperly?

I know I have messed that up before and it caused all sorts of problems.

If that doesn't work you can always just buy my rifle
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I can prommise that one of my rifles will make you a better player ;)

What are you using as the nubbin? I have had problems with the stock one to be honest. I went to my local hardware store and found a replacement that works.... either that or do you do any type of plastic models? The frames that the parts come on should be just about perfect for a replacement. ;)
I think fuzzy put alot of epoxy on his to make it hold.

Either that or make your spring weaker so you don't blow the trigger out.
That is probably going to be your best bet to be honest. Just going to have to switch things around untill you get the right combo.
Sounds like you finally got her figured out.

You got her figured out as soon as I got my rifle sold
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Well it will work untill you shoot it

Have you thought about getting attaching a small spring to the back side of the arms? Then you wouldn't need to use the large o-ring at all.

I can't remember if there would be enough room or not. If not you could always sand down some groves in your outter barrel for them to work.
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Heck with all of these mods... I may not want to get out of airsofting.....

May have to grab a chepo and build it up.

I hate all of you so darn much
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