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PDI hop up adjustment screws

17401 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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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.
In that case I might stick to just using soap and water/windex. I really just need a tool to allow me to clean it. Something that I can stick in the barrel. Perhaps I should get the kit, and just use the tools included. That way I can play it safe.
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.
What exactly is a bore snake? Never heard of that before. I like the cheap part :)

And I got the new spring today, just waiting on my new trigger.
Basically It's a rope with a brush at the end of it. Pulled trough the barrel. Usually used in shotguns. Boresnakes are not good with real steal sniper rifles, cause they cant really clean all the copper. Even with a good solvent. Works wonderful with airsoft rifles tough.
Yup he nailed it.

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

Just got the zero trigger in last night. Put everything together and all the bits and pieces are aligned perfectly. One thing that is a little flimsy is the magazine catch which is connected to the hop up chamber. The screw stripped so I can only put it in so far. It makes the chamber alittle loose and flimsy, but hopefully that wont affect things too much.

Going to go test out the rifle soon. Update to come.


Not good news :-/

1. The shots were consistently shooting left. Major curves after around 75-100 feet. Some were slight curves, but for the most part, the bbs just took off to the left.
2. Misfeeds: something wrong with the bucking or something. It was perfectly aligned. Only misfed around 5 times, then it stopped.
3. All of a sudden sparatic shots, up, down, left, right. All over the place. I had no clue where the next shot would go

4. The spring guide stopper decided to fall out in the process of me pulling the bolt back. I had to take off the barrel, and readjust the the trigger box, as cylinder unit could not go back in (fell out because the spring guide stopper got too loose.

I stopped after that. Just too tired to deal with it. At this point I have learned some new things.

1. Its not the spring that is causing the sparatic shots. The new spring has caused no changes in performance.
2. I have not cleaned the barrel yet. While this could be the problem, I doubt it at the moment. Reason being the shots had been consistent to the left, until the very end. Maybe I am wrong. Still got to get a barrel cleaning kit. So we will see if that helps.
3. It could be the nubbin. I am using the pdi nubbin. It seems the inconsistency could be coming from the nubb. I will try out a guarder nub to use along with my guarder bucking.

So I have to try out a few more things yet. Kind of disappointed. What puzzles me is the fact that the shots now go to the left instead of the right. Thats the kicker.... ???
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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.
It might be. But the kicker is the fact that its now going to the left (for the most part). Before it was to the right. However, at this point you could be right. I have no clue anymore. Ill clean the barrel and change my nubbin and see if I get any better results. Updates to come.

And thanks for the input Woogie, if you are right and I fix it I'll give you a cookie. ;)
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 am almost 100% positive I am doing it right. Everything looks to be in placed. In fact, I was so cautious the last time I put the rifle together, and made sure to get everything aligned perfectly. I still think its got to do with the nubbin and barrel.

And dont tempt me with one of your rifles.... ;)
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. ;)
Yeah, using the stock nubbin (PDI nubbin). I have about five smaller nubs that come with the buckings (guarder, king arms, prommy, etc. etc.) I will give one of them a try soon. Should make a difference too. I have only used the SCS and PDI nubbin, so we will see
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woogie said:
I can prommise that one of my rifles will make you a better player ;)
That sounds like false advertisement, can you prove me wrong maybe.
Lol,just want you to know your not the only one with a problem. i got my zero trigger in today and had to send it back because it was the wrong one. So i figure i mess around with my friends in a small back yard urban game(he lives in a non trough street and all the neighbors are ok with us playing). Well any whey i put the stock trigger on and the plastic case the holds the sears in place breaks in half, does any one have any ideas on what i should do. I only ask because its going to take 2-3 weeks for my zero trigger to come back, Second I have a large game in a week from Saturday.
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.
Hidden, get your money back on the trigger from wherever you ordered it from. I think has a l96 zero trigger in stock at the moment. Depending where you live, it could be at your house by monday, and at the latest probably thursday. They ship fast.
Sorry for the double post, I want to let you guys know that I have an update :)

Ok, so I decided to put in some new things and take out some others.

What I took out:
1. pdi nubbin
2. guarder bucking: was ripped at the end; most likely was a part of the problem
3. High Hop up arms

What I put in:
1. Prommy nubbin: Way softer than the PDI nubbin. Since I am only shooting around 450 I should be good.
2. Prommy bucking (soft) (replaced the ripped guarder one)
3. Regular Hop up arms

I am hoping to see some major improvements.

Again, apologies for the double post. Just giving you guys a good ol' update. Wish me luck :)
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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.
Lets hope this works. I am losing my desire for the rifle. Despite it looking so good, it performs so bad. But I will give this another try.

Decided to finally test out my rifle since my last switch of the bucking, nubbin, and hop up arms. Started out doing some test shots with .4 madbull bbs. Shots went low, despite the hop up screws being all the way up as far as they can go. Thats a given seeing I am using the regular hop up arms, and not the high hop up arms.

Decided to go down to .28s, and see what I could do. Adjusted the screws and was getting some curve to the right. So I adjusted the one screw to compensate for too much hop on the one side. Started getting some really nice tight and straight shots.

Even when the shots were curving, I noticed it was consistent. In the same spot everytime. It all came down to just having to adjust the screws. This time, I had it in the right spot in five minutes. If I would have tried that a month ago, it would have been nearly impossible, given the fact that the shots were so inconsistent.

Turns out, the PDI nubbin was just too hard, and gave way to much hop, even when the screws were all the way in. The Prommy nubbin, which came with the soft bucking, is providing much better consistency.

I am curious to try out the high arms again, simply because I want to be able to use my .4 bbs. But thats for another day.

Thanks Woogie, for helping me out along this seeminly never ending journey to figuring out this problem. :)
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