Airsoft Sniper Forum banner

PDI hop up adjustment screws

17402 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.


1 - 20 of 126 Posts
Alright thanks. How many times did you wrap it around? I would assume once as not much should be needed, as the screws and the hole is very small.

This sounds like a much better plan than going with the screw tightner gluey stuff :)

Were you having the same problem I had. Its been a pain in the ass for me for a while now. I thought I just was adjusting it
Dude, I did the same thing. Busted my one screw due to the fact that I had the bolt back and for some stupid reason I pulled the trigger and the cylinder head slammed into the hop up screws.

I had to get some of the PDI repair kits as the screws were all bent out of shape.

Anyways, wouldn't the tape peel as I might need to turn it one way, and then maybe back the other way later?
Ok, so I did the teflon mod. Man, those screws are just so tiny. Anyways, the first couple of times I did it, the teflon tape just all shriveled up to the top. So I did it again and now it should be in there good. Alittle came up and was hanging out, and I just used the allen wrench to take it out, but there should be enough inside to do the job. If not, I get to do it all over again yay! Wish I could test it out right now, but its too late and darkness is upon us.

P.S. I swear if I get it shooting great, and then all of a sudden shots to the right again, I will cry ::)
See less See more
Just got done testing out the rifle this morning. After two hours of adjusting, dissembling, reassembling, changing buckings, nubbings, etc. etc. still no luck.

It started off with me just tweaking the screws to adjust the hop up correctly. Then wild shots all over the place. So I checked the bucking, then decided to switch it. I literally put everything together perfectly. Everything aligned, so I thought I was ready to go. The bbs decided not to feed this time, so I took it apart again. A new problem came up when the magazine catch decided to fling a few of its pieces around. The outer barrel assembly and mag catch got stuck to the stock. After a few minutes of fiddling with that, I got that apart. So I went to work on the hop up chamber. Then the outer (largest) o ring on the hop up chamber decided to snap. So I got a new one, and final one from my repair kit. I put the inner barrel and hop up back into the outer barrel. When I slid the cylinder in, the rug on my carpet decided to stick to the hop up chamber, and got jammed up pretty good. A few minutes to get the carpet out, and I was on my way again. Went outside, took some shots, and still jamming up. So I decided to call it a day, after around 2 hours of my time, 300 rounds, and three dissembles and reassembles of the rifle.

I guess not everyday is a good day :(

Edit: I just could not quit on the rifle just yet. So I did some more tweaking, and now my magazine catch broke. I had a spare so I dropped that one in. Then the screw in the magazine catch stripped so now I have a wobbly magazine catch, that can barely hold in the magazine. Not to mention, after TWO more hours of fiddling with the rifle, I still have not solved the problem. It seems the rifle wants to fling some plastic left now, rather than to the right. :-/

Edit Edit:

Ok, two more hours of tweaking, and still sparatic shots all over the place.

Here is what I know is not the problem

1. Nubbin: I changed it four times
2. Bucking: Changed it four times as well, and its aligned correctly, no doubt there
3. BB weight: Changed it many times
4. Barrel vibration: I added a few more spacers

What might be the problem
1. Spring: This might sound odd, but after taking some shots, I noticed the consistency was not there. This is the stock spring that came with my rifle over two years ago. Maybe its worn down. Not to mention, the consistency of a clone rifle spring is probably very very bad. This could result in the sparatic shots. Each bb is propelled by a different amount of fps, resulting in inconsistent shots.
2. The hop up adjustment screws: I was pretty sure I fixed this, so I doubt this is still the problem. They are in there tight.

What to you guys think? I am leaning towards the spring. Its inconsistent fps output could cause the bbs to go all over the place.

shot 1: 387 fps
shot 2: 367 fps
shot 3: 378 fps

I do not own a chrono so these are just examples. Any thoughts on this?

Keep in mind I have adjusted the hop up in every way possible and have done this for over 30 some hours. Maybe more. Its driving me crazy. :'(
See less See more
Haha, I decided to take the next few days off after this crazyness :) It will give me some time to get an order together for some stuff I need, including some more bbs, and a new spring.

By cylinder nozzle, I am guessing that is another term for cylinder head? If so, its a laylax cylinder head that looks like its in pretty good shape to me. But I can check it out again later when I dissemble it all again.

The spring is very very old, and that is what I am thinking is the problem. It just seems to be putting out sparatic fps ranges, so that could be causing the major inconsistency.

As for the nub. I tried using the pdi nub, and when the sparatic shots occurred, I immediately thought the nub was the problem. Switched over to the scs, same thing happened. Switched back to the pdi nubbin for now. So the nub is not the problem.

Thanks for the input. At this point, its got to be the spring. Nothing else makes any sense. Heck, I even switched out the hop up arms for my spares and same thing happened.

Ill keep you posted in the upcoming weeks. It should take around 8 days for my order to come from airsoftgi, and I have not even placed it yet.

That will give me some down time. Otherwise, I see myself throwing the rifle into a lake or something :)
See less See more
Haha, safety first I guess :)

I checked the nozzle for any damage. It had alittle scrape on one side of the nozzle, so I put in the old one I had lying around. Still the same exact results. Dont worry, I did not spend three hours on it. Just trying to identify the problem so I know what I need to buy in the upcoming days here. I told myself not to try and tweak with it, as its my day off from that :)

Anyways, same results. Alot curving to the left. What makes me think its the spring is that some bbs curve left and down, and some curve left and up. Then one decides to fling itself to the right. I am guessing the different fps outputs are causing the inconsistency. I am curious to try another spring in the near future.
I was just thinking about the barrel in general. Whether it could have a scratch or something, but looky what I found:

Quote from text: No matter how well aligned your hop-up is, even if you use an SCS or other nubs, the best bucking, the most consistent bb diameter and the best barrel in the world, you will get very inconsistent groupings!
:(" title=":mad:" border="0"/>
See less See more
Actually he uses the scs nubbin in the pdi chamber. He just meant that even if you use a great nubbing such as the pdi nub, or scs nub, best bucking, perfectly aligned, etc. etc. you will still have consistency problems when you are having various fps outputs.

He got it to work by using some glue like substance. Scroll down the page.

Edit: Here is a conversation about a problem that is the same as mine:

"I've done that b4 except that i make it 4 pieces 2 for rear & 2 for front, mayb it will work. The strange thing is after i adjusted the hop up screws, the hop effect is very minimal for few shots lets say....5-6 shots & then suddenly the bbs went straight up like over hop even though i didn't adjust it. It is very weird since then as if the hop up doesn't sits properly. I think of it like a self adjust. I thought mayb the 2 screws is too loose causing it to adjust itself or the hop up lever spring that push the levers down is weak or inconsistant bbs weight. Go me puzzle at that time till now."
Snake, ive met the same problem. the screws tend to loose as you fire, dont ask me why, but they do. In my case i was geting more hop on one side (left) the more shooting ive done.
Solution: Lockite or any glue for screws will do. it worked wonders for me. The adjusting is not as smooth as it was, but it stoped geting more hop after few shots.

i hope this helps you.
They were having the same problem. So far, going with the teflon tape, it seems to work somewhat. Can't really say how well since I do not have consistent fps output. But if the spring ends up not being the problem, perhaps I just need to work on the screws some more.

On another note, the stuff on that forum is very interesting. They talk about how that little silver piece on the pdi hop up chamber comes loose which could cause turning of the hop up chamber, despite if the two small screws (not the hop up ones) are in place. Everytime I take apart my rifle, that piece is loose and sometimes not even attached. I just put some tape on the barrel next to it, to keep it from moving around. Also, how the hop up arms are a little flimsy and how there is too much room for the arms to move around. Looks like a few mods in the future are in order, and I will see how it goes.

Edit Edit

I have everything dissembled now, and am going to spend the next few days cleaning my rifle and its parts. I know vindi had a guide somewhere on how to clean your inner barrel, but I do not have access to some of the stuff he used. Woogie, what do you use to clean your barrel? I saw some stuff online, but I just do not trust some of the stuff they are doing.
See less See more
The spring is on its way right now. Its coming in an order I placed last friday. Speaking of orders, just got my new scope from Excited to get some use out of that as well.

I will be giving an update on the rifle hopefully by this weekend. Really it depends when my order arrives and if my zero trigger gets here in time. (my other one crapped on me).

As far as the barrel cleaning kit, could you give me a specific name, or should I just look around at Walmart?
Lol, sorry about that. I meant my stock trigger unit broke, and my zero trigger is on its way. :)

As for the cleaning, I will mainly take apart the whole gun and hop up when I clean it. That way I do no harm to the bucking or anything. Although that could become a pain after awhile. O well, I will wait and see how it goes.

Thanks for the help. I just got to find some more time to go and get all the necessities. ;)
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.
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.

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.... ???
See less See more
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. ;)
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.... ;)
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
See less See more
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 :)
See less See more
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.
1 - 20 of 126 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.