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Tanaka AICS HopUp Problem

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Bought myself a Tanaka M700 AICS.

Built in all the stuff I had for my Tanaka M40A1 (there's a Thread around here somewhere).

I'll just put in a short list:


- Aluminum HopUp chamber so it can take AEG Barrels (self made)

- 6,01mm 650mm DBC Barrel

- Bolt with Steel Cocking Piece and self made nozzle out of plastic and G&G Striker Spring

- G&G Plunger and Knock Arm in long mag


Ok here is my problem:


When I shoot my Tanaka the HopUp just doesn't make the BBs spin. Even if turned right in, the BBs don't spin UP at all. They just go slower and fall earlyer as if the HopUp just slows them down...

Now luckily I have a Tanaka M40A1 and a KJW M700P to switch parts and find the source of my problem.

So that's exactly what I did.

I took the original KJW HopUp chamber and used a MadBull 6,03mm barrel. didn't change a thing

I took the KJW HopUp chamber and used the DBC 6,01mm barrel. didn't change a thing

I tested .23gr BBs and .43gr BBs... no difference

I tested several HopUp buckings

I tested several nozzle lengths and types (plastic, metal)


The only thing I haven't tried yet is the original bucking with original barrel. Even if that would solve the problem. I wouldn't be happy... because that would make my 6,01mm barrel and the self made Aluminum HopUp chamber useless...


The only solution that I still have, is that the buckings are to new and just don't have any effect on the BB yet... But I think it's rather strange... even a really new HopUp should work a little or not??? In my case they bucking doesn't even have any effect AT ALL!


This is really killing my motivation of making a Gas Sniper Airsoft that is reliable at 100m (300')... Because I KNOW, that with the parts and tuning I am doing to the rifle, it WILL be able of doing exactly that!








Now the thing is:

I read a really interesting Thread quiet a while ago wrote by some guy called Wupjak (I think he works together with Mike from Right Hook Fabrications... but whatever...)

He was one of the guys that went through all this HPA tuning and all the rest and he was kind enough to right it all down into some forum.

And he was recommending NOT to use the HopUp at all once you're going with HPA. He figured that now HopUp at all would make the BBs trajectory more stable...

Now I will be using HPA very soon (still going with CO2, but just can't stand the amount of O-Rings it keeps freezing and so making the system leaky).

But without HopUp you wouldn't be shooting a straight trajectory anymore... you would have to lob the BB (quiet extremely I imagine). Would do you guys think about that theory?


Well if I can't get the HopUp to work then I'll try going without and lobbing...

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The point that sticks out to me the most is the homemade nozzle. Are you sure it isn't pushing the bb past or right underneath the hopup nub? That would account for the issue showing up with the different barrels and chambers.



Wupjak was around here ages before I got started in gas rifles and it's his information that got my started on the basics of gas rifles. He is correct but with one caveat. Hopup's were invented to add extra range not extra accuracy. Turning the hopup all the way off will in fact give you better accuracy. However, your range will be roughly cut in half. You would need to increase the power of your shots to compensate for the loss of a magnus effect (backspin causing lower pressure) on the bb to make up for that but at the same time would put you over the fps/joule limits of most areas.


Since gas rifles have superior click adjustment for their hopup the idea to mark a specific point of hopup for long shots and turning off the hopup for most other short range shots has merit. However, the amount of practice needed to be proficient would be much greater and most players don't practice enough as is.

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Well it can't be the nozzle... I just checked that... it pushes the BB exactly in front of the bucking... (maybe that is the solution though - I mean can it be, that the BB needs some acceleration BEFORE it touches the bucking?)

But I cleaned the barrel and the bucking this evening and found out that there was a lot of greasy, blackish, dirty something in there... That might actually have solved the problem... But sadly enough it's dark now (2230PM in Belgium) so I can't see the BBs fly. I'll let you know as soon as I can...


But I don't want to be negative... but somehow I'm doubting that this is the solution to my problem... Well... we'll see...






Well as it seems, all the greasy, blackish, dirty something in my barrel and HopUp were the source of the problem!

I'm still not absolutely 100% sure, because it was really hard to see the BBs fly here because the weather wasn't really ideal... But I'm quiet sure to have seen some BBs flying crazy high right out of the top of my scope...

The other solution could have been, that I had the HopUp to far in... and so it didn't give the BB any spin at all... it just slowed it down seriously... But I'm not quiet sure about that theory though.

Edited by foppo

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Firstly: Sorry, for double posting. But I wanted to bring the Thread back up a little.


Now I would like to discuss about Wupjaks idea of not using any HopUp at all.

As we all know, HopUp was invented to increase the range of an Airsoft rifle by giving the BB a backspin.


Now I noticed, especially for us snipers shooting at longer ranges than others out there, the HopUp is a real issue. Even on a windless, sunny, perfect day, HPA rig (±3fps), a DBC 6,01mm barrel and good BBs the BBs will fly all right. But at a certain distance (let us say about 80m - 260 feet) the BB will spin of slightly to the right or the left or go higher or lower.

I know some rifles will have this effect at a shorter or little further distance, depending on the parts that have been upgraded, added. BUT I think I can say this without any doubt:

With ANY rifle this effect happens...


It is the HopUp. No matter what kind of HopUp we use, no matter what Bucking... this effect is just unavoidable.


Now my theory is: Not using any HopUp at all and 'tilting' the barrel inside the outer barrel.

Now I haven't tried this yet. But imagine if one could zero the rifle at, lets say 60m - 200feet. Would the BB fly much more consistent and would it be influenced fare less than when the HopUp is touching the BB?

How far would one have to 'tilt' the barrel inside the rifle?

What kind of range would be possible?


I know that one wouldn't be able to see the BB flying in there scope so easily any more. But if I point my crosshairs at a certain point at 60m and pull the trigger and SEE that the BB actually hits the point I am aiming at... well who cares seeing the BB or not then?


I don't know if this is a good idea or not... But I think it's worth trying in any case!


Tell me what you think and if you have ever tried this or are planning on trying this.

Edited by foppo

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Tilting the barrel wouldn't have any effect on trajectory if you aren't applying hop (you could fire the gun sideways and it would perform just the same as if you were to fire it right side up).


It is true that you're always going to have problems where the BB loses most of its inertia and the spin of the hop overtakes the BB's trajectory, but you have to remember that you're going to have that no matter what. What matters here is how far you can push the BB before that happens. Some systems work better than others (for example, hence the conversion kit for Tanaka rifles to use VSR buckings and barrels, or the PDI hop chamber for the Type 96 that allows for the use of AEG style buckings and barrels - both of these kits allow for a greater degree of accuracy and precision [the scientific kind, not the shooting kind] than the systems that they were designed to replace).

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Tilting the barrel wouldn't have any effect on trajectory if you aren't applying hop (you could fire the gun sideways and it would perform just the same as if you were to fire it right side up).


Sorry for the word 'tilting'. It's not the right word for what I mean...

I ment shooting the gun in an angle. And for not having to aim far to high I would install the barrel in an upward angle in the rifle. So I would see the BB fly straight up out of my scopes field of view and watch it come back down at a certain distance. Angle the shot.


I use a custom HopUp chamber that allows installing AEG barrels and Buckings btw.

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Foppo, using no hopup would be fine for target shooting or just plinking at targets but not for gameplay against other people. Our little plastic bb's lose inertia as Vulrath mentions, over time and with air drag. In order to compensate we would have to crank up the fps and use heavier ammo to reach the same distances without the hopup. That's a big NO GO.


I can understand for short distances wanting to do this as the trajectory would be very controlled. But the longer shots would require the hopup and there isn't getting around that while staying in a safe fps range. On top of that you would need to learn the trajectories of two different settings. And lets face it, we don't get as much range time as we would like. Most people's "practice" is actually in game or pre/post game when they have some free time. That's more hassle than it's worth. It's just better to tune and maintain the current system and hone our fieldcraft.


Now there has been some talk by the Polarstar guys about resurrecting the LRB design for sniper rifles. That didn't use a hopup but the curved barrel caused the backspin along it's entire length. I'm a bit skeptical on it as classic airsoft guns that do have those are pretty inaccurate although they have great range.

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You don't need to angle the barrel, just the scope. RS scope rails on some sniper rifles are angled for just this reason. Essentially it allows them to aim further without the round dropping out of the scope's field of view


Being a bowhunter, I am fully accustomed to having a different aiming point for different ranges. Arrows have roughly the same initial velocity, but about 100 times the weight, so their velocity only drops about 60-70 fps or so out at 80 yards. It really isn't that difficult to "sight in." Basically shoot a group of bbs at each range, and note the mil dot associated with it. In time, the close shots would be done by feel, and the long shots could be done more accuartely.


Using the heaviest bb possible would be important. .43g would be the key(.88 too dangerous).


I wanted to do this at one time, but had no way of keeping the bb in the barrel without the hopup. Now that I use a sealed hopup chamber, the bb is held in place by the seal, so I could give this a try. I really like the idea of not having to mess with the stupid hopup anymore. I hate hopup but always assumed I was stuck with it.


I think that at 550-600 fps(.20), a .43 bb COULD reach 100 yards if the trajectory was correct. The question is just "can I aim that high and still see the target?"


I would sacrifice the 75-100 yard shots in a heartbeat if it meant "pinpoint" accuracy out to 75 yards. In this case, pinpoint is like what... 3" at 75 yards?

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The more I read all this, the more I think it's worth trying...


What would be the maximum Range a .40g BB would have with 500fps or 550fps (.20g)?

And how much would all this change in accuarcy?


And what is this system of the curved barrels you wrote about? That is new to me. Why weren't these systems so accurate?

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And what is this system of the curved barrels you wrote about? That is new to me. Why weren't these systems so accurate?


LRB's are old tech. I don't remember who came up with it first. Paintball through the Tippman StraightLine barrel or Classic Airsoft guns. They were not that easy to construct as the inside and top of the barrel caused the friction that imparted spin. It was hard to make that area consistent. Top that off with trying to keep the barrel smooth and without pressure fissures or bulges during the construction leads to a complicated construction procedure. While it would allow the bb's to travel far they would spread out pretty quickly. There are currently no companies that make LRB's that I know of right now. There are some people who can custom make them individually and there has been some talk about bringing them back into the mainstream. But that's about it at this time.


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Yesterday I put this idea of no hopup to the test.I haven't done enough testing, but my initial test determined that a 75 yard shot would be just about the extent of your range due to the bbs dropping out of the scope. I also learned that even .30bbs flew better without hopup than with hopup, and might be an option for this type of shooting.

I also discovered that my outer barrel was applying pressure on my inner barrel and causing it to curve left, which in turn caused my bbs to curve left. I wonder if causing the barrel to curve up by way of a custom barrel spacer might give you some hop. Of course if it turns out to be inconsistent, then I suppose a straight barrel would be better.

Now that I've solved my left hook issue, I'm probably going to be working more on my hopup system than experimenting with this no hopup concept, at least for a few weeks.


Let us know how it goes for you. It would be interesting to see what kind of accuracy you could achieve. Hopefully it's better than a hopup type system, but I've seen some hopup systems that work very well.

This video is not a gas gun, but the hopup system is what we're looking at here.

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