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Tanaka Guide: How To Upgrade The Tanaka M700 A.I.c.s. Hop Up System

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Alright, This is a repost of the guide that's been posted before with credit to me. The actual author of this tutorial is Z06C5R from the AirsoftRetreat.com forums.


This Guide is very well done, I have used it to great avail without even having to ask the original author any questions about how to complete the upgrades


I have additionally included the follow up conversation with Z06C5R which consists of only 2-3 messages.


All pictures have been uploaded to photobucket




First message to Z06C5R ––


Hey man,

Ive been reading your posts, and I share the same sentiments about the unreliability of the hopup and barrel. So as soon as I get enough information to make a wise decision on hopup shape, I will be buying a barrel from DEE's customs. I think I ruined mine when I shot old old old air gun pellets through it. They went straight down, but They still shot and dented a thick piece of wood. hahaha, that was a pretty freakin bad choice, but oh well, I guess I was planning on getting a new barrel eventually for increased accuracy.


SO Im asking for an instruction set on how to stabilize the existing hopup. Also what is it's shape so I can order a barrel soon? Dees can make either square or circle hopup cuts in the barrel.



Thanks ahead of time and for turning me away from the BGS kit. Your advice has helped me a lot.





Reply Message ––


If you are keeping the stock hop (which is what it sounds like to me) you want the SQUARE cutout.


As far as some instruction on stability mods go... I could try to explain it here, but it would probably come out pretty messed up and not make much sense. How about this instead: I'll pull apart my gun sometime in the next few days and take some pics of what I've done, and explain how to do them. That should be a bit easier to follow.



Actual Guide, thanks Z06!!! ––


Before we begin, here is some hopup theory: In my experience, there are 2 factors that affect the consistency of a hopup unit: Shape (of the part that contacts the BB, not the unit as a whole) and stability. As I've mentioned, the AICS bucking as an awesom shape in terms of putting a consistent spin on the BB. Where it lacks is in the stability department. All the great stuff you've heard about the best gun hopup bucking? It's ALL stability. The BGS bucking has the SIMPLEST shape ever conceived for hopup bucking - I've pulled more complex units out of a $40 spring pistol. What makes is good is the fact that it's solid as a rock from shot to shot. It's not some magic super complex V-groove bucking that imparts perfect spin each time, not by a long shot. People see an improvement because it's WAY more stable than the stock one, pure and simple. So, what you've got is the BGS hop that's rock solid but poorly shaped, and the stock piece that's shaped perfectly but unsteady. If you take the stability from the BGS unit and apply it to the stocker, you've got the recipe for one kick-:censored2: hopup setup.


You'll need:

The wrenches that came with the gun

A philips screwdriver

Some electrical tape

A good eye


I recommend:

A drill press

13/32 drill bit

Teflon tape


Begin by removing the receiver and barrel assembly from the stock as detailed in the manual. The outer barrel slips right off to expose the inner barrel. You'll notice down where the barrel goes into the receiver, it passes through a large brass nut. Wiggle the barrel a bit, and you'll notice it's kinda loose inside that nut. That's one problem we'll solve later. For now, you'll want to unscrew that nut and remove it. Now push out the two pins I'm pointing to below. Make sure your bolt is open, and wrangle that barrel / hopup assembly out of the receiver - it slides right out the bottom.



Next, you'll have to remove the little C-clip in front of the black plastic housing. I'm pointing to

it below. If you've been paying close attention, you'll already know what that tape in front of my housing is for, but that comes LATER because it interferes with disassembly.




With the clip removed, you can slide the outer housing down the barrel and remove it, leaving you with the inner housing and the barrel.




Take the wee little allen wrench that comes with the gun and loosen the little grub screw atop the housing, it doesn't need to come out, just loosen it. Pull that sucker off to reveal the guts of the hop - then take them all out. You'll wind up with this:




Ok, the first problem is that brass collar. It tends to rotate side to side on the barrel, and it drags the bucking piece with it. You want to put a VERY slight bend on it so it's not perfectly round, and thus fits much tighter over the barrel - picture fitting an oval over a slightly wider circle. Slap that back on the gun and set your bucking back in it. BEWARE: Mine is in backwards. The notch in yours should face forward. You'll notice the U shape in the bucking is tapered - you want the wider end facing the back of the barrel, which *should* mean that the notch on top faces forward.




Now comes the tricky part. We're going to wrap the assembly pictured above in tape to hold everything in solidly. It sounds simple, but it's crucial that you tape it just right so the bucking is held in correctly - a wee bit of extra pressure on one side or the other will cause the bucking to lean and send your shots flying in an undesired direction. And that's not the only problem: The housing as it is will not accommodate the slightest bit of tape in there, not even Teflon tape. Now, my housing was bored out to 13/32 to fit the BGS bucking, and I find it JUST fits one wrap of electrical tape. However, drilling out the housing MUST be done on a drill press. You may be able to get away with a wrap or two of Teflon tape if you file the housing out a bit, but I haven't tried it. Let me know which way you want to go, and I'll give you more info. Also, here's a hint for wrapping the bucking correctly: Look down the barrel as you wrap it and make sure the bucking protrudes into the barrel equally on each side. In other words, make it level. You can adjust it by stretching the tape and otherwise playing with the tension on either side of the bucking. (This is why electrical tape is good for this stuff). Here's the taped unit:




Once that is set, you can slip the housing back onto the barrel. You'll most likely have to sight down the barrel again to get the top of the housing lined up with the nub protruding into the barrel, since you want the actuator to be contacting the center of the bucking. Tighten the set screw down again, and you're good to go. Before you slide the plastic outer housing back into place. you need to place a few small pieces of tape on the top of the inner housing where it slots into the outer housing to prevent it from rocking side-to-side. Don't put so much that it won't slide all the way forward, and don't put any on the front of it. Just on the sides, or else it won't line up with the top of the actuator. It should look like this when done:




With the plastic outer housing back in place, replace the C-clip. At this point, you have stabilized the bucking and the housing. Now, you need to do the barrel. Remember the tape under the brass nut earlier? Yep, it's time for that. You'll remember the barrel has some play within the opening in the nut - you must eliminate this. Wrap the barrel several times where the nut goes, so you are essentially filling that gap with tape. It ends up looking like this:




Now that everything is held firmly in place, you need to check your alignments. Before these mods, the barrel had a good deal of free-play that allowed it to move a bit to fit into the outer barrel. Now, that has been eliminated. If you try to fit it without checking alignments, you'll more than likely be putting a warp in the barrel. Checking alignment is simple: pull out the plug in the end of the barrel, which will leave you with a hollow tube. Put everything back together as normal, leaving the plug out, and tighten it all down. Put your rifle on a stand, or rest it on the bi-pod or whatever, and look down the barrel. Chances are, you will see this:




Fun, huh? That plug would have forced the barrel up about 1/2 inch. Not good for accurate shooting, LOL. The fix is pretty simple. All I had to do is turn the front screw on the receiver out a bit, which raised the inner barrel inside the outer barrel. (The outer barrel is held separately from the receiver and inner barrel, so moving the receiver moves the inner barrel without moving the outer barrel) Kinda hard to explain, but it works amazingly well. Your goal is to get it to look like this:




I made a mark on my receiver to let me know how far to screw it down for future reference. Now, all I have to do is tighten it until it reaches the line, instead of re-aligning it every time. If your barrel rests in the top or to the side of the outer barrel, let me know, because those will be a bit harder to fix. Here's that mark:


The picture that goes here is in the following post due to image limits on this forum


Replace the plug, dial in the hopup again, and start shooting!

In writing this, I probably overlooked many things that have just become second nature to me by this point (I've taken this thing apart more times that I can count). Some of the stuff in here is pretty straight forward, but things like wrapping the hop take some getting used to. You'll more than likely have to go in many times and tweak with it, and you will begin develop a fell for how to get it right. I'll try my best to help you figure out whatever binds you get into while you're learning, so feel free to shoot me as many PM's as you need to to get this sorted out.

Good luck, and let me know how it turns out! I'd love to know what my rifle COULD have shot like if I knew all this stuff from day 1, but somebody has to do the research, right?


No problem man.


As far as accuracy goes, I really coulden't tell you. My gun seems to have a mind of it's own. I'll go in and spend hours tweaking with it, and it may yeild a slight improvement. So I chalk it up as a sucess and put the gun away. I'll then take it out the very next day, and withiut having so much as breathed on it, it will immediatly shoot terribly again. The barrel alignment is a perfect example: I just figured that one out last week, and once I got it all lined up, the gun was shooting great (great being a releitive term). I put it away and a few days later pulled it out to do some target shooting. At 100ft, I couldent hit am 8" wide box for my life, while just days before I could hit a 12" wide tree at 150ft every time. It always seems to go like that - Does fine when I'm just plinking, but when I actually want to sit down and really go for it, it sucks. Keep in mind I'm using a less-than-perfect bucking peice, however, and that's contributing to it a lot.


I'd say good call on waiting on the barrel to finish the mods, since you mentioned yours might be screwed up. That could throw off your results bigtime...


So thats the skinny on how to upgrade your M700 AICS, and to great success too, I've definitely decreased grouping sizes and in-field accuracy with these mods, but unfortunately I have not had a chance to airsoft at all here in college, soon I hope to be able to and then I will post my findings on how successful these mods are after having the gun sit for a while.


All these modifications performed on pre-ban guns, I disclaim responsibility for any damage you do to your own gun





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