Tanio Koba TWIST Inner Barrels.

[MadMax]

Maybe, nobody really knows how airsoft barrels work. I suggest that Illusion dyes the inside of his barrels with permanent marker ink and fires off a bunch of rounds. Sacrifice the barrels by cutting them in half to examine where the ink has scuffed of on bbs. Saving that, maybe someone with a rifle borescope can help out with this discussion and save us from having to cut barrels apart.

Apart from making observations of shooting performance from range tests, it's pretty difficult to really say how bbs touch the inside of barrels without direct observation.

[gandar]

Sorry, what I meant by that was that a tightbore doesn't hug the BB on all sides, (the concept of rifling that Drach is stuck on) I know they bounce around, hence the benefit of the Twist barrels (keeping it floated in the centre of the barrel). What I was getting at, was that a tighter bore would have less space around the BB for the air to pass by, thus allowing a higher velocity/power with the Twist barrel.

[ILLusion]

I see.

The twist inner barrels pretty much forego that idea... After all, what's the point of having a BB go 5fps faster if it's more inaccurate than when it was 5fps slower?

[gandar]

....I realize that.

The Twist barrels increase shot consistancy. They only work up to about 330fps.

Assumedly a gun shooting hotter is going to shoot farther (albiet, at this time it loses consistancy at that range).

The reason (if I'm reading it right) that a Twist barrel only works to 330fps, is because the air starts going past the BB and screws with what the barrel is trying to achieve in the first place.

Therefore, if you were to tighten the bore of a Twist barrel, you have less air escaping around the BB. This, in theory, would allow a higher velocity (because the air wouldn't be escaping around the BB) and not be detrimental to the effect of the Twist barrel. That way you get the increased range of a higher velocity gun, but at the same time, you get the increased accuracy of the Twist barrel.

(Sorry, I had a horrible sleep last night, so I'm having trouble expressing what I'm trying to say... Brain no workey)

[ILLusion]

Okay, I understand what you're trying to say now.

I don't believe the high power failure is because the air starts to go past the BB. I believe it's because the rifling grooves are only optimized for a certain power rating. If the twist was stretched out or tightened up (I'm not too sure on the physics behind rifling), then it may be better optimized for high powered guns.

Japan has rules that restrict guns from shooting beyond a certain power rating, which is why Tanio Kobayashi skipped the idea of optimizing for higher power.

In fact, just last night, the manager of the First Factory store in Japan, along with five others in the shop were arrested for illegally owning and modifying airsoft guns to limits which could "cause harm or death."

[gandar]

Originally Posted by ILLusion

Okay, I understand what you're trying to say now.

I don't believe the high power failure is because the air starts to go past the BB. I believe it's because the rifling grooves are only optimized for a certain power rating. If the twist was stretched out or tightened up (I'm not too sure on the physics behind rifling), then it may be better optimized for high powered guns.

Slowly but surely, my brain is turning on.... Anyway, I think you *may* have mentioned that before. It does make sense that it would work that way (try pushing something loose over a spiraled column of some sort, if you push it slowly, it'll follow the grooves, but if you push it quickly it skips over them), however I'd be curious to know how difficult it would be to spin those grooves down a barrel, and if it would be feasible/possible to try recreating them at a more optimized ratio, be it shorter or longer. I would guess that the twist would have to be stretched more, and I'm sure there's a point where it would cease to be effective, but if it's reasonably possible to "rifle" a standard, or tightbore barrel with similar grooves on a different scale, it would be interesting to see the results.

Maybe MadMax the machine shop guru could shed some light on the difficulties involved in doing something like that...

[MadMax]

I think the TK grooving would either be swaged or broached.

Swaging would involve pulling a tool down the barrel which deforms the material to form the shape. The tool would have helixed lobes and would be rotated as it'd drawn down the barrel.

Broaching uses a progression of cutting edges to shave the profile. The forwardmost (first) cutter removes say only 0.002" of metal and the one behind takes another thin chip. A progression of 5 cutting edges could remove 0.01" of metal per pull which sounds about how much a TK barrel needs. After broaching, a polishing stage would be required to take off the burrs and clean up the cut surfaces. I wouldn't be surprised if polishing could be accomplished by pumping an abrasive paste thru the barrel for awhile.

If TK was uber advanced, they could be using an electrical discharge technique which ablates metal with electrical discharges. I kind of doubt that they're doing that though. It's an expensive slow process which is usually used for hard steels. I think Glock barrels are electrically ablated to form the rifling. With electrical ablation, you can do crazy stuff like progressive rifling which varies the helix angle from beginning to end. Start with a gentle helix and end with a steeper one so you apply a more constant torque on the bullet as it accelerates down the barrel. SVI does that I think.

[gandar]

Very cool. I've used broaching to form splines on the inside of a hole before, so I'm aware of that technique, and I would be inclined to agree, for the depth of the groove, you could probably just deburr it with some sort of abrasive paste/liquid. Is it feasible/easy to do on a consistant, helical path down an entire AEG barrel?

[MadMax]

Originally Posted by gandar

Very cool. I've used broaching to form splines on the inside of a hole before, so I'm aware of that technique, and I would be inclined to agree, for the depth of the groove, you could probably just deburr it with some sort of abrasive paste/liquid. Is it feasible/easy to do on a consistant, helical path down an entire AEG barrel?

I have no idea as I have little direct experience in the techniques. I would think that a viscous paste would tend to follow the grooves. Even if it didn't, it'd wear off burrs.

[NOOB]

Can we somehow distube this article/test to other friendly forum for discussion ? Knowing that it had been debate to death, still this is a great article and it's good to share with the entile airsoft community.

[ILLusion]

Feel free to forward the link of this thread to other discussions on this topic to other forums.

Google will soon pick up the contents of this article. The more this article gets linked, the higher it will rank.

[Gryphon]

Originally Posted by MadMax

With electrical ablation, you can do crazy stuff like progressive rifling which varies the helix angle from beginning to end. Start with a gentle helix and end with a steeper one so you apply a more constant torque on the bullet as it accelerates down the barrel. SVI does that I think.

That's known as gain rifling. The M61 Vulcan cannon barrels use this (among others I imagine) to minimize the initial rotational torque on the projectile.

[MadMax]

Originally Posted by Gryphon

That's known as gain rifling. The M61 Vulcan cannon barrels use this (among others I imagine) to minimize the initial rotational torque on the projectile.

I think the point of constant rifling is to exert a constant torque.

A rifling with constant lead requires the bullet to spin up to whatever rotational rate which corresponds to the instantaneous forward velocity. I'm guessing that a bullets acceleration may be higher at the root of the barrel so you'd be exerting a higher torque at the beginning of it's travel than at the end. I think gain rifling matches the bullets accelleration at each point in the barrel with a constant corresponding rate of rotational increase which requires a constant torque.

I conjecture that this reduces friction in the rifling (barrel heating) and perhaps wear on the barrel and bullet.

[Kurgan]

So... Where can I get one for a TM M16A2?

[Ambor]

Originally Posted by ILLusion

I'll have to let you know how range compares in a 1J Twist setup versus a high powered tightbore setup.

When do you guess you will be doing some tests? The groupping info would be much appreciated, as really the use in guns over 330fps is quite an interesting topic.