Tanio Koba twist barrel - fps versus energy
 

Hi,

Knowing that TK Twist barrel work best at 330 fps, I was wandering about the following:

IE TK twist barrel is a function of velocity, not energy?

Let say you have a AEG running 350 fps with 0.2,

So, around 320 fps wit 0.25, would this be the sweet zone as well (the 330 fps)?

I would assume it pure velocity not energy, but I m curious if someone knows...

The TK Twist is a function of ENERGY. That is to say, the Tanio Koba Twist barrel is designed to work with 1 Joule OR LESS.

In my threads regarding this barrel, I did mention 330fps, but only because that is the energy equivalent conversion for a 0.20g BB. I did this because it is generally easier to understand by many users, but at the same time, I saw that it caused confusion as well, as users stated "well, then I can just use 0.30g BBs with my 400fps gun to bring it down to 330fps." It does NOT work that way. 1.4J is 1.4J, no matter what BB wait you put in there.

1 JOULE OR LESS!

My understanding is airflow, or speed at which the BB is travelling through the barrel, is the critical element for the TK twist barrels. As long as it's a 6mm ball going 330fps or slower going through the barrel, BB weight shouldn't matter at all.

That understanding is incorrect. A heavier projectile may travel slower out of the muzzle, but the air that cyclones out of the barrel will still be faster than 1 JOULE OR LESS.

That understanding is incorrect. A heavier projectile may travel slower out of the muzzle, but the air that cyclones out of the barrel will still be stronger than 1 JOULE OR LESS.

The effect of the barrel is dependent on the air flow, so it is the ENERGY is what must be controlled.

Ah, good point, you are correct.

I have a twist barrel in both a pistol and my P90. One thing we found is that with an upgraded gearbox shooting around 400fps the barrel had less accruacy and distance then a stnadard tightbore.

Running stock or slightly upgrade 333fps gearbox, I found the grouping to be much tighter and the range equal to if not greater then my standard barrel.

In my pistol shooting approximately 390fps, I found it nearly doubled the effective range of the pistol and tightened the grouping of the shots by to about a 3" spread at 60'


*EDIT*
I should also make note, that for some reason on my P90 several different chrono's cannot read fps from the gun, so it might be a good idea to carry a stock barrel with you to show that your guns gearbox is within field limits if required. I've seen 4 differnt chronos out here now that cant read the fps or it it does it says 50fps with the twist barrel, and 320 with the stock one. Tried white, black even green, and glow in the dark bb's to see if it made a difference to the chrono with no change.

For the sake of my curiosity, I have a AEG with easy spring swap, I ll do a quick test this week, basically running a TK twist:

Spring rated at 400 fps with 0.2 (0.2 and 0.25)
Spring rated at 330 fps with 0.2 (0.2 and 0.25)

I ll share my result

I have a question about those twist barrels as well, figured this would be a good place to post it. Would putting a twist barrel into a pistol yield better results than a standard TB?

yes it would, because these barrels are rated to about 1.1 J

Figured that, thanks Boar.

Not true it depends completely on the pistol my WA doesn't shoot close to 330, pistol or AEG your gun should shot 330 with .20 for the twist barrel to be effective.

Yes, I know that. My Hicapa will shoot around that I believe, so I think it will be very effective.

I run a short TK Twist barrel in my P90 @ 1.7j i do not notice a relevant measurable difference in groupings at 100ft+ over a Prometheus Tight bore of the same length.

At 1j energy the TK barrel is slightly better than the Prometheus tightbore of same length in groupings <100ft.

Sorry I should have mentions the twist barrel in my P90 is m16 length, as well as my standard barrel. I threw out the stock short barrel years ago lol.

Illusion's already done extensive testing on the matter (so you don't have to), just take his word for it. Really, he DOES know what he's talking about lol

So what's the consensus on this?

A TK Twist barrel on something like a Hi-Capa 5.1 should double effective range and give you tighter groupings (as it shoots at about 1J)?

I'm actually considering running a pistol as a "forward scout/recon" but I have to do a lot of research and info gathering before figuring out the setup I'm going to use and equipment that I need to buy.

From what I can make of it the tk twist barrel is simply a balanced system in which you you bleed hi pressure air around the BB. So the BB is basicly surfing the inside of an annular wave...

For this to work you have to factor in acceleration within the barrel lenght 0 to 300 fps.

Your first constant to control acceleration will be BB mass
So constant BB size and constant will be BB weight are essential...

Because lo weight BB = quick acceleration not enought pressure bleeding to create
the hi pressure buffer you need.

High weight BB = to slow acceleration to much bleeding PROBABLY turbulence and restriction upstream

Now that you have control over the mass you must accelerate you work on the bleeding with the crestes (or grooves) in the barrel. Same problem has with the BB weight.

To big to much bleed, to small not enought bleed to create buffer

The twist (again balanced according to speed/acceleration) in the barrel keeps the air from the high pressure wave plastered again the walls to restrain its effect (turbulence etc) on the BB.

So from knowing this I would have to guest that someowe... I japan 300 fps must be somewhat popular...

or that they could not manage tuning at higher FPS

((this is over simplied has there must be a lost to consider in actual overall barrel size to allow optimal lateral movement within the vortex..))

Regards,

Pete

So yes... only works with .20 BB and 330 FPS must be a Maximum... faster then that precision degradation must be.... horrible

I say put a TK twist on it if you play indoor or where there is no wind or bushes. With 330fps I had trouble shooting through small bushes with very little density, that and I could see the winds take the bb (especially .2) and now play between 360-370 fps. Honest though I feel a need for more range as some hot guns that are shorter barrel length outrange me.

I just ordered a Systema M100 Spring to put with a 509mm TK Twist into my M16, I was told about 350 Fps Maximum and according to 2004 spring chart, this would pull 360 new, so decreasing would have got me "in the zone". I'll make outdoor test once I get the chance to measure precisely while putting 280 FPS on .25 and after that with the new spring, to compare the grouping at equal distance and conditions.

Heavier BBs will fix those issues for you, minimum 0.25g, but 0.28g are better.

You'll notice that the spring chart was done with an P90 (chosen for it's well sealing hop up unit) and there are also upgraded (for sealing and efficiency) parts in there, so the chart isn't 'perfect', even though it's well done. But ya, Modify 100 springs tend to sit guns around 360fps as well.

Then it might just suit in as well, it is rated 365 on the chart, I've heard that max FPS with a TK twist was around 350, now there's proof that it suits best under 330, so I think I'll be in the optimum zone while I might have little air leaks, but I tried different nozzles and this one doesn't leak. Can't wait to see if I can reach a sniper-like grouping :)