I recently found out about the TK Twist barrels and it really interested me. I was wondering if you elongated the rifling and thinned out the groove if it would be usable with a higher FPS setup then 330. Just a thought.
They need to machine a barrel that can still put that pocket of air around the bb at a higher velocity. If they could do that for having a 430 FPS cap, it would be gold. Then again, maybe they tried and it didn't work :/
The longer the TK inner barrel is, the higher the FPS you can use it with is. The longest one they make (509mm) has be used successfully up to 380 FPS. After that, you begin to lose the special performance that the TK offers.
The air escapes around the bb instead of staying around it and providing that cushion. However, the barrels work better the higher cylinder volume you have. In a BASR, it can be used at a slightly higher fps than an AEG, wherein a 509 can be used in the a&k sr-25, because of a larger cylinder,at about 420 fps.
The reason why everyone is always saying the 350 fps is due to Japan law. But nobody will ever put one in a 500+ rifle and test it out. All of the "experts" are always people who heard it from another person who saw it, or read it from someone else. There is NEVER any first hand experience.
You now what. I'm going to buy one and put up a review. I have a decompressed spring that shoots around 320, give or take, and a laylax spring that should give me 420 FPS. If it fails miserably, then I'm out $80 :/ I might even get ASGI's PE spring if I'm felling crazy.
I was just checking out the TK barrels as well and they seemed very interesting. Sadly $80 down the drain isn't something that I have much of a choice in doing. So Toast, you are the MAN for being the guinea pig. I cant wait to hear your results.
Actually, I do have first hand experience. My spotter's SR-25 was acting up, and we had about 2 days until game day. His rifle shoots at about 460 fps. We stuck the TK barrel in it, with a firefly bucking, and now have a beautiful flight path out to about 230-250 feet. I would take a video, but he just left for Calgarie, so I won't see him ever again to take a video.
Anyway, it does work at higher fps, but you have to have a big cylinder, because the volume of air will make it so that the cushion of air is still there. That is why it worked with the SR-25, it has a PSG-1 cylinder, so the cylinder volume is big enough that it works.