Tx200 zero transfer port

[Shed tuner]

Yeah, zephyr grooves, but you need a port (i got a few fps extra when I tried this, but not a lot)...

Mote is a 2mm thick 25mm OD washer stuck in the end of the comp tube, with a nicely radiused port, 4mm should be fine. Radius can be quite wide/deep as the port vol is so low.. would only be around 0.5mm of parallel sided port in there (after the entry porting).

[bigtoe01]

quick drawing, no detail on taper as i have no time to measure a spot drill (which i still feel will be best...a small one )

https://dl.dropboxusercontent.com/u/920660/wonky2.png

[Rich]

Ideally the entry should be a radius rather than a chamfer, if you can manage it. Maybe be easier done by hand?

[Shed tuner]

Would the exit side 5mm not be better off staying at or below the calibre ? Otherwise the diverged air is going to hit into the breech face ?

[Snooper601]

Would the exit side 5mm not be better off staying at or below the calibre ? Otherwise the diverged air is going to hit into the breech face ?

Port matching like is done when porting an inlet port on an engine. I managed a very useful gain by removing the square edged step on a Fiat twin cam 2l engine where the inlet port in the head met the inlet manifold, it made enough extra power to increase the top speed on the Autobhan by 25mph and that was nearly 25 years ago.

Cheers

John

[bigtoe01]

Would the exit side 5mm not be better off staying at or below the calibre ? Otherwise the diverged air is going to hit into the breech face ?

the entry is 5mm, the exit will be a lot less...i should have labelled the drawing a little better.

5mm to 3.6mm taper, then 1mm at 3.6mm, then 3.6 to say 4.2 on the exit side

entry side radius cut, polished....im thinking it will work well

[Shed tuner]

Ahh sorry, yeah, makes more sense that way lol... in my mind they always flow R > L
Are you left handed ?

[Artfull-Bodger]

Guys you can use a radiused center bit (as opposed to the 60deg type) for the inlet into the port, they come in many sizes, surely you can find something close to what you want?

[TonyL]

Mote is a 2mm thick 25mm OD washer stuck in the end of the comp tube, with a nicely radiused port, 4mm should be fine. Radius can be quite wide/deep as the port vol is so low.. would only be around 0.5mm of parallel sided port in there (after the entry porting).

Yep, that would get my vote.

[TonyL]

Guys, maybe not the right place, and maybe a curveball,

But.......Are there any situations where a LONGER transfer port can actually be beneficial? I accept that shorter ports indeed seem to result in higher efficiency, but would it be possible, for certain applications, that a longer port could improve the shot cycle and resultant smoothness, reduced recoil /surge??