So Jim, these long transfer ports as per your AGW article....

[Shed tuner]

I've long been suspicious that smaller ports shoot softer, due to cushioning the piston's landing / impact with the end of the chamber (at the end of the second, or in some cases 3rd fwd stroke, allowing for bounce).

http://www.airgunbbs.com/showthread....fter-shot-feel

But simply making a tiny port will mean it has too small a volume, too high a compression ratio, and too much bounce... also crazy small will choke flow too much.

So i'm wondering how soft your 3.4mm ported TX with 20mm long port shoots ?
I routinely reduce my TX ports to 3.5mm now, I much prefer it... but this is at std length ~10mm They will make a bit more power with a 3.7mm port, but not much. Shortening the port to 7.5x3.5 also works well. As in the thread above, LGV 2.6 x 25 is also a very soft shooting gun.

Also probably worth stating for awareness that this will have no real affect on accuracy, as it's all happening way after the pellet has left, but it does make the guns feel nicer, IMHO.

[BTDT]

I've long been suspicious that smaller ports shoot softer, due to cushioning the piston's landing / impact with the end of the chamber (at the end of the second, or in some cases 3rd fwd stroke, allowing for bounce).

http://www.airgunbbs.com/showthread....fter-shot-feel

But simply making a tiny port will mean it has too small a volume, too high a compression ratio, and too much bounce... also crazy small will choke flow too much.

So i'm wondering how soft your 3.4mm ported TX with 20mm long port shoots ?
I routinely reduce my TX ports to 3.5mm now, I much prefer it... but this is at std length ~10mm They will make a bit more power with a 3.7mm port, but not much. Shortening the port to 7.5x3.5 also works well. As in the thread above, LGV 2.6 x 25 is also a very soft shooting gun.

Also probably worth stating for awareness that this will have no real affect on accuracy, as it's all happening way after the pellet has left, but it does make the guns feel nicer, IMHO.

I think you may well be correct, Jon, but it's not an aspect I have specifically addressed yet.

I currently have a 3.3mm x 19.8mm port in the TX HC, and the piston landing velocity is 2M/s, while the 3.7mm x 19.8mm port full length TX has a landing velocity nearer 3M/s, though that could be influenced by the way the two rifles are set up (to give equivalent ME from the shorter barrel). I'll open the HC port and see the effect.

[cooper_dan]

Following this.

My TX200HC currently has the standard port. Wasn't sure whether to go:
- smaller diameter and same length. Possibly softer feel. (Good because I hold high up the peg without hamster)
- same diameter and shorter length. Increase efficiency and maybe remove a spring washer
- And now the option of longer length and smaller diameter

As it's my only HFT gun it will be left alone until the DMHS is over. But interested to see what you find.

[Shed tuner]

Dan, just sleave it down and try it... easy to do, and even easier to reverse if you don't like it. Shortening is much harder from both persepctives...


Jim, 2 vs 3m/s sounds like a noticable difference.. let us know what happens when you delve deeper

[BTDT]

Jon. I've been reviewing existing shot data from various TP lengths and diameters, and it points to any direct effect of either length or diameter on piston landing velocity being dwarfed by the consequence of their effect on piston bounce.

It's a springer, and everything is affected by everything else.

Dan. Next time you're coming to Nomads, let me know and I'll bring the HC with 3.4mm x 20mm port for you to try.

[TonyL]

Yet again, a most excellent and informative article, Jim.

And a most ingenious and flexible way of playing with both the stroke and TP dimensions.