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.

[FPoole]

Dang it, seems like just yesterday the top thing to do was to cut 3 mm off the comp. tube nut to shorten the port. Good thing I kept the original MarkI comp. tube. Now to figure out how to make it longer.

[cooper_dan]

Dang it, seems like just yesterday the top thing to do was to cut 3 mm off the comp. tube nut to shorten the port. Good thing I kept the original MarkI comp. tube. Now to figure out how to make it longer.

I think the top thing to do always has been, and always will be, buy more pellets and practice
Although saying that I have some brass tube on order to sleeve the TP down and start playing

Jim, I'll definitely take you up on that. Will probably see you some time in the new year

[NickG]

I have been experimenting with very short ports in the TX, at 21mm diameter tube the shorter you go the lighter you can go with the piston and keep away from dieseling.I have a 4mm long port which was great when I was at 98mm stroke , I now have the stroke much shorter but it now slams , it balances out in another tube i have with a 7mm long port , so now sleeving down the short one to see how that works .This springer lark is never ending

[bozz]

what about LGU tp size any more thoughts
Graham

[TonyL]

I don't own an LGU, nor have I had a play with one.

At one point, some owners were reporting drop off of velocity due to mainspring fatigue. Many attributed this to too small a TP, leading to excessive piston bounce, causing the spring fatigue. Not sure what the final outcome was, whether it was indeed this or just a poor batch of springs?

[Shed tuner]

I don't own an LGU, nor have I had a play with one.

At one point, some owners were reporting drop off of velocity due to mainspring fatigue. Many attributed this to too small a TP, leading to excessive piston bounce, causing the spring fatigue. Not sure what the final outcome was, whether it was indeed this or just a poor batch of springs?

Yeah, no change in that analysis.. port around 6mm long, needs to be around 3.2 minimum.

[bozz]

Yeah, no change in that analysis.. port around 6mm long, needs to be around 3.2 minimum.

Hi good that is what i have drilled mine out to, i was very surprised at the increase in power i had to compress a coil to get it back to 11 ft/lbs.
It just surprises my that you see a lot about Weihrauch or air arms but very little on walther tuning any idea why.
Graham

[Rickenbacker]

Because the Walther badged Umarex has only been around a few years, and it's not as good as the established HW or TX platform?

[TonyL]

Because the Walther badged Umarex has only been around a few years.......

Yes. Also the overall numbers of "high-end sporting springers" sold will be relatively low, so you'll have the Walthers competing for a slice of that market vs the more established (and trusted and known?) Weihrauch, Air Arms and Diana competition.

The prices of some of them won't have helped, either, plus the seemingly awkward parts availability. In the early days of the new LGV, it seemed to receive a bit of a slating over the finish and trigger function and variable quality (some shot beautifully whilst some twanged like the proverbial banjo on amphetamines). The "tuned from the box" image coupled to all these other factors won't encourage the aftermarket goodies suppliers to jump on that particular bandwagon.