Lets talk about transfer ports…
I have noticed that Crickets (and probably other guns as well) seem to have different size transfer ports. The cricket has 3 TP’s as far as I am aware of. One in the barrel, one in the breech block and one in the valve. How come they are not the same size? Would it not be optimal for performance if the were equally sized?
Just as an example we will take a look at Octavius .22 Cricket.
Valve: 4,35mm
Barrel: 4,02mm
Breech: 5,06mm
Surely it would be better if the were equal? Say just as an example 4,5mm, like this:
Valve: 4,5mm
Barrel: 4,5mm
Breech: 4,5mm
Does anyone have something to say about this?
All Replies
The transfer port of the valve and the breech being different sizes may have to do with tolerances and assembly. If they are the same size and don’t get lined up, perfectly centered, the area of the air flow will be reduced(Try lining up two same size tubes slightly off). Ports that are near the same size may run the risk of being off center and restricting the flow.
As far as I know the transfer port should be different for each caliber. A 50 fpe gun obviously needs a bigger transfer port. A big transfer port on a sub 20 fpe would be very inefficient. That’s why they match the transfer port to the different Cal. I know the Evanix guns shot very hot and have large transfer ports. You can’t get any decent shot count out of them even if you choose to detune them. In all fairness their valves have big ports too. So that contributes too. That’s why to get cricket to go beyond factory power you need to increase the tp to get more air behind pellet.
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Thanks Cricket, makes it much clearer now.
I think, with all three different diameters of transfer ports, the smallest diameter is ultimately the determining dimension as far as air flow is concerned. It is like a multi lane road. The one with the fewest lanes will constrict the flow of traffic, just the same as air flow.
As to why the Kalibr has different diameters is beyond me. Each reduction in transfer port diameter along the way is the same as “attentuation” if it were a flow of signal in a wire. A speed bump shall we say.
I am wondering if we could also know and compare the transfer port diameters of the Vulcan, Taipan, Edgun, and other high end bullpups out there. That would be an interesting comparison.
Thank you for sharing the photos, that was mighty fast.
Ok, this is how it looks like in a Cricket, the white indicates where the tp’s are. In the breech it is like a “pipe” that aligns with the barrel and valve tp. (If you can’t see the whole picture then click it and it will take you to the album)
Breech block:
Barrel:
Valve:
I hope it makes more sense now
I think that you might be right because the guys with M-rods are matching the transfer port and barrel port sizes for more power. Maybe the trade of is less efficiency so that might not be optimal for everyone.
I’ll get on that, you’ll have something within the hour
It would be nice if you have a sketch or drawing showing the arrangement of these three different transfer ports of different diameters happen in a Cricket. Thanks.
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I don’t like the fact that the air has a nice big passage all the way until it hits the barrel where all of a sudden the hole is a lot smaller wich creates that “speed bump” that sounds inefficient to me.
A very good idea to compare with different brands, lets hope some people with edguns, taipans and vulcans etc join in.
Thanks for your answers and HAPPY HOLIDAYS!