Tx200 zero transfer port

[Shed tuner]

I think a couple of truths emerge from this. We do need a transfer port to provide the choke. Within sensible limits, the diameter of the port is more important than its length, although a minimum length is required to establish choking: the shorter the stroke, the smaller is the transfer port diameter required for maximum energy efficiency.

Mike

Hi Prof Mike,

So for the choke to function as such, presumably the port only needs to be smaller than the rifles calibre ? So 5mm could work on a .22, but no good on a .177 ?

Subject to it causing enough air acceleration to reach the required velocities / actually choking the airflow.

Thus if WD were to install a 1mm thick washer at the end of his comp tube, with say a 4mm port, that should provide adequate choking, whilst keeping the very low lost volume ?

You reference a minimum length to provide choking - is this just a case of being long enough to get some kind of "organised", or close to linear, airflow through the port ? Any feeling for what this length is - we know empirically that 4mm seems to work well (Tony's D52), but would say 1mm or 2mm be enough to get the required flow characteristics ?

Sorry for all the questions - but this (flow/choke) is an area we've not gotten into yet !

Rgds - JB