Tx200 zero transfer port

[wonky donky]

well I will just machine up some breech seals as they will be the part that does the port reduction size and see what works and hat does not...im thinking 3mm to start and push up from there if the velocity lowers to much...i do know 4mm is to large already

I did all this with my short stroked (68mm) 25mm HW77 & sent you all the results last year some months prior to the springer bash if you think back, I have something like 30 A4 pages listing port sizes/spring dimensions/velocities/different pellet brands etc. I tested various screw in port lenghths sealed, unsealed, protruding into the barrel, away from the piston head, directly on the seal.

I even tried different recess widths & depths on the piston head to create lost volume. The recess was placed directly behind the transfer port & a 10thou recess gave added velocity, cant remember the details off hand.

I did exactly the same thing with my HW80. tedious job I can tell you!

Are you able to make your TPs with a tapered bore, so the air enters at the small end (which should be radiused) and then expands as it leaves the TP?

Mike's point that the expansion brings about the cooling and the increased weight of air behind the pellet is for me the clue.

Also, the whole system needs some resistance to flow to work against, otherwise if it is all down to pellet tightness in the breech, the shot to shot consistency must suffer. A TP that absorbs some work is a constant that buffers those variations in fit.

In the world of PCPs, which may be a sin to mention (!), one of the most consistent rifles ever made was the Pro-Target, and if you look at the air path it is positively tortuous and not conducive to efficiency. It means however that the pellet fit in the breech is not all that relevant. At the other extreme we have the Stealth with its straight through concept, and it's no secret they can be devils to set up and keep stable.

Tapered port; I did this on my Webley .177 Tomahawk many years ago. I'm about to revisit it using the TX as I have four compression plug blanks left over.

Your right about shot to shot consistency without a port, it's not as bad as you may think, I've not had chance to accuracy tests yet but I'm pretty sure the TX won't be hold sensitive however I think it will produce fliers.

As for the Pro Target mine is no better than my EV2 & neither not as good as my HW100 consistently wise, all accurate with the right pellets though. the stealth is another story & I think your being rather kind there!