What @Steve 1974 said. The only reason I tried was because I had pretty clear cut bounce and I went very slowly testing in between sizing and only going up a fraction or two mm at a time. All in I ended up with a 20% bigger transfer port and a 15% lighter piston. All said and done it was about 3hrs worth of work.
I do like the idea of interchangeable inserts. Seems interesting none of the major high manufacturer's offer something like this. Rifles like the tx200 which are marketed as FT capable you might think would have a thread port. With the option to buy tuning kits that have an assortment similar to motorcycle carburetor jet kits.
I'd use grub screws with the centers drilled out to various sizes. Then you can use an allen key to swap them easily
I'd be very careful with that. I know from building race engines that airflow at high velocity is very easily disturbed by the least changes in area and shape. Your methodology is firm from a servicing aspect. But the shortened port length and inside corners on a grub screw could totally alter airflow. The socket head will create additional lost volume as well. They'll be some sort of step where the grub screw meets the compression tube. At the velocities the air travels through the TP even drilling scars can alter airflow negatively.
Good to know! The other option, and probably the one I'm going with on the TX, is drilling out the TP and sleeving it if needed. I actually have an idea for an easy to make ultra light piston that I'm going to start with. Then I'll deal with the spring and TP in that order.
A shoelace covered in autosol metal polish works a treat on air rifle ports , thread it through and work back and forth
Down to cost , good design the tx but they not well finished inside , nothing fits properly. And the prosport is naff, it’s pretty though
You could convert the tx to a 22mm setup
