Quote Originally Posted by Shed tuner View Post
for a 28mm bore unless you have a v. small tp, I'd expect around 250-280g piston weight to be optimal.
If your port is at an angle (right angles) then this will obviously reduce flow, so I'd not bother testing with anything less than 3.2mm.

.22 will need less piston weight than .177 as you know
TP is a bit small at the moment (3mm). The reason being, a bit of bounce reduces the load on the gears and protects them a bit. The problem is that there are so many different pellets that I'm not sure how to settle on a TP and piston mass. If I optimise for popular pellets, there might be some odd outlier with super low start pressure that will end up damaging the gears.
Need to have a think about it.