I have posted similar informations in two other threads, but I will replenish the informations even here, because this threads looks be more concrete and more helpfull for others nelson tunners:
Inspired by the modified WGP Ranger Powertube mentioned in first post in this thread I have performed similar test with my tunned Kingmann New Hammer PT (more about the tunning in Kingmann New Hammer SC efficiency tunning report
thread). In my case the max. velocity raised from 260 fps to 288 fps... but the efficiency has been reduced (= bigger gas consuption for given velocity) - imho because the dwell was not optimal for the new enthanced flow (more gas wasted by entire operation of the valve with bigger flow). The exact effect on my New Hammer on powerlets was such like (blue = before):
After dwell reduction (stronger valve spring and further hammer lightening) even the generall efficiency has been enthanced:
But along my experiences for the best results even the another parts what are connected with the PT needs be modified: the valve seat (= valve nut) and cup seal - there can be the flow likewise enthanced. Imho the optimal shape of the cup seal and the valve nut is such like:
The final effect on my marker was:
So thank you for the inspiration. The mentioned PT mods are is surely steps on in the right way.
Up to now I have not performed polishing of the PT ID surface or entlarging of the ID. I belive that they work, but I have a little fear from them up to now.
...but it looks so that PTs even with rough and small ID (4,0mm / .157") are not the worst limitation - you can get (imho) great results with them, when are the other parts of the marker perfected.