I have no means to measure the pressure, however it has been modelled (via computer) and it shows no issues with the RWS pellets etc.
It has to be the odd ball batch had slacker/smaller dia skirts, the gun must have been suffering blow by, however the shot cycle is so fast now its hard to tell when im chrono shooting here as the gun is not in the natural shooting position. However with the RWS 4.51 the shot cycle is fast but soft and velocity very consistent.
If I get a chance this week i will make up that pellet seater, the transfer port on this TX is 3mm shorter than a stock one so I can afford to add 1mm back on and should not see much difference, I will test with the RWS and the newer 2015 batch and see what comes out.Some of the old HW55's used to like the pellets being seated a couple of mm down the barrel so you just never know.
Something else I thought i may make up is a machined brass bar that just is a slide fit into the barrel on the TX, then see if it will go into the barrel (breech end) on the LGU...wondering if the barrels on the LGU are tighter...i think they are going by pellet fit and performance.