You seem to be assuming that the pressures touching piston/cylinder from the Delrin bearings and the metal bell bearing are the same but a precisely machined and hand finished piston and a central piston rod would hardly touch the moly lubed cylinder so even if plastic has less friction there would be still be more friction because the plastic rings would be touching with a even pressure all through the piston stroke, thats why precision made metal parts have less friction in a springer but would cost a more so it is much more easy to manufacture pistons with rings as they can hide any small faults and look like out of the box tuned guns. And metal parts look better when you dismantle your gun and will last a lifetime unlike plastic parts
Are you sure that you have posted a picture of two German pistons and not Bulgarian
Why do Diana insist on pressing/folding/forcing metal roughly into shape rather than actually machining it?
The typical size of the rear bearing on an LGV or TX is 29.95mm running in a 30mm cylinder so there is no radial pressure exerted from the bearing onto the cylinder walls as it's a clearance fit.
With the piston seal removed the bearinged piston is an easy push fit along the cylinder, if the cylinder is in the horizontal plane the only thing inducing friction in the cylinder is gravity acting on the piston's mass.
A precisely finished metal piston running on moly grease will still scuff on the cylinder walls and will still resonate in use, the use of moly grease won't stop this, but it will introduce drag on the piston.
The use of Delrin piston bearings is not to hide faults such as scuffing and resonance, it's to prevent them occurring in the first place.
It's so easy to use the word shit about something when you don't have to discuss and prove what you are saying, is your idea of shit a stronger cocking link that don't break compared with a quality link that does break and a machined one piece compression tube that can't leak compared to two piece tubes that can leak ?
Is this your idea of quality plastic and more plastic
I use the word shit when a manufacturer has a well documented history of making out of round Pistons, Pistons that fail and release the latchrod, cocking arms which fail so frequently that they have to change the design, substandard barrels made in China, plastic trigger components, drooping barrel etc etc etc --- I don't need to prove any of this as it's been well documented by yourself both here and on the DWC.
The compression tube you hold so dear I view as a cost cutting exersise to save on machining costs giving no realistic advantage over well made two piece compression tubes.
And after fifty years of trying Diana still haven't come up with a trigger to equal a Rekord, true they've come up with one that's easy to strip, but that's only to save folks time in changing out the broken Sears which you have shown us.