Yes i suppose any thermoplastic will work but there are plastics on the market that are made for their low friction properties, so if one of those were used then the bolt pull could be very light. Combine it with a teflon cylinder and it could be ridiculously smooth, to the point where the only resistance is the spring itself.Good point.
Honestly I don't know what kind of plastic it is precisely.
It is really smooth and clean.
Feels like the plastic used to make book covers, or photo covers.
I just went to a brico and cut a piece from a roll, btw I will suggest that any kind of smooth plastic will work if you lube it with silicone spray.
I said tolerance because I meant tolerance. the supplier I found for the nylon-6 and acetal (Delrin) tubes offers a 25mm ID but with a tolerance of 23mm to 24.4mm ID with the idea that you finish it to your requirement yourself. Hardly precision engineering. if it came as 24.4 guaranteed i would snap it up. Also have a huge 5.5mm wall thickness so much machining would be required.....the hunt continues.Regarding the tolerances (though diameter would be a more correct term here) - I left the same diameter as on original rings. Cylinder head acts as a base surface with hop up unit. So some clearance between rings and cylinder is not an issue. That gap even helps to reduce friction.
Thanks for the advice, i will look for this too.Teflon is kinda soft as raw material. Nylon/PA6 isn't the best option for sliding. I used Ertalyte for receiver glide rings and piston glide rings. Now the bolt pull with teflon cylinder is very smooth. SPR380 spring feels like M150.