I have to admit I have failed entirely to print Delrin even with the help of the filament manufacturer and concluded I would have to wait until I upgraded my printer and enclosure meanwhile I have been printing in spectrum. Nylon6 LW our max test pressures aren't as high as yours but we are regularly printing Semi-pressure vessel caps for test pressure internal of 6 to 7 bar.
This material is very easy to print and has properties close to Delrin.