I have just across this thread and am utterly horrified. The ratworks and Fenton aluminium cylinders look similar and appear to be aluminium versions of the HW cylinder but without the sections of reduced outer diameter and do not have the design weakness (fuse) of the A&M one. I agree with the various stress calculations that have been posted that show that pressures around 650bar are going to take the material up to its 0.2% proof stress and will leave it with a permanent set. If the alloy is 6082 T6, its burst stress is not much higher than its 0.2% proof stress.

I'm not familiar with the testing requirements for pressure vessels, but surely we would expect the manufacturers to proof each cylinder sold to 1.5 times its working pressure (so 375bar if intended to be fitted with an internal reg) and conduct a hydraulic burst pressure test from a sample of each material batch.

Another failure of the kind seen here is certainly going to alert the attention of the ban everything brigade.