That post could have been written by me! I have exactly the same problem and if I find the solution I will let you know a.s.a.p.


Experience to date:
1) As you did, cartridges made up in the manner that apparently works for others - no ignition.
2) Firmed up spring by adding a shorter, harder spring to the one already present - no ignition.
3) Needle seemed to be driving cap into cartridge. Made up firmer cartridge - no ignition.
4) In desperation filled cartridge with hard wad. Needle went right through, leaving cap impaled on needle - no ignition.
5) the impaled cap ignited when fitted to an 1858 Enfield. So primer material was not defect.


The last two items lead me to suspect that the primer material in at least some of the caps is largely deposited around the edge, leaving little to none in the centre.
My next trial will be with a blunt needle to impact a larger area of the cap base.


Any creative comments will be welcome!