problem with ejection for n0 1mk 3 and no4 mk 1

[Surpmil]

It's probably been said already, but remove the forend so you can see the underside of the receiver and bolt. If you have two with the same problem (and from the same source) you may have someone's attempt to make the rifles inoperable without actually deactivating them.

If you've got empty cases jammed in the chambers as some posts suggest, tap it out with a cleaning rod while someone gently rotates the bolt. If you're not sure what is in the chamber(s) get a gunsmith to deal with it.