You're right there Brian. Even the correct magazines would malfunction in some L42's due to the newly machined recess for the front feed lips (they're not feed lips really but retainers......) not being deep enough. This was evident because the magazine would rock on the front lips - as it will when the magazine well isn't machined. Rock the magazine to the rear so that it clicks into place and the nose of the mag drops slightly causing a misfeed. Something that a sniper could do without. If the rear strap was adjusted so that the nose of the magazine was in its correct feed position, then the rear would be slightly low and the face of the bolthead would just slip over the top round in the magazine, leaving you thinking that you'd actually loaded a round when you hadn't. Something else that a sniper didn't really need either! It also meant that the magazine was loose .................., something that the Armourers didn't need either!
The smaller base rim diameter oif the 7.62mm case against the .303" case was its downfall as even when fully adjusted, it was touch and go whether the bolt head would actually pick the rear of the round up on the forward 'load' movement
Anyway, that's why a small sketch was subsequently issued (I think it was in the miscellaneous instructions section) advising of the problem and the remedy. To be brutally honest, after a few years of the L42, you could start to see that it was an 'on the cheap' project. Starting with the woodwork. As for the person who advised that it could be cheaper if existing stocks of No8 handguards could be used.........., well...., words fail me!