These are the results from my mates tests..
at the lb-age the lead parted from it's clip
Korda......4.5lb
Nash.......4.7lb
Armalead...2.6lb
He also tried a local shop bought clip and that parted at 2.00lb.
The actual shape of the lead clip itself was slightly different to the Armalead and korda..it was a sort of 7 on its side and made from wire not plastic.
The korda and nash were both prone to the swivel pulling out on various occasions BEFORE the lead released from the clip.