Few pics for MrClarke and others...

[Kev G]

The South Africans used and made 20 round magazines with the FN locking lug for their 7.62 converted Brens.
It wasn't until the weapons found there way to Rhodesia that larger capacity magazines were made and converted.Pic attached.

The UK L4A1 7.62 Bren conversion also used the FN locking lug on a 28 round magazine.