If you want to use a modern bayonet for the Sa58 rifle, you have to mount this end piece on the barrel. It is CNC made of steel monoblock (no casting). Of course there is easy installation with the enclosed screws. To install the bayonet, you will also need a compensator with a suitable diameter (Extrema, Supermini, Etc.).
This will make the Sa58 rifle fully compatible with a range of modern bayonets and assault knives, and its utility value will move up again.
Detonics PIRAD 2015
US M-9 Bayonet
USMC Multi Purpose Knife
CZ 805 Bren