Weren't these designed for the heavy barrelled version of the SLR, itself based on the heavy barrelled FN.
From wiki:
A variant named
L2A1/C2A1 (C2), meant to serve as a
light machine gun in a support role, is also capable of fully automatic fire. Differences from the L1A1/C1 include a heavy barrel, squared front sight (versus the "V" on the semi-automatic models), a
handguard that doubles as a foldable
bipod, and a larger 30-round magazine although it could also use the normal 20-round magazines. Only Canada and Australia used this variant.
L2A1
View attachment 555383
The FN version.
View attachment 555384