Complex sentence: A variant of the XM47 series, which is in the following section, the XM48 is a "skittering" type smoke grenade: the filler is burned internally and vented through ports in the grenade body, making the grenade spin erratically.
Split into simpler sentences: A variant of the XM47 series, which is in the following section, the XM48 is a "skittering" type smoke grenade. What this means is the filler is burned internally and vented through ports in the grenade body, in effect making the grenade spin erratically.