Space Marine Chainsword?

[Sam Baughn]

Well my rules are:

Chain-Blades (TL9^)

A chain-blade is basically an advanced chainsaw grafted onto a melee weapon. Chain-swords are the most common in fiction, but chain-axes and chain-halberds have been used as well. Any edged weapon which does cutting damage may be a chain-blade. Versions with rotating blades are also possible and use the same rules.

A chain-blade is 50% heavier than a normal weapon of it's type and has it's ST requirement increased by 20% (round up). It has the same extra cost as a vibroblade and uses the same rules for power consumption and activation. Chain-blades are not compatible with vibroblades, nanothorn blades or monowire blades, although they are available in the usual quality grades.

A chain-blade increases cutting damage by +1d and converts all bonus damage into dice at the rate of +1d for each +1 (so a weapon which did sw+2 cut would do sw+3d as a chainblade). Do not convert quality bonuses to damage in this way.

If a chain-blade is ever broken while running it will explode, causing fragmentation damage equal to it's bonus damage to anyone nearby (so a chainblade which did sw+3d damage would cause [3d] fragmentation).

From this thread, which also includes some other weapon options suitable for the 40k setting: http://forums.sjgames.com/showthread.php?t=67127