So, I've been having a debate with some folks at Advanced Tau Tactica, about whether or not XV8s are truly Relentless, or whether they're unable to move-and-fire with heavy weapons. It's a rather arcane bit of nonsense, particularly since XV8s can't even take heavy weapons outside of Forge World suits, really of interest to none but the most pedantic. Amongst whom, needless to say, I sometimes count myself.
During the course of the debate, however, a rather interesting point was raised. A poster going by Nevar tried to argue against my 'the rules mean what they say' stance by pointing to the entry for the pulse carbine. Seeking to explain why rules that look like they say one thing can actually mean another, he noted that the pulse carbine says that you take a pinning test if you suffer a wound, which he interpreted as 'successfully rolling to-wound with the weapon, regardless of outcome'. I initially pooh-poohed the idea, claiming that wounds didn't actually become wounds until you'd failed a saving throw (or just not been able to make one to begin with), but the strangest thing happened as I started marshalling evidence to justify my stance.
It started to look like Nevar was right.
To understand why, there needs to be some groundwork laid. Codex: Tau Empire came out during 4th edition, and at that time the rules for pinning weapons stated that a unit had to take a pinning test if "the firing of a single enemy unit inflicts casualties with pinning weapons," where 'casualties' was only used to refer to models which were to be removed from the board for having suffered their maximum number of allowable wounds. The 5th edition ruleset clear the language up a bit, with the much more straightforward instruction that "If a unit other than a vehicle suffers any unsaved wounds from a pinning weapon, it must immediately take a Pinning test." And like casualties, 'unsaved wounds' was actually defined by the rulebook, and differentiated from just plain 'wounds'. The tricky part comes in when you look at Codex: Tau Empire, and the entry for the pulse carbine under the infantry wargear section. According to the codex, which it must be remembered takes precedence over the rules in the basic rule book, "Any unit suffering at least one wound from pulse carbine fire must test for pinning."
Note, please, that the carbine does not call for a test after inflicting 'casualties' (4th) or 'unsaved wounds' (5th), but rather simply for wounds. This is the important part.
You see, the crux of my argument surrounding the XV8 has been that the rules mean what they say, even if they seem to conflict with what the basic ruleset calls for. And that being the case, the rules for the pulse carbine are clearly distinct from the rules for standard pinning weapons, under both the 4th and 5th edition rulesets. Those rules, the wording of at least one and possibly both of which would have been known to the writer of Codex: Tau Empire, are specific. It isn't just wounds, which are generated by the 'to-wound' rolls, that count, but a particular subset of those wounds, namely, those that create casualties or go unsaved. By leaving out either of those terms, which could certainly have been squeezed into the available space or simply been omitted entirely for space reasons, the rules for the pulse carbine define the pinning powers of the weapon slightly differently from those given for the basic weapon type in the rulebook. Functionally, this is no different from the way poisoned weapons have a basic value (4+), but also allow particular poison weapons in codexes to assign their own values (such as the 2+ Hellfire shells in Codex: Space Marine).
So, it turns out that even after all these years, a good close reading of the rulebook can still surprise me. And that perhaps arming a few of my Fire Warriors with carbines wouldn't be a bad idea, after all. Carbines will wound most units on a 3+ at worst, after all, and with markerlight support to lower LD values for pinning tests, I may well have an even more solid answer to fast-moving assault units than the community's standard 'throw Kroot in their way' solution. And certainly a more elegant one, I think we can all agree.