As Only War seems to have the most current momentum, I thought it best to share my musings on its forum.
There exist examples of weapons requiring the Exotic or other "specialized" Weapon Training Talents in order to use them without incurring penalties to to-hit rolls. Weapon Training Talents such as Flame, Plasma, Melta, and others, all imply PCs and NPCs must have the appropriate training in order to use these types of weapons to their greatest potential. These types of weapons are not just organized into categories (such as Flame, Plasma, Melta, etc.), they also possess Weapon Qualities of the same designation. As I am wont to do, I picked at this particular thread in the weave and was inspired to take a closer look at other Weapon Qualities, such as Tearing, Devastating and Felling.
One might take the view that weapons such as the humble Chainsword or the noble Boltgun possess the Tearing Weapon Quality as a natural assumption of their operation; Chainswords are fitted with a whirring chain of mono-bladed teeth, and it makes a sort of logical sense that "tearing" is what the Chainsword was intended to do (and does), while the Boltgun's blessed ammunition, mass-reactive bolts, explodes within a target a fraction of a second after penetration, "tearing" the target to shreds of meat and bloody mist. It then appears as if this Quality is simply taken for granted; use these, get this.
But this is not the Weapon Quality that piqued my interest. Personally speaking, I feel the Weapon Training Talents of Chain and Bolt are sufficient to let you know what you're getting when you use those weapons. It was Felling that first stuttered my investigation. The Damage of a Lascarbine and a Long Las are identical, d10+3, and the Long Las has a Penetration value that is one meager point above that of the Lascarbine. Yet the Long Las possesses the Felling (4) Quality, so any rube with Weapon Training Las can pick one up and use it with skill and efficiency equal to the thousands of other women and men in the trenches? Sure, the Long Las also possesses the Accurate Weapon Quality, but so to does the Vanquisher Cannon. Does this mean an Operator with Operate (Ground) knows how to transfer the martial skills she's honed using her Accurate Vanquisher Cannon if she should suddenly find herself using a Long Las? I don't think so.
I strongly feel Weapon Training (Felling) should be added the list of Talents. I'm not meaning to imply I know how I would go about reworking/reorganizing rules to make its inclusion seamless; I hadn't given that thought any consideration of time; only that I feel it makes as much sense as any of the other plainly silly (read as arbitrary) mechanics included in the rules. The Devastating Weapon Quality is not listed in the Only War Core Rules, so I'll include only that my thoughts on it follow likewise. As a short aside: why is it not included in Only War? It's included in Black Crusade. Are the embattled forces of the Periphery immune to devastating weapons?
Additionally, while I was looking at this loose thread regarding Felling, I fell into the absurd logic of Swift Attack and Lightning Attack. These are Talents PCs and NPCs must have if they want to score additional hits on their targets during the course of a melee. These are Talents that require the expenditure of XP, and additionally mandate some prerequisite Skill value and/or Talent. But anybody, even a two-year old Cadian (who can shoot before she can walk? Really? "Well sure", she said in incredulity. "I can put a gun into any wee toddler's hands and it might pull the trigger…") can pick up a Las weapon with the Semi or Full Auto RoF and bang out excess shots? I'm not necessarily as rigid on this topic; I know it's a "Galaxy of Guns" and it's "Only War"; but perhaps someone might look into the inequity of pumping XP into prerequisite Skill values and Talents as opposed to just getting Weapon Training (Las) for free by sheer dint of being some poor habwife drummed into a regimental founding and tell me if it still makes sense? I mean, if I can pick up a Las weapon and fire Semi or Full Auto without rigorous training, I guess a Felling Long Las isn't that far a stretch after all, right? Sure, melees happen. But if you've been trained to use a gun, and only occasionally afix a bayonet, why not just run away? Yeah, yeah…Commissars. Shoot them on Full Auto, then run. All joking aside, as with the various and sundry other silly mechanics, I feel it makes perfect sense that PCs and NPCs would know what they're getting when they pull the trigger for a single shot, but it's taken for granted that Semi and Full Auto fire requires the same level of training; perhaps a penalty to BS Tests akin to off-handed Attack penalties when firing a weapon on Semi or Full Auto if they do not possess a requisite BS value and Weapon Training (Las, Semi-Auto), which itself would be a prerequisite Talent for Weapon Training (Las, Full Auto). All this flip-flopping on Semi and Full Auto fire taking this many or that many Actions and having this penalty or that penalty, when treating it exactly as Swift and Lightning Attack may likely have leveled the playing field with the very first errata released for Dark Heresy. Again, one might simply take the abilities of ranged weapons for granted, but in the context I've presented, my musing makes as much sense as anything else printed between the binding covers of Only War. For that matter, why not simply do away with Swft Attack and Lightning Attack? Why can't a combatant furiously swish her melee weapon about in hopes of striking her target(s) multiple times for no more than a (possible) penalty to her WS? Because it takes a measure of skill to use a melee weapon thusly? Eh?