I notice that the rate of fire for a Plasmagun is S/2/-, with the Maximal quality. Reading the Maximal quality seems to imply that it is used in conjunction with single shot, but it isn't stated explicitly. Can you semi-auto Maximal shots?

Y'know, apart from the fact that you might burn your arm off.

Without access to my [Only War] supplies, [Dark Heresy Second Edition] seems to be in the same boat. However, do note that Maximal imparts the [Recharge] Quality, which excludes Semi-Auto by dint of its own effect.

In summation, because Recharge disables Semi-Auto and Maximal adds the Recharge Quality, using the Maximal Quallity disables Semi-Auto too. Does that help?

ADDENDUM: Moved to my later post.

Recharge in the Only War Core Rulebook prevents the weapon from firing every round, but does not explicitly disable semi-auto. The specific entry is as such:

Recharge

Because of the volatile nature of the weapon's ammunition or due to the way it fires, the weapon needs time between shots to Recharge. The weapon must spend the Round after firing building up a charge and cannot be fired - in effect, the character can only fire the weapon every other round.

'Between shots' could be read as no semi-auto, but it seems to be an interpretation issue.

Beyond that though, the Integrated Weapon rules in Shield of Humanity remove the Recharge quality from integrated plasma weapons, creating one case where Recharge is not a limiting element.

Aye. I came to the same conclusion shortly after I posted:

On second thought, looking at some other weapons/considering semantics... One might argue that Recharge does not necessarily disable Semi-Auto. In that case, I would allow Maximal Semi-Auto shots, but temporarily lower the threshold on Jams/Overheats or make the player roll for Overheat before each shot. Something to increase the risk of double-Maximals, in any case.