When resolving a Combat Encounter, you may gain +2 Strength. If you do, each 6 you roll when resolving a etc etc
If I have a +5 weapon, typically I take the higher bonus as my bonus (they are not added together), and I can use the non-bonus effects on all items I hold. In this case, because it says "If you do", does this mean I must take the +2 Strength as my bonus and nothing higher, even if I have such an item, in order to use the blunderbuss rolling effect stated after?
If you choose to gain the bonus, then you must add 1 success for any 6 rolled (after the rerolls, if applicable) and substract 1 success for any 1 rolled (after the rerolls, if applicable).
But the bonus itself isn't special. As always, you apply the highest available bonus. If it's not the bonus provided by the Blunderbuss, that doesn't affect the other ability in any way.
The choice to gain the bonus activates the other ability, not the fact of applying the bonus.
The card could be as well written like this:
When resolving a Combat Encounter, you may gain +2 Strength. If you do gain the bonus, each 6 you roll when resolving a etc etc
Edit: I have asked Nikki Valens - Eldritch Horror's designer, for an answer.
Here it is, with emphasis added in the most relevant part:
The blunderbuss has a potencial negative effect in that rolling 1’s will negate successes. It may be that an investigator does not wish to use this effect. For this reason, the bonus and the other effect are tied to an option on the investigator’s part. The investigator may choose to both gain the bonus and the other effects (6’s are two success and 1’s negates successes). Even if the investigator applies a higher bonus from another effect, the 6’s and 1’s will still be affected. Please note however, the choice to use the effects of the blunderbuss must be made before dice are rolled.
The card is quiet clear: If you do. If you do not use the +2, then you cannot use the special ability. This does make the blunderbuss less useful than the shotgun.
There seem to be some confusion in what I mean. I read
When resolving a Combat Encounter, you may gain +2 Strength. If you do, each 6 you roll when resolving a combat encounter counts as two successes.
To mean
When resolving a Combat Encounter, you may gain +2 Strength. If you gain +2 Strength from the Blunderbuss, each 6 you roll when resolving a combat encounter counts as two successes.
I read may as an invitation to either do it or not. You have a choice whether to apply the bonus or not.
If I have a knife that grants me +3 Strength and I use that bonus, then sixes do not count as double successes. If I chose to not use the knife but instead use the +2 from the Blunderbuss, then all sixes rolled are double successes.
This follows the golden rule of cooperative games:
If a rule can be interpreted in several ways, the right one is the least helpful to the players.
