Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

Is this allowed? Does the roll before you scatter the blast count as a to hit roll?

No as it is not a to hit roll.

Thanks, glad I've been playing it the right way

Until the FAQ is official, it does work, as (when used) you have the ability to re-roll To Hit rolls.

Per the FAQ draft (which may or may not change), it is not a To Hit roll, therefore nothing affects it, even though the rules specifically call out the ability to re-roll To Hit rolls.

I presume you mean the Combat Doctrines rather than Chapter Tactics.

As Happy has mentioned, one of the FAQ rulings prevents Preferred Enemy (which is re-rolls of a 1 to hit) from affecting a plasma cannon. This likely means a non-Tactical Squad in a turn you're using a Tactical Doctrine (i.e. re-rolls 1's) won't work, but that a Tactical Squad with a Plasma Cannon (i.e. re-roll all failed to hits) might work (a la Twin-Linked).

Hopefully a more detailed explanation will be included in the final version of the FAQ.