First, some clarification. In the entry for the double barrel shotgun, it says you can fire both barrels as one attack, then proceeds to say that a double shot with bullets takes a -4 penalty "on both attacks". So is it one attack or two? The rest of the wording seems to imply one attack to me, though it's not really clear. Would it be a single attack roll with 4d8 + modifiers damage, or two seperate attack rolls as one attack action of 2d8 + modifiers damage?

Next, Vital Strike. Vital Strike says when I use the attack action, I double the dice rolled. As I can fire both barrels of a double barrel shotgun as an attack action, and it says it's "one attack" in the wording, for a total dice count of 4d8 according to the book, would Vital Strike double that to 8d8, and so on with the Improved and Greater Vital Strike

It's considered a single attack even though it uses two attack rolls. Vital Strike should work on both damage rolls as written.

So your interpretation is that as an single attack action (Standard Action), the wielder of a double barrel shotgun makes an attack with each barrel using bullets, rolling the attack (at a -4 penalty) and damage (2d8 + modifiers) seperately for each barrel, for which Vital Strike applies to each shot because they are damage dice as part of a single attack action.

Dang...that just seems really powerful.

Since I've yet to have two people with the same interpretation, I'm going to see if I can get a few more thoughts on the matter.

When using the double shot of a double barrel shotgun:

For the purposes of feats and abilities, is it considered one attack or two? Even the descriptions says "one attack" in one sentace, and "both attacks" in the next sentance.

How exactly is damage calculated? Is it calculated like two completely seperate attacks, each with their own damage modifiers, or one attack with modifiers added once, but the damage dice determined by how many barrels hit?

It "should" be that it is 1 d20 roll, 4d8 damage, with all modifiers only added once, but the wording is far too conflicting to be able to say whats right

From one perspective it makes sense to roll 2 times for a double barrel shotgun, & roll the damage as one attack. The bullets could be packed differently enough to cause one to miss so it would cause either 2d8 or 4d8 depending on the number of shots that actually hit.

And from the other perspective?

IMO vital strike would apply to one bullet, not both.

Each barrel fires a bullet, which is its own attack.

Benefit: Make one attack roll. If the attack hits, the target takes damage from both bolts. Critical hits, sneak attack damage, and other precision-based damage only apply to the first bolt.

Let's use the double crossbow as an example here (which is all I'm going on here). it fires both bolts, but the enhancements/modifications/etc only apply to the first bolt.

I could see a case for both bullets/bolts but this is an admittedly grey area and I'm not set on my tentative interpretation.

IMO vital strike would apply to one bullet, not both.

Each barrel fires a bullet, which is its own attack.

Double Crossbow wrote:

Benefit: Make one attack roll. If the attack hits, the target takes damage from both bolts. Critical hits, sneak attack damage, and other precision-based damage only apply to the first bolt.

Let's use the double crossbow as an example here (which is all I'm going on here). it fires both bolts, but the enhancements/modifications/etc only apply to the first bolt.

I could see a case for both bullets/bolts but this is an admittedly grey area and I'm not set on my tentative interpretation.

Uh...I think you're missing something. Enhancement bonuses, for one, are not precision based damage, and should be added to both bolts in the case of the double crossbow. Only "precision based damage" is limited to the first shot; all other damage is added to both, such as damage from special properties like Flaming, or the Weapon Specialization feat. And while Sneak Attack and Critical Hits are explicitly "precision based damage", various feat bonuses and the like are not nearly as clearly defined. Not to mention with the way Vital Strike details "precision based damage" to me implies that the bonus dice are not "precision based damage" themselves, though are specified to not be multiplied on a critical hit.

The other odd wording here is that it also calls the double shot "one attack", so anything that applies to "one attack" should apply to everyhting involved I believe, based on that wording, as though there are two attacks involved, it still counts as "one attack" by the wording.