Silencer
Silencer is the definitive part of most one-Weapon builds, but in the case of
Double Barrel it's actually not quite as critical. With a base Cooldown of three seconds, the extra reduction is not nearly as necessary compared to the many other solo Weapons.
Despite that,
Silencer is still a welcome inclusion and will always justify its place on the board. Though in some cases you may want to opt to place it somewhere else in order to free up an "adjacent slot" next to
Double Barrel.
Ramrod is absolutely necessary on one side, but depending on the other items you find, there's a fair argument to be made for placing something else on the other side instead of
Silencer. After all, you still get the Cooldown reduction. Sitting on its right side only affects the Damage.
Kripp was super lucky with his random enchant, having it apply Shiny to his
Silencer. This granted an additional 25% Cooldown reduction which is essentially like having two
Silencers.
Sextant
Sextant is mostly here as an efficient source of Haste. You'll usually have a solid foundation of Crit Chance, and so the added adjacent Crit just isn't necessary. However, if you are lacking Crit, feel free to swap its position with
Silencer.
Be sure to get it to at least Gold tier in order to reach two second Haste duration. Two seconds makes a huge difference when it comes to stacking Haste triggers. Alternatively, look for a pair of
Rocket Boots at The Curio.
Flurry of Blows
Flurry of Blows gives this build the potential to have a more explosive opener. Ideally the Charges fuel the
Double Barrel (and not
Ramrod) to essentially unload multiple shots within a few seconds.
This can help trigger any Freeze skills and deal a bunch of Damage before the opponent has the chance to respond and/or scale. With the Shielded enchant it also helps give you a buffer to hopefully keep out of one-shot reach.
Left-Handed / Right-Handed
Left-Handed and/or
Right-Handed are both excellent flat Damage boosts for a single Weapon. It's important to make sure your Damage is much higher than its base form, as you're relying on a single source of offense.
It's also necessary to make up for the lower Gold/Diamond tier values. The particular Damage skill is generally irrelevant. It's just a matter of finding the most raw stats available for the cost, and these two offer exactly that.
Tempering / Improvised Weaponry
Tempering gives the build a much needed form of Damage scaling. This is a pretty reliable skill that works great during the earlier days with multi-Weapon setups, as it doesn't rely on anything but the item being used.
For late game options,
Improvised Weaponry is definitely the premium skill to look for, provided you have a reliable amount of Crit. And given that you've pivoted to a one-Weapon setup, nine times out of ten you'll be ready, because your build depends on it!