Ere we go! Culler's How to Build an Ork Army part 5: Fast Attack!

-Old School here, with another addition from Culler's How to Build an Ork Army Tactica:

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-Stormboyz with a powerklaw nob are a good choice. The bosspole is pretty much required due to their max size being low and them being a prime target.

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-Warbikers are another good choice. A nob with powerklaw and bosspole is pretty much required. I prefer them to stormboyz since they have a devastating shooting option as well as being able to fight well in CC. Stormboyz do a little better in assault though, and are half the cost albeit not as tough and virtually no save to the warbikers’ 4+ cover and 4+ armor and 3+ cover when turboboosting. Stormboyz can charge into cover without dangerous terrain checks though. It comes down to preference.

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-Deffkoptas are somewhat of a wild card. You can turbo-boost them in front of everything in your army to have them soak up a round of shooting from your enemy. 2 wounds each, T5, and a 3+ cover save is pretty solid. On the other hand, they’re surprisingly weak in CC. Tough yes, but only 2 attacks each base at strength 3 unless they charge. They’re decent vehicle hunters, though expensive. Each basically has a 55% chance of hitting with each shot they fire. For anti-infantry there are better options (like warbikes). As far as upgrades go, there are many different ways to equip them for whatever you want them to be doing. The only upgrade I strongly discourage is the kustom mega-blasta. It's pricey and not twin-linked like the other weapon options, so you won't hit the broadside of a barn with it.

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-Warbuggies are decent if you have a bunch of vehicles. Because in a list where they’re the only vehicles they are too vulnerable to survive your opponent’s focused anti-tank for long. They can’t outflank like deffkoptas or ignore terrain like deffkoptas and can’t tie up ranged specialist squads like deffkoptas but are pretty tough for their points if you have other vehicles as well. Their optimal role is probably tank hunting in a mechanized list, though skorchas can pull off some pretty great stuff now and then in a mechanized list. Giving them big shootas is a good option if you’re hurting for anti-infantry ranged firepower. Keep them as low points as you can though and don’t worry about upgrades.