When it comes to shooting, 3 is often the magic number for firepower. Most units in the game have 3 armor at the most, so you’ll rarely need more than that to destroy the majority of units you’ll be facing. Unfortunately, not too many Orkz come with more than 2 firepower.
Enter the humble Gretchin. Various Gretchin cards have been printed throughout 40K CCG sets, and generally follow a flavourful design pattern of being non-flag units that either play a support role or represent Gretchin being shot/blown up/sacrificed for the benefit of the Orkz. While I’m a big fan of defensive Gretchin like Gretchin Mob, offensive scaling cards like Ammo Grotz can quickly get out of hand, especially at large sector battles.
Even one Ammo Grotz at a sector can turn the tide of a battle. It can bump your Veteran Skarboyz and Goff Boyz to 3 firepower so they can start dishing out the hurt without needing additional tactics. Ideally, though, you’d prefer one Ammo Grotz and one Gretchin Mob at the same sector, for the additional firepower boost as well as the added protection for your Ammo Grotz (which your opponent will presumably want to target first).
Ammo Grotz are otherwise generally useless in combat unless you have additional firepower boosters like Looted Demolisha (one more reason why multiple Ammo Grotz at a sector becomes kind of nutty) or you need a sacrificial body to protect your Gretchin Mob and its static ability. The die roll is fair but not exciting, and the command line will vary in helpfulness depending on how many non-flags you run in your deck.
Right now I’m running 4 Ammo Grotz and 4 Gretchin Mob in my own Ork shooty infantry deck, and I can’t imagine replacing either one. They synergize so well with each other and add some real bite to your run-of-the-mill Orkz.
And when you have a fistful of Orkz and a fistful of BAs, run of the mill is good enough!