The best ammo in Arena Breakout: Infinite is whatever round sits one Pierce Level above the armor you expect to meet — and in Season 7: Utopia (live since September 16, 2026) that answer changed, because Morefun removed the random-penetration lifeline that let under-tier rounds occasionally punch through Class 5 and Class 6 plates. Ammo, not your gun, decides most ABI fights: the same M4 kills instantly with the right round and bounces harmlessly off a high plate with the wrong one. This guide breaks down the Pierce Level system, what Season 7 changed, and the exact ammo tiers worth loading for Normal, Lockdown, and Forbidden Zone raids.
Quick answer: Match your round's Pierce Level to the Armor Class you expect. In Normal mode (now capped at Tier 4 and below in Season 7) a solid Pierce Level 4 round — the classic budget pick like M855A1 or BP — handles almost everything you will face. In Lockdown (capped at Tier 5 and below) step up to Pierce Level 5 ammo for your primary. Forbidden Zone is where top Pierce Level 6–7 rounds (e.g. 7.62×54mm 7N37, Pierce Level 7) earn their price, and after Season 7 they matter more because the old low-chance penetration against Class 5/6 armor was deleted. Flesh damage against legs/limbs is still the budget counter to over-tier armor.
This article is verified against the official Season 7: Utopia patch notes (Steam, September 15, 2026) and the Season 6: White Nights balance notes (June 23, 2026). ABI rebalances ammo and armor every season, so everything below is stamped Season 7 (September 16, 2026) — re-check at the next season boundary.
How ammo works in Arena Breakout: Infinite
ABI does not have a simple "damage number wins" system. Every round carries two stats that matter against armored players, and new operators lose fights for weeks before they learn the difference:
- Penetration — the raw numeric stat printed on the round.
- Pierce Level — the tier derived from it, which is what the game actually compares against armor. The community formula (sourced from the Arena Breakout wiki Penetration page and the official ammo chart) is Pierce Level = floor(Penetration ÷ 10): a round with Penetration 47 is Pierce Level 4. The official chart lists Pierce Level 0–7, with raw Penetration values spanning roughly 1–71 and 7.62×54mm 7N37 sitting at the top as Pierce Level 7.
The interaction rule is the whole game (this part is community-wiki sourced — no official damage table exists, so treat the exact percentages as directional):
- Pierce Level higher than Armor Class → the round almost always penetrates for close to full damage.
- Pierce Level equal to Armor Class → partial penetration, roughly ~80% damage, with the penetration chance depending on where the raw Penetration sits inside that level band.
- Pierce Level below Armor Class → penetration chance drops off fast, with damage decaying toward roughly ~50% when you are several levels under.
Two more columns decide whether a "good" round actually kills: Base Damage (flesh damage once the round is through) and Armor Damage (how much durability each hit chews). A round can be a superb armor-breaker and a poor killer, or vice versa — which is why the "best ammo" is a loadout decision, not a single pick.
What Season 7: Utopia changed about ammo
This is where every stale guide is now wrong. The official Season 7: Utopia combat balance pass — shipped verbatim in the September 8 reveal and the September 15 "Season 7 UTOPIA Arrives" live post — made four changes that rewrite ammo priorities:
- Removed T5/T6 Armor Penetration RNG. Previously, under-tier rounds had a small random chance to slip through Class 5 and Class 6 plates. That lifeline is gone. Under-tier ammo against top armor now reliably fails — so bringing the correct Pierce Level matters more than it ever did.
- Mode-Based Ammo and Gear Cap. Morefun stated it plainly: "Normal: T4 and Below, Lockdown: T5 and Below." You physically cannot bring Tier 5+ ammo or gear into a Normal raid, or Tier 6 into Lockdown. This hard-caps the arms race per mode.
- Increased Effective Range and Increased Headshot Effectiveness — Morefun: "headshots now offer slightly greater rewards relative to body shots" and "The overall TTK has been appropriately lengthened." Headshots bypass body armor entirely, so a cheaper round to the head still beats an expensive round into a plate.
- Season kits + new ammo crafting. Season 7 added experimental Season Kits that "fundamentally change corresponding weapons" (e.g. the MPX Vulcan barrel that "provides the MPX with flesh damage ammo branch options"), and new crafting uses for misc items — "pocket watches, workman's diaries, gas analyzers, etc., can now be used to craft ammo." These kits are removed at the end of the season.
The practical takeaway: pick ammo for the mode you are loading into, not from a flat "best in game" list. A Tier 6 round is dead weight you cannot even equip in Normal.
Best ammo by raid mode (Season 7)
Because of the mode-based cap, the right question is "best ammo for this mode." Here is how to think about each:
Normal (capped at Tier 4 and below). Your ceiling is Pierce Level 4, and that is plenty — most operators you meet in Normal are not wearing Class 5+ plates anyway. A dependable Pierce Level 4 round such as M855A1 (5.56×45) or BP (7.62×39) is the widely-cited budget sweet spot. It penetrates the Class 3–4 armor common in Normal and leaves enough flesh damage to finish the fight.
Lockdown (capped at Tier 5 and below). Now you will meet Class 5 plates, and thanks to the removed RNG your Tier 4 round will not luck through them anymore. Step your primary up to a Pierce Level 5 round so you are trading even or better against the armor you face. Keep a flesh-damage option for limbs.
Forbidden Zone (no mode cap). This is the only place the top of the chart earns its cost. Pierce Level 6–7 rounds — topping out at 7.62×54mm 7N37 (Pierce Level 7) — are what reliably crack Class 6 armor now that the random penetration against Class 5/6 is gone. Expect everyone to be well-equipped; under-gunning here is how you feed your reds to a squad.
Three rules that beat raw Pierce Level
Pierce Level is the headline, but these three factors win fights the chart does not show:
- Shoot durability, not just class. Every armor piece has a durability pool that drops as it is shot, and the lower the current durability, the higher the chance a round passes through regardless of level. This is why "keep shooting the same plate" works — your third round through a chewed vest penetrates where the first bounced. A cheaper round that chews Armor Damage fast can set up a kill for your next shot.
- Aim where there is no armor. Armor in ABI covers the chest and abdomen; it does not cover arms, legs, or (for most helmets) the lower face. Against an over-tier plate, legs and limbs with a high-flesh-damage round bleed a target out faster than hammering their ceramic. Dum-Dum-type rounds that trade penetration for flesh damage exist for exactly this.
- Headshots ignore the whole equation. With Season 7 increasing headshot effectiveness, a Pierce Level 4 round to the head still drops a Class 6 operator. If your aim is good, you can run cheaper ammo than the "meta" chart suggests and win on placement.
How to read the in-game ammo chart yourself
ABI's charts and third-party scrapes go stale within weeks of every balance pass, so the durable skill is reading the stats in the client:
- Open any ammo item card. Note its Penetration value and divide by 10 for its Pierce Level (floor it — 47 → Pierce Level 4).
- Compare that Pierce Level to the Armor Class you expect in your mode (Normal → mostly 3–4, Lockdown → up to 5, Forbidden → up to 6).
- Check the Base Damage and Armor Damage columns. High Armor Damage = good breaker; high Base Damage = good killer. You want one of each thinking in your mag, or a round that balances both.
- Confirm the mode cap. In Season 7, Normal will not let you equip Tier 5+ and Lockdown blocks Tier 6 — so filter your shortlist by mode before you buy.
A note on numbers: Morefun has not published a per-caliber Season 7 ammo table, and no official source lists exact Penetration figures round-by-round. Any chart claiming precise Season 7 values is third-party and unverified — use it as a starting point, then confirm each number against the item card in your own client. The mechanics above (Pierce Level formula, the removed T5/T6 RNG, the mode caps) are all from official sources and are the parts that do not drift.
Where to spend your Koen on ammo
Ammo is a recurring cost, not a one-time buy, so a few economy habits keep you in good rounds:
- Buy mid-tier in bulk, top-tier by the mag. Pierce Level 4 ammo is cheap enough to stockpile for Normal farming; save your expensive Pierce Level 6–7 rounds for the raids that justify them.
- Barter for ammo where you can. Contact barter trades sometimes hand over ammo or modded weapons roughly a Loyalty Level earlier than straight Koen purchase — a real edge for gearing up affordably.
- You earn Koen, you don't buy it. Since the 1.0 launch (September 2025) Morefun removed the ability to buy Koen with real money, so every round you fire is funded by loot, Market sales, and barter. Budget your ammo the way you budget your raids.
FAQ
What is the best ammo in Arena Breakout: Infinite right now? There is no single best round — it depends on your raid mode. For Normal (Tier 4 cap) a Pierce Level 4 round like M855A1 or BP is the budget sweet spot. For Lockdown (Tier 5 cap) run a Pierce Level 5 primary. For Forbidden Zone, top Pierce Level 6–7 ammo such as 7.62×54mm 7N37 is what reliably penetrates Class 6 armor after Season 7 removed the under-tier penetration RNG.
What does Pierce Level mean in ABI? Pierce Level is the armor-penetration tier of a round, derived from its raw Penetration stat (community formula: Pierce Level = floor(Penetration ÷ 10)). It runs from Pierce Level 0 to 7. The game compares your round's Pierce Level against the enemy's Armor Class to decide how much damage gets through.
Did Season 7: Utopia change ammo and armor? Yes. The official Season 7 balance pass removed the random penetration chance against Tier 5 and Tier 6 armor, added a mode-based gear cap (Normal: Tier 4 and below, Lockdown: Tier 5 and below), increased effective range, and increased headshot effectiveness. It also added experimental Season Kits and new ammo-crafting uses for misc items.
Why does my ammo not penetrate high-tier armor anymore? Before Season 7, under-tier rounds had a small random chance to slip through Class 5/6 plates. Morefun removed that RNG in Season 7: Utopia, so ammo that is below the target's Armor Class now reliably fails to penetrate. Bring a round whose Pierce Level matches or exceeds the armor you expect.
Can I use any ammo in any mode? No. Season 7 added a mode-based cap: Normal raids are limited to Tier 4 and below, and Lockdown to Tier 5 and below. You cannot equip Tier 5+ ammo in Normal or Tier 6 in Lockdown. Forbidden Zone has no cap.
How do I beat armor without expensive ammo? Aim for unarmored areas — legs, arms, and the face — with a high-flesh-damage round, or keep firing at the same plate to grind its durability down (lower durability raises your chance to penetrate). Headshots bypass body armor entirely, and Season 7 made headshots slightly more rewarding.
Want to go deeper on the gear side of this equation? Read our Arena Breakout Infinite best armor guide for Season 7 and the full ammo and armor Pierce Level breakdown. For more Arena Breakout: Infinite guides, browse the timesaver.gg blog.
