The Crossbow weapon group has 25 gems in its cutting pool — the widest of the eight groups, one more than Occult, Bow and Elemental and four more than Quarterstaff. Of those, only 17 skill gems in the whole game carry the Ammunition tag, and their bands run all the way from 1 to 13.
That mismatch is the first thing a crossbow build has to understand. The cutting pool and the ammunition pool are not the same set. The pool contains grenades and ballistas that are not ammunition skills, and it excludes some ammunition skills entirely. Plan from the 25, not the 17.
The 25-gem Crossbow cutting ladder
| Tier | Gems in the pool | Count |
|---|---|---|
| 1 | Explosive Grenade, Permafrost Bolts, Fragmentation Rounds, Armour Piercing Rounds | 4 |
| 3 | Flash Grenade, High Velocity Rounds, Incendiary Shot | 3 |
| 5 | Galvanic Shards, Ice Shards, Gas Grenade, Rapid Shot | 4 |
| 7 | Artillery Ballista, Glacial Bolt, Explosive Shot, Voltaic Grenade | 4 |
| 9 | Oil Grenade, Siege Ballista, Stormblast Bolts | 3 |
| 11 | Hailstorm Rounds, Shockburst Rounds, Emergency Reload, Mortar Cannon | 4 |
| 13 | Siege Cascade, Plasma Blast, Cluster Grenade | 3 |
The pattern is 4, 3, 4, 4, 3, 4, 3 — never fewer than three options, never more than four. Compare that with Quarterstaff, which drops to two options at tiers 11 and 13, and the practical effect is that a crossbow character can always cut a tier 13 gem and land on one of three usable results.
The pool also mixes three different skill families. Rounds (Fragmentation, Armour Piercing, High Velocity, Permafrost, Incendiary, Galvanic Shards, Ice Shards, Glacial Bolt, Hailstorm, Shockburst, Plasma) are the ammunition core. Grenades (Explosive, Flash, Gas, Voltaic, Oil, Cluster) are a separate delivery system. Ballistas and cannons (Artillery Ballista, Siege Ballista, Mortar Cannon) are a third, with Emergency Reload as a utility outlier.
A build that commits to rounds is using roughly 11 of the 25 pool entries. The other 14 are either a different build or dead cuts.
The 17 Ammunition skills, by band
| Band | Ammunition skills |
|---|---|
| 1 | Armour Piercing Rounds, Crossbow Shot, Fragmentation Rounds, Permafrost Bolts, Requiem |
| 3 | High Velocity Rounds, Incendiary Shot |
| 5 | Galvanic Shards, Ice Shards, Rapid Shot |
| 7 | Explosive Shot, Glacial Bolt |
| 9 | Stormblast Bolts |
| 11 | Hailstorm Rounds, Shockburst Rounds |
| 13 | Plasma Blast, Siege Cascade |
Five of the 17 sit at band 1, and three of those five are in the tier 1 cutting pool. That is a good opening hand: Armour Piercing Rounds for physical, Permafrost Bolts for cold and Fragmentation Rounds for area clear are all available at character level 1, before you have spent a single passive point.
Band 13 is where the pool narrows to two — Plasma Blast and Siege Cascade — and both are channelled or sustained rather than fire-and-forget. The two highest-band ammunition skills are also the two that lean on channelling or sustained fire rather than fire-and-forget shots.
The 11 ammunition supports
| Support | Band | Colour |
|---|---|---|
| Arjun’s Medal | 1 | Green |
| Auto Reload | 1 | Red |
| Double Barrel I | 1 | Red |
| Ratha’s Assault | 1 | Green |
| Ammo Conservation I | 2 | Green |
| Double Barrel II | 2 | Red |
| Streamlined Rounds | 3 | Green |
| Ammo Conservation II | 4 | Green |
| Nimble Reload | 4 | Green |
| Ammo Conservation III | 5 | Green |
| Double Barrel III | 5 | Red |
Eleven supports is a thin pool — for comparison, 108 supports carry the Attack tag and 58 carry Projectile. Only 11 are ammunition-specific, which means a crossbow build spends most of its sockets on generic Projectile and Attack supports and treats the ammunition line as the specialised top layer.
The colour split matters more than the count. Five green, six red, zero blue. A crossbow setup needs red and green sockets almost exclusively, so intelligence gear is close to dead weight for this archetype.
Two rank lines dominate: Ammo Conservation runs I, II, III across bands 2, 4 and 5, all green, and Double Barrel runs I, II, III across bands 1, 2 and 5, all red. That is six of the eleven supports in two families, which means the ammunition support pool is really “two lines plus five singletons”.
The full text of the band-2 entry shows how specific these get:
“Ammo Conservation I — Supports Crossbow Ammunition Skills, granting a chance to not consume a Bolt when firing.” — poe2db.tw support gem entry, cached in
src/data/poe2-support-gems.json
Note that it supports Crossbow Ammunition Skills — not Projectile skills, not Attack skills. A grenade skill does not qualify. This is the clearest example of why the 25-gem pool and the 17-skill pool diverge: half the cutting pool cannot use half the ammunition supports.
Sockets and the band-5 squeeze
The gem ladder caps the build: 2 sockets at gem level 1, 3 at gem level 10 (character 36), 4 at gem level 15 (character 64), 5 at gem level 20 (character 90).
A crossbow character wants at least two ammunition supports, because Ammo Conservation and Double Barrel are both rank lines that improve with rank rather than replacing each other. At character level 36 you have three sockets total — one skill, two supports. At level 64 you have four. Only at level 90 do you get five.
That is why band 5 being the endpoint of both rank lines is awkward. Ammo Conservation III and Double Barrel III both need gem level 5, which is available early; but slotting both rank III versions plus a main skill is a five-socket proposition you cannot reach until character level 90.
The realistic mid-game configuration is one ammunition skill, Ammo Conservation II and one generic Projectile support. Everything else waits.
A build order that follows the table
Character level 1: pick from the tier 1 four. Fragmentation Rounds for clear, Armour Piercing Rounds for single target, Permafrost Bolts for cold. All four tier 1 options are ammunition or grenade skills, so no cut is wasted.
Character level 10: add Ammo Conservation I. Band 2, green, and it fits inside the two sockets available at gem level 1 — but only becomes worth a slot once you are firing enough bolts for the conservation chance to matter.
Character level 36: third socket, second support. This is the point where Double Barrel II (band 2, red) or Streamlined Rounds (band 3, green) enters.
Character level 52: tier 13 access. Gem level 13 needs character level 52, which opens Skeletal Brute-style endgame options in other groups — for crossbow, it opens Plasma Blast and Siege Cascade as ammunition skills and Cluster Grenade as a pool option.
Character level 64: fourth socket. Now both rank II supports fit alongside the skill.
Character level 90: fifth socket. The only point at which the full ammunition support suite is legal.
Mercenary themes, and what they imply
The class table gives the Mercenary exactly three themes: Ammunition, Elemental Rounds and Versatile Range. That is unusually on-the-nose for this weapon group — two of the three themes name the ammunition system directly.
The third, Versatile Range, is the one that shapes play: the class table describes a character that picks enemies off from afar and destroys anything that gets close. For a crossbow build that translates into carrying both a single-target round and a clear round, which is exactly what the 17-skill pool supports at band 1.
For the surrounding systems, the support gems guide covers all 557 supports by band and colour, the uncut gems guide explains the 20 gem levels behind the socket ladder, and the skill gems database lists every Ammunition entry with its tags.
The Mercenary class guide covers the class in more depth, the ascension guide explains the level 22 gate, and the endgame guide picks up once the fifth socket is in reach.