Boom Brothers is one of NetEnt's earlier releases, a 5-reel, 3-row slot with 20 paylines that launched around 2011. It runs at 96.4% RTP with low volatility, making it one of the more session-friendly games in the back catalogue. The theme centres on three dwarf brothers mining underground, with dynamite, minecarts, and gemstones filling the reels.
The visual style is cartoon-bright with a steampunk edge - gears turning in the background, dwarves hammering away at rock faces, and an underground cavern that stretches behind the reel frame. It is a game from an era when NetEnt was still building out its feature library, and the mechanics reflect that: simpler than modern releases, but with a few ideas that hold up well enough to keep the game in active circulation over a decade later.
Wild and Scatter Symbols
The Wild symbol is represented by the Boom Brothers logo and substitutes for all regular symbols on the reels. It does not replace the Scatter or the bonus Train symbol, but it pulls its weight in the base game by completing combinations across the 20 paylines. Wilds can appear on all five reels, and during the Free Spins feature they appear stacked, which changes their impact significantly.
The Scatter symbol - a red dynamite barrel - triggers Free Spins when three or more land anywhere on the reels. Three Scatters award 8 free spins, four award 16, and five award 32. All wins during Free Spins are multiplied by 2x, and the Stacked Wilds that appear during this feature make it possible to cover entire reels with substitution symbols, creating the best multi-line wins the game can produce.
Free Spins with Stacked Wilds
Free Spins are where Boom Brothers produces its most interesting moments. The Stacked Wild mechanic means that Wild symbols arrive in vertical blocks rather than as single symbols scattered across individual positions. A fully stacked Wild covering an entire reel acts as a universal substitute for every payline passing through it.
Combined with the 2x multiplier on all Free Spins wins, a session where Stacked Wilds land on two or more adjacent reels can generate payouts well above anything the base game delivers. The multiplier is fixed at 2x throughout - it does not escalate - but the consistency of the multiplier paired with the stacked symbol coverage gives the Free Spins feature a reliable uplift over base game play.
Retriggering is possible. Landing three or more Scatters during Free Spins adds another batch of free spins to the total. The retrigger follows the same 8/16/32 structure as the initial trigger.
Train Feature
The Train Feature is Boom Brothers' bonus round and the most distinctive part of the game. It triggers when three Train symbols land on reels 1, 3, and 5 simultaneously. The screen transitions to a rail track where three minecarts - one for each dwarf brother - sit ready to race.
You pick one of the three dwarves, and the carts roll along the track, stopping at various points to collect coin prizes. Each stop reveals a multiplier or a coin value, and the total accumulates as your chosen cart progresses. The round ends when the cart reaches the finish line. The other two carts also complete their journeys, and you can see what you would have won with different picks - a touch that adds a bit of theatre to the outcome.
The Train Feature sits outside the normal reel mechanics entirely. It is a self-contained bonus game with its own prize pool, and the payouts from it are added to your balance independently of any payline wins.
Second Chance Feature
Boom Brothers includes a Second Chance mechanic that can activate when you narrowly miss triggering either the Free Spins or the Train Feature. If two of the three required Scatters or Train symbols land on the reels, there is a random chance the game will nudge a third symbol into position on the remaining reel, converting a near-miss into a full trigger.
The Second Chance is not guaranteed - it fires randomly, and you have no control over when it activates. But it softens the frustration of watching two Scatters land and the third miss by a single position. Over a long enough session, the Second Chance adds a small but meaningful number of extra feature triggers to the game.
RTP, Volatility and Where It Fits
At 96.4% RTP and low volatility, Boom Brothers is built for extended sessions rather than chasing a single big hit. The 20-payline structure keeps the maths simple, and the combination of Free Spins with Stacked Wilds and the separate Train Feature bonus gives the game two distinct paths to above-average wins.
The visual and audio design has inevitably aged since 2011, but NetEnt has kept the game available because the underlying mechanics remain solid. It occupies a niche in their catalogue as one of the few low-volatility games that includes both a genuine bonus round and a meaningful Free Spins feature.
For players who prefer steady sessions with occasional bonus interruptions rather than high-variance grind, Boom Brothers remains a functional choice. It will not compete with modern NetEnt releases on visual polish or maximum win potential, but the dual-feature structure gives it more variety than many slots of its vintage.
