A conventional speargun pushes the shaft with bands stretched from the muzzle, a railgun is a conventional band gun with a rail that guides the shaft along the full barrel, and a rollergun routes the bands around muzzle rollers to give a much longer power stroke from the same length. Railguns are the accurate, simple all-rounders; rollerguns give more power and range with less recoil but are more complex to rig and load.
Key takeaways
- Conventional and railguns are simpler, easier to load and easier to maintain.
- The rail supports the shaft along the barrel, which helps accuracy and keeps the shaft aligned.
- Rollerguns give a longer power stroke, more range for their length and low recoil.
- Rollers add parts to maintain: bearings, band anchors and a more involved loading routine.
- Beginners usually start with a conventional gun or railgun; experienced divers often add a rollergun for open water.
How a conventional band speargun works
In a conventional speargun, rubber bands are fixed at the muzzle. When you load the gun you stretch the bands back and hook their wishbones into notches or fins on the shaft. Pulling the trigger releases the shaft and the bands accelerate it forward until they reach their resting length at the muzzle.
The design is simple, robust and easy to service. The Rob Allen Scorpia Speargun and the Rob Allen Cobia Speargun are good examples: aluminium barrels, a single 16 mm band and a glass-reinforced nylon mechanism, in short lengths for reef and shore diving. The Rob Allen Havoc Timberline Speargun applies the same principle at a more powerful level, with a carbon barrel in a mahogany body, three 14 mm bands and an 8 mm shaft.
What is a railgun?
A railgun is a conventional band gun whose barrel has an integrated rail along the top. The shaft sits in this rail and is supported for its full length. That support keeps the shaft straight while it accelerates, reduces flex and sideways movement, and tends to make the gun quieter because the shaft is not slapping against a round barrel.
Most modern band guns, including many in our conventional guns category, are railguns. Examples include:
- Rob Allen Caranx Railgun 1200 Speargun: aluminium barrel with a full-length extruded rail, 7 mm single-notch shaft, fitted with one 20 mm band and able to take two.
- Rob Allen Tuna Railgun Speargun: aluminium railgun with an open muzzle, double 16 mm bands and a 7.5 mm double-notch spear, offered from 60 to 140 cm.
- Rob Allen GT Carbon Railgun Speargun Camouflage: pullwound carbon barrel with integrated guide rail, twin 16 mm bands and a 7.5 mm tri-cut spear.
- Rob Allen BlueFin Pro Speargun: carbon railgun with a Vecta triple muzzle, three 14 mm bands and a 7.5 mm triple-fin shaft for bluewater hunting.
How a rollergun works
In a rollergun the bands are not fixed at the muzzle. Instead they are anchored under the barrel near the handle, run forward, pass around rollers in the muzzle and come back over the top to the shaft. When the gun fires, the bands pull the shaft all the way from the loading position to the muzzle, so the power stroke is roughly twice as long as on a conventional gun of the same length.
Because the bands pull from both ends of the barrel, forces are more balanced, which is why rollerguns are known for low recoil and good accuracy for their power. The cost is complexity: more parts, bearings that must turn freely, and a loading routine that takes practice.
Rollerguns currently in our rollergun category include:
- Rob Allen Tuna Roller Speargun: aluminium rail barrel, roller muzzle with four ceramic bearings, 16 mm bands and a 7.5 mm notched shaft, 80–120 cm.
- Rob Allen GT Carbon Roller Speargun: carbon barrel built on a Tuna roller layout, four ceramic bearings, 90–140 cm.
- Rob Allen Timberline Roller Speargun: hand-built carbon hybrid barrel with a mahogany oversleeve, ceramic nitride bearings and a low-profile reel, 90–120 cm.
Rob Allen also offers a Double Roller Speargun Muzzle that converts a compatible Rob Allen rollergun into a double rollergun for a longer power stroke. New double rollerguns such as the BlueFin Double Rollergun and Chaos Timberline Double Rollergun are listed as pre-order items.
Railgun vs rollergun vs conventional: comparison table
| Feature | Conventional (round barrel) | Railgun | Rollergun |
|---|---|---|---|
| Power for barrel length | Standard | Standard | Higher (longer power stroke) |
| Shaft support | Shaft rests on barrel | Supported along full rail | Usually supported by a rail |
| Recoil | Moderate | Moderate | Low for its power |
| Loading | Easiest | Easy | Harder, needs practice |
| Maintenance | Minimal | Minimal | More parts: rollers, bearings, anchors |
| Noise | Can be noisier | Quiet | Quiet if well rigged |
| Best for | Simple reef and shore guns | Most conditions, all-rounder | Open water, longer shots, big fish |
| Skill level | Beginner | Beginner to expert | Intermediate to expert |
Pros and cons in detail
Conventional and railguns
- Pros: simple to load and rig, few moving parts, reliable, easy to service on a trip.
- Pros: adding power is straightforward: add a band or use thicker rubber, if the barrel supports it.
- Cons: for a given range you need a longer barrel than a rollergun.
- Cons: heavy multi-band setups increase recoil and can make the gun jump on the shot.
Rollerguns
- Pros: more range from a shorter, more manoeuvrable barrel.
- Pros: low recoil and stable shots.
- Cons: more complex rigging and loading; bands are long and need correct sizing.
- Cons: rollers and bearings must be rinsed and checked after every dive.
Which Rob Allen gun fits which use?
| Use | Suggested type | Rob Allen examples |
|---|---|---|
| Holes, caves, low visibility | Short conventional gun | Scorpia, Cobia |
| General reef and shore | Railgun 70–100 cm | Caranx Railgun, Tuna Railgun |
| Clear coastal water | Railgun 100–120 cm | Tuna Railgun, GT Carbon Railgun |
| Bluewater and pelagics | Multi-band railgun or rollergun | BlueFin Pro, Havoc Timberline, GT Carbon Roller |
| Maximum range in a compact gun | Rollergun | Tuna Roller, Timberline Roller |
If you are unsure about length as well as type, see our guide on how to choose a speargun length. You can also compare everything in our full speargun range.
Should a beginner buy a rollergun?
Most beginners are better served by a railgun. It teaches good aiming and loading habits, is easier to maintain and is more forgiving if something goes wrong. Once you are comfortable and regularly hunt in clear water, a rollergun is a logical next step.
FAQ
Is a railgun more accurate than a conventional gun?
The rail supports the shaft along the whole barrel, which keeps it aligned and reduces flex during the shot. Many divers find railguns more accurate and quieter than round-barrel guns of the same length.
Do rollerguns shoot further?
Yes, for the same barrel length. The bands travel around the muzzle rollers, giving a longer power stroke. For the Tuna Roller, Rob Allen states an effective range of approximately six times the barrel length from the muzzle tip.
Are rollerguns hard to load?
They take more practice than a railgun because the bands are longer and you load them in stages. A loading aid can help with heavy bands.
Can I convert my speargun to a rollergun?
Some Rob Allen rollerguns can be converted to a double rollergun with the Rob Allen Double Roller Speargun Muzzle. Compatibility depends on the model, so contact us with your gun model and length before ordering.
Are railguns conventional guns?
Yes. A railgun is a type of conventional band speargun whose barrel has an integrated rail. That is why railguns appear in our conventional guns category.