Squared barbs: 15% faster, 30% stronger — Rob Allen’s 2025 update

The single biggest Rob Allen product change in 2025 was the squared barb. Most spearos have not caught up with what it does yet. Here is the actual engineering case, pulled from Rob’s own test station footage.

What changed

Traditional spear barbs are radiused — the pivoting barb is roughly half-round in cross-section, pivoting out from a matching radiused slot cut in the shaft.

The 2025 squared barb is half-square in cross-section, pivoting out from three machined flat sides cut into the shaft. Same barb length, same barb mechanism, just a different geometry for the metal-in-metal interface.

Rob: “My theory is that a piece of half square channel is gonna be way stronger than a half round. The proof on the pudding is in the tasting.”

So he tested it. Twice. Part 1 and Part 2.

The speed gain

Rob’s initial pool testing: approximately 15% more spear velocity on the same gun with a squared barb vs a radiused barb.

Why: the three-faceted squared barb is recessed deeper into the shaft than a radiused barb can be. This lowers the drag coefficient as the spear leaves the gun. Less drag = more velocity retained through the shot.

And because spear velocity is directly proportional to penetration, 15% more velocity = 15% more penetration at the same range. On a marginal shot on a tough-fleshed bluewater fish, that can be the difference between a stone kill and a runner.

The strength gain

Rob’s break test: the squared-barb geometry failed at roughly 30% higher load than the radiused-barb equivalent.

Why: half-square channel has more material at the high-stress points than half-round. The barb is physically harder to bend or break against a fish thrashing in structure.

Real-world application: a grouper running into a cave with your spear through it, or a big GT thrashing in coral. Radiused barbs can bend out. Squared barbs resist more of that load before failing.

How much shaft is removed for a squared-barb slot?

Rob addressed this directly in Part 2 because guys were asking:

• The slot is cut on three sides of the shaft (the three sides the muzzle cuts into on loading), not all four.
• Depth: just over half a millimetre past the circumference — enough for barb clearance, not enough to weaken the shaft.
• For shark-tagging applications on 7 mm shafts, Rob has cut more than 50% of the shaft away and the shaft still holds. So the squared-barb cut depth is safely within the shaft’s load tolerance.

Translation: you do not lose any meaningful shaft strength from the new geometry.

Availability

Squared barbs are being rolled out on Rob Allen 7.5 mm and 8 mm spears. The 7 mm line retains the older radiused design for now (mostly used for shark-tagging rigs and specialist applications).

If you are ordering new spears from me, the Rob Allen factory is shipping squared-barb 7.5/8 mm as standard on 2025+ production. Old-stock radiused-barb spears are still being cleared through the supply chain, so if you specifically want the squared design, ask me before you order and I will check the current batch.

Who should upgrade now

• Bluewater spearos chasing wahoo, dogtooth, big Spanish mackerel, GT over 15 kg. The 15% penetration gain matters most on tough-fleshed large fish at the margins of your gun’s effective range.
• Hole-hunters going after big grouper in structure. The 30% barb strength gain matters when a fish goes into a coral cave and thrashes hard against the barb.
• Anyone replacing worn 7.5 or 8 mm spears anyway. The new geometry is the same price as the old. No reason not to.

Who does not need to upgrade

• Reef spearos under 10 kg fish targets. The barb strength gain does not come into play. The velocity gain is marginal at close range. If your current spears are still good, keep using them.
• 7 mm shafts users. Not available yet.
• Anyone who just bought new radiused-barb spears. They are perfectly fine — the radiused design worked for 30+ years of Rob Allen production. Use them until they wear, then upgrade.

How to tell what you own

Look at the spear next to the barb. Pivot the barb out and check the slot:

• Rounded cross-section to the slot = radiused barb (older design)
• Squared cross-section with three flat faces = squared barb (2025+)

If you are unsure, send me a photo on WhatsApp and I can tell you in five seconds.

Full range

The rubbers and shafts category has every current Rob Allen spear in stock. I’m working through the inventory to label which batches are squared-barb vs radiused — if you want to reserve squared-barb specifically, message me before ordering.

The Part 1 break test video is here. The Part 2 follow-up with design refinements is here.