• Airsoft Helden HR556 10 inch S-HPA mechanical HPA airsoft rifle in black
  • Airsoft Helden HR556 showing MechLabs XX-Mod mechanical HPA engine
  • Airsoft Helden HR556 aluminium M-LOK handguard and 20mm flat-top rail
  • Airsoft Helden HR556 with 190 round mid-cap magazine
  • Airsoft Helden HR556 with folding stock
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Airsoft Helden HR556 10in S-HPA — Mechanical HPA Rifle, Black

Airsoft Helden HR556 10in S-HPA — Mechanical HPA Rifle, Black

£599.95
£599.95
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DETAILS

SKU: 8502185155
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📖 New to HPA? This runs on external high pressure air — it needs a tank, a regulator and a line before it will fire a shot. Read our complete HPA guide before buying.
No electronics, and no hop rubber either. The HR556 runs a fully mechanical MechLabs XX-Mod engine behind a ROTO chamber that does away with the bucking altogether — two of the three things that usually fail on an HPA build simply are not in it.

Most HPA guns answer to a circuit board. This one does not have one. The XX-Mod is mechanical from trigger to nozzle, which MechLabs take far enough to rate the engine fully waterproof and say it keeps cycling while submerged. Nothing to pair, nothing to charge, nothing to go down in the rain.

The hop-up is the other unusual part. A ROTO chamber has no hop rubber in it. Instead a machined contact pad is built into the chamber itself and applies the backspin directly, which takes the single most common consumable on any airsoft gun out of the equation along with the way it goes off over a season.

Behind that sits a 292mm 6.03mm tightbore and an output that adjusts up to around 2.3 joules, with Airsoft Helden recommending 0.36g BBs. That is a heavy BB and a high ceiling, so this is a rifle set up to reach rather than to spray — dial it down for CQB and it will happily sit at a site limit instead.

What you need to run it

Item Notes
HPA tank Not included — see HPA tanks
Regulator Required — see HPA regulators. Set velocity on the regulator and chrono it
Air line Not included — see HPA lines
Battery None. The engine has no electronics in it at all
Magazines Airsoft Helden list a PTS EPM1-S 170rd and their own 195rd midcap as fitting — see AEG magazines
Hop rubber None needed. The ROTO chamber runs without a bucking

Specifications

Specification Detail
Engine MechLabs XX-Mod, a fully mechanical HPA engine for V2 gearboxes
Electronics None. No board, no wiring, no sensors
Weather sealing MechLabs rate the engine 100% waterproof and say it keeps working fully submerged
Hop-up MechLabs ROTO chamber, buckingless — an integrated contact pad in place of a hop rubber
Inner barrel 292mm, 6.03mm tightbore
Output energy Adjustable, up to approximately 2.30 joules
Fire modes Semi and full auto
Rate of fire Tunable through the engine’s Air Bender adjustment
Engine construction CNC-milled Series 6 aluminium, modular block design with a lock-fit interface
Receiver fit 3-axis XYZ alignment on the engine for air-path precision
Rails M-LOK and Picatinny
Recommended BB 0.36g
Colour Black

Good to know

The XX-Mod is a drop-in replacement for a standard V2 AEG gearbox, so the engine itself is a known quantity with its own spares and upgrade path rather than something proprietary to this rifle. The Air Bender adjustment on it trims the internal air cycle, which is how you trade rate of fire against shots per bottle.

Frequently asked questions

Is there really no hop rubber? Correct. The ROTO chamber uses an integrated contact pad instead, so there is no bucking to replace and nothing to go hard or tear.

Does it need a battery? No. The engine is entirely mechanical, so there is no board, no wiring and nothing to charge between games.

What pressure should I run it at? Set your velocity on the regulator and confirm it over a chrono. Start low and come up.

Will it survive a wet day? MechLabs rate the engine as fully waterproof and state it works even submerged. That claim is theirs and it is about the engine, not the optics or the magazine.

Which magazines fit? Airsoft Helden list the PTS EPM1-S 170-round and their own 195-round midcap against this rifle.

⚠ Always run a secondary regulator. Never put tank pressure straight into the engine. Set your output before you shoot, and chrono at the site every time.
⚠ UKARA: As a realistic imitation firearm, this product requires UKARA registration or a valid defence. We verify at checkout. Register by playing 3 games over 56+ days at Skirmish Wycombe Airsoft.
💡 Titan Forge Airsoft tip: A mechanical engine is the easy one to live with, but it still wants clean regulated air — pair it with a regulator you trust rather than the cheapest one. We can set it to your site limit before it ships through the HPA tech service.