Holosun Red Dot Sights: How to Decode the Model Numbers

HS507C-X2. HE507K-GR-X2-ACSS. HS407COMP-GD-6. Three real optics from the same Holosun range, and nothing in those names tells you the first is a red multi-reticle pistol sight, the second a green subcompact carrying a Primary Arms reticle, and the third a gold single-dot competition optic. The names are not arbitrary, though: they are a positional code, and once you can read it you can identify almost any Holosun optic before opening the listing.

Anatomy of a Holosun part number

Read left to right; most models fill only some positions.

The prefix tells you less than the suffix

The most repeated claim about Holosun naming is that HS means red and HE means green. Checked against what is on the shelf, it holds — but only where nothing contradicts it. The HS407C-X2, the HS507C-X2 and the HS510C are red; the HE507C-GR-X2 is green.

Now the exceptions. The HE508T-RD-X2 and HE509T-RD-X2 carry HE and are red. Going the other way, the HS407C-X3-GD and HS507COMP-GD are gold despite the HS. Holosun kept the old prefix while bolting an explicit colour code onto the end, and the two now disagree across a fair slice of the range.

The working rule: if the part number ends in a colour code, believe the colour code and ignore the prefix. Where there is no colour code, the prefix is your answer — HS red, HE green. It is also why the green and gold listings cannot be filtered on prefix alone.

Three part numbers, decoded end to end

HS507C-X2

HS — no colour code follows, so the prefix stands: red. 507 — Multi-Reticle System: a 2 MOA dot, a 32 MOA circle, or both as a circle-dot on a button press. C — the full-size open reflex body on the Trijicon RMR footprint, 16 × 23 mm window. X2 — second-generation optics. Drop 507 to 407 and you lose the circle and circle-dot, keeping a single 2 MOA dot in the same body.

HE507K-GR-X2-ACSS

HE suggests green and -GR confirms it. 507 would normally mean the Multi-Reticle System, but -ACSS overrides the reticle entirely: this one carries the Primary Arms ACSS Vulcan, a 10 MOA centre chevron inside a 250 MOA outer circle that can be switched off. You aim with the chevron tip, so it gives a finer aiming point than a 10 MOA dot while staying as easy to pick up. K is the subcompact body on the Holosun K footprint — a modified Shield RMSc pattern — with a 15 × 20 mm window. That is this optic; the other ACSS sights follow the same convention.

HS407COMP-GD-6

HS is overruled by -GD: gold, not red. 407 means a single fixed dot with no reticle menu. COMP is the competition body, a wider 28 × 22 mm window on the RMR footprint. -6 is the dot size in MOA. Add circles back and you have the HS507COMP, whose Competition Reticle System pairs a 2 MOA dot with selectable 8, 20 or 32 MOA circles. If choosing between a 2 and a 6 MOA dot is the sticking point, our MOA explainer covers what each hides at distance.

What the letter after the number changes

C, K, T and COMP are size and construction classes with real consequences for zeroing range and for what your rail or slide will accept. Figures below come from the store's manufacturer-verified data; unpublished figures are left out rather than estimated.

Two things worth pulling out. The K models halve their adjustment to ±30 MOA against the C models' ±50 MOA — the price of the smaller body, worth knowing before fitting one to a mount already off-axis. And T does not mean tactical; it means titanium. Both T-series optics use a Grade 5 titanium housing; the 508T is an open reflex with an exposed emitter while the 509T seals it inside, a trade-off our open reflex versus enclosed comparison sets out. Settle footprint compatibility first, via the footprints guide and the RMR and Holosun K listings.

The families that ignore the code entirely

• EPS and EPS Carry — fully enclosed pistol optics on the Holosun K footprint, running a side-loading CR1620 in a 7075 aluminium housing rated IPX8. The EPS is the full-size body with an RMR-to-K adapter plate; the EPS Carry is shorter, 15 × 20 mm window, RMSc-to-K plate. "Carry" is a size class describing a slim slide cut, not a use case. Suffixes read normally across the EPS range: RD-2 is a 2 MOA red dot, GR-6 a 6 MOA green, MRS the switchable set.
• AEMS — an enclosed rifle optic with a large square window, sub-named EVO, PRO X2, CORE X2, Macro, Micro or MAX rather than numbered. The AEMS EVO adjusts in 0.5 MOA clicks, ships with a four-post lower-1/3 co-witness mount, and uses a 65 MOA circle rather than the pistol optics' 32 MOA. Its housing is listed here as IPX8; Holosun's own material quotes IPX8 in some places and IP67 in others, so check with the manufacturer if the rating is decisive. More in the AEMS range.
• ARO — Advanced Rifle Optic, a compact enclosed micro with a 22 mm window and side-loading CR2032, aimed at shooters replacing an open tube dot. The ARO RD2 is the plain 2 MOA version; ARO MRS adds switchable reticles, ARO EVO enlarges the window. Click value and travel are not published, so neither appears here. See the ARO range.
• SCS — Solar Charging Sight, named after the pistol it bolts to rather than by series: SCS MOS for Glock MOS, then SCS 320, MP2, VP9, PDP, P10 and Carry. No adapter plate, and no replaceable cell — an internal rechargeable battery is topped up by the solar panel, roughly a 20,000-hour reserve, adjusting 1 MOA per click over ±30 MOA. The wrong suffix will not fit, hence SCS listings organised by pistol.
• HM3X, HM3XT, HM6X — flip-to-side magnifiers, not sights. The HM3X gives 3x with around 2.75 in of eye relief and a 7° field of view, IP67 aluminium; the HM3XT is lighter titanium, the HM6X steps to 6x.
• RONIN and ProMax — RONIN is a prefix marking a premium finish on an existing body, as on the RONIN AEMS MAX. ProMax is a large-window open reflex 507 running the Performance Reticle System: a 2 MOA dot with selectable circles.

Matching a family to what you shoot here

Airsoft

Airsoft guns are not firearms under the Firearms Act 1968. Section 57A, inserted by the Policing and Crime Act 2017, defines one as a barrelled weapon designed to discharge only a small plastic missile — spherical, made wholly or partly from plastics, no more than 8 mm across — and incapable of exceeding the permitted muzzle energy: 1.3 joules for a weapon firing two or more missiles successively without repeated trigger pressure, 2.5 joules otherwise. With no meaningful recoil to survive, housing material and IP rating matter far less than window size and speed of acquisition. The 65 MOA circle on a 510C or an AEMS is the quickest thing here to pick up at skirmish distances.

Sub-12 ft lb air rifles

Home Office guidance sets the thresholds at 12 ft lb for an air rifle and 6 ft lb for an air pistol (s.2.46); above those an air weapon is not an exempt air weapon. Scotland differs: section 2 of the Air Weapons and Licensing (Scotland) Act 2015 makes it an offence to use, possess, purchase or acquire an air weapon there without an air weapon certificate issued by Police Scotland (s.2.52). Northern Ireland has its own firearms legislation entirely (s.4.5). Confirm your position with your police firearms licensing department.

The 0.5 MOA clicks on the 510C are the finest adjustment in the range and suit what an air rifle can do at 25 to 40 yards (23 to 37 m). One thing to plan for: many UK air rifles carry an 11 mm dovetail rather than a Picatinny rail, and every Holosun mount here is Picatinny or a pistol footprint. A dovetail-to-Picatinny adapter is an airgun-trade item rather than part of an optics range, so source it from an airgun dealer alongside the sight.

Practical and competition pistol

Pistol shooting in Great Britain means long-barrelled revolvers and pistols held on a firearm certificate, air pistols and airsoft pistols. Long-barrelled pistols and revolvers may be held on a firearm certificate where their dimensions exceed those stipulated in section 5(1)(aba) of the Firearms Act 1968 — your licensing department is the authority on your own application, and Northern Ireland has its own firearms legislation (Guide on firearms licensing law, s.4.5). The COMP bodies exist for this: the widest window in the pistol range, and selectable 8, 20 and 32 MOA circles on the HS507COMP to tune the sight picture to the stage. If you would rather have nothing to press, the HS407COMP is the fixed 6 MOA version.

Certificate-held rifles and stalking

For a certificate-held rifle at closer ranges, the T-series is where construction gets serious: Grade 5 titanium, open in the HE508T-RD-X2, sealed in the HE509T-RD-X2. On a rail, the HS510C arrives with its quick-detach lower-1/3 mount fitted; put an HM3X behind it for 3x on demand without giving up the 1x picture. Be clear-eyed about the limit: a 1x dot with a 3x magnifier is no substitute for a riflescope when stalking at range, and a specialist range built around red dots, holographic sights and magnifiers carries no variable-power scopes — that is a purchase for a general rifle dealer. Whichever you fit, zero it properly first.

The short version of the code

The number tells you the reticle, the letter tells you the body and footprint, the X-number tells you the generation, and the colour code at the end overrules the prefix at the front. Everything after that is finish — the only part you are free to choose on looks.