How to read an airsoft gun spec sheet

Bottom line

Manufacturer spec sheets are written by marketing departments. The numbers that matter — for whether the gun is good, upgradable, and compatible with the parts you'll want — are usually buried, missing, or quoted misleadingly. Here's what to look for and what to ignore.

The numbers that actually matter

FPS — and what BB weight it was measured with

What's listed: "350 FPS" or "1.13J"

What to ask: At what BB weight? With what hop setting? With what spring? With what nozzle / cylinder combo?

A "350 FPS" gun could mean:

• 350 FPS at 0.20g with hop off (the marketing number) — actually 1.13J
• 350 FPS at 0.25g with hop set for level shot (still around 1.4J — would fail chrono at most sites with that BB)

The number to trust: joules. If the spec sheet quotes 1.13J without weight specification, that's the energy regardless of weight — chrono-relevant.

Marketing trick to watch: "Up to 400 FPS!" usually means a single peak reading at 0.20g with a brand-new spring, not the average you'll get after the first 500 rounds when the spring settles.

Real-steel equivalent / platform

What's listed: "M4 platform", "AK-74 pattern", "MP5K"

Why it matters more than you'd think:

• Magazine compatibility: an M4 platform takes STANAG-compatible mags from a dozen brands. A proprietary platform (think PTW, AAP-01) only takes its own mags.
• Aftermarket parts: M4, AK, MP5, G3, AR-15 family all have huge aftermarket parts catalogues. A niche platform (FN P90, FAMAS, AUG) means you're paying premium for any spare.
• Rail systems: M-LOK, KeyMod, picatinny — affects what accessories bolt on.
• Holster fit (for pistols): Glock-pattern, 1911-pattern, SIG P226, P320 — determines which holsters you can use.

Marketing trick to watch: "Tactical M4" with no actual M4 internals (proprietary gearbox). Check the gearbox version.

Gearbox version (AEG only)

What's listed: "V2 gearbox", "V3 gearbox", "V6 gearbox", "V7 gearbox", "split gearbox", "QSC"

The version determines:

• Compatibility with upgrade parts (motors, gears, pistons, MOSFETs, ETUs)
• Disassembly difficulty — V2 needs full removal of the gun's lower receiver to open; some V3s split in half
• Trigger response — V2s tend to have shorter trigger pulls; V3s are longer but more durable

Standard versions by platform:

• M4 family → V2
• AK family → V3
• MP5 family → V2 or V3 (varies)
• AUG / G36 → V3 or V7
• L85 / SA80 → V7

Specialty versions:

• ICS Split Gearbox → V2 / V3 that splits without full disassembly (massive QoL win for tech work)
• Tokyo Marui Recoil Shock → V2 but with proprietary recoil mechanism

Marketing trick to watch: "Reinforced gearbox" with no version number. Could be anything. Don't pay extra without specifics.

Hop unit

What's listed: "Rotary hop", "Lever hop", "Maple Leaf hop", "Brand-specific hop"

The hop unit controls backspin on the BB and is the single most important factor in accuracy and range:

• Rotary hop (most modern AEGs) — dial-adjustable, holds setting, easy to fine-tune
• Lever hop (older designs, some AK clones) — pivots in/out, less precise, drifts over time
• Maple Leaf / brand aftermarket hops — premium drop-in replacements, often the first upgrade tech players make

Marketing trick to watch: "CNC hop unit" — could be poorly designed CNC. The brand matters more than the manufacturing method.

Inner barrel length & diameter

What's listed: "364mm inner barrel", "6.03mm tight bore"

What matters:

• Length correlates loosely with FPS efficiency. Longer barrel = more time for air to push the BB. A short-barrelled AEG can be upgraded to hit the same FPS with a heavier spring; an over-long barrel hurts efficiency.
• Bore diameter:
  • 6.08mm (loose bore) — Tokyo Marui spec. Forgiving of dirty hop / cheap BBs. Best for stock guns.
  • 6.05mm — middle ground
  • 6.03mm (tight bore) — accuracy-focused, requires clean hop and quality BBs
  • 6.01mm — competition tight bore, demanding

Marketing trick to watch: tight bore as a "premium feature" on a stock gun — actually causes more problems than it solves at stock FPS.

Motor

What's listed: "Long type motor", "Short type motor", "high torque / high speed"

The motor's torque and RPM determine trigger response and battery efficiency:

• High torque — slower spin, more pull power. Use with upgraded heavy springs (M120+). Good for woodland / DMR.
• High speed — faster spin, less pull. Use with stock or light springs (M100 and under). Good for CQB / speedsoft.
• Balanced — middle ground, factory default in most stock guns.

Brand matters: SHS, Lonex, ASG (Ultimate), Tokyo Marui EG-1000 — these are the recognised quality brands. No-name motors are usually the first upgrade.

Battery connector

What's listed: "Tamiya connector", "Deans/T-plug", "XT60", "JST"

• Tamiya — factory default on most stock AEGs, terrible current handling, first thing tech players replace.
• Deans (T-plug) — better current handling, low profile.
• XT60 — best for high-current applications.

Marketing trick to watch: spec sheet not mentioning the connector at all. Default to assume Tamiya, plan to upgrade.

Mag capacity & type

What's listed: "300rd hi-cap", "120rd mid-cap", "30rd real-cap"

• Hi-cap — wound spring inside the mag, capacity 200–600 BBs, rattles when you move, cheap (£8–15).
• Mid-cap — spring-fed, 80–150 BBs, silent, more realistic reloads, slightly more expensive (£12–20).
• Low-cap — 30–80 BBs, more realistic, niche.
• Real-cap — actual round count of the platform (30 for M4, 20 for G3, etc.), expensive, used by milsim impression players.

Marketing trick to watch: "1 magazine included" with no specification. Often a hi-cap; many starter guns ship with no mid-caps at all.

Weight & length

Useful for:

• Holsters and slings that need to fit
• CQB / speedsoft where every gram matters
• Build aesthetics — featherweight polymer guns feel like toys; metal-receiver guns feel like the real thing

Marketing trick to watch: weight quoted without battery. Add 100–200g for a typical battery in the stock or handguard.

The numbers nobody quotes but you should ask about

Air seal / cylinder volume

Determines how efficiently the gun converts spring energy to BB velocity. Tech-heavy reviewers (UKARA, Negative Airsoft, Novritsch's tech videos) often cover this. Manufacturer spec sheets never do.

Trigger pull (in ms)

Modern AEGs with ETU / MOSFET should hit sub-30ms lock time. Stock AEGs without active electronics: 60–80ms. HPA: 8–15ms. GBB: 5–10ms.

Out-of-the-box accuracy

What grouping does it shoot at 30m with stock hop and stock BBs? Manufacturer spec sheets never quote this. Player reviews on the catalogue do.

MOSFET / ETU fitted from factory?

ETU (Electronic Trigger Unit) gives you burst fire, programmable trigger response, low-voltage cutoff for LiPo safety. Many premium AEGs ship with ETUs; budget ones don't. This is worth £40+ in upgrade cost if you'd add one anyway.

Red flags on a spec sheet

• "FPS 350-400" with a 50 FPS range — quality control is poor, every gun will be different
• No gearbox version listed
• "Made of high-grade polymer" — means plastic, possibly low-grade
• "Realistic recoil!" on an AEG — usually a small reciprocating dummy bolt, fun but adds nothing performance-wise
• No reference to compatibility with major aftermarket parts — proprietary platform

Green flags

• Spec sheet quotes joules + BB weight
• Gearbox version explicit, with motor type
• MOSFET or ETU listed
• "Compatible with [platform] aftermarket parts" explicitly
• Real-steel equivalent referenced
• Mid-caps included (not just hi-caps)

What to do with this

Before you buy a gun:

1. Find the catalogue page on airsoftcatalog.com — we list the spec fields manufacturers don't always emphasise.
2. Check the gearbox version — make sure aftermarket parts you want exist for it.
3. Note the FPS in joules, not just FPS — and confirm it matches your local site's limits.
4. Check what magazines it takes — STANAG / proprietary / brand-specific.
5. Search for a tear-down video on YouTube before committing — Novritsch, Negative Airsoft, AirsoftGI all do thorough internal reviews.

Sources & next steps

• AEG vs GBB vs HPA — platform decision guide
• BB weights explained — why "FPS" is meaningless without weight
• FPS, joules and chronos — how site limits actually work
• Browse the gun catalogue →