STEN Gun · Volume 12
Cheatsheet
Laminate-ready synthesis — dim sheet, legal pivots, vendor reference, bibliography
Contents
(Generated by build/inject_toc.py at build time. Section headers below are the source of truth.)
This laminate-ready synthesis compresses the deep dive into one document to print, laminate, and keep with the gun — covering the dimensional reference, the legal pivots, the vendor contacts, and the bibliography. Everything here is drawn from Vols 1–11; for the why behind any entry, read the originating volume.
The volume is organized for quick lookup: dimensional reference (§ 12.2), the three build paths at-a-glance (§ 12.3), the legal-posture quick map (§ 12.4), the failure-mode quick table (§ 12.5), the magazine and ammunition quick reference (§ 12.6), vendor contacts (§ 12.7), and the canonical bibliography (§ 12.8).
12.1 The STEN at a glance
Table 1 — 12.1 The STEN at a glance
| Fact | Value |
|---|---|
| Type | Submachine gun, open-bolt blowback (orig.); closed-bolt semi-auto (new US builds) |
| Caliber | 9×19 mm Parabellum |
| Designers | Major Reginald V. Shepherd + Harold J. Turpin (RSAF Enfield, 1941) |
| Manufacturers | RSAF Enfield, BSA, ROF Fazakerley, ROF Theale, Lines Brothers Tunbridge, Long Branch (Canada), Lithgow (Australia) |
| Production | ~4–4.5 million units, 1941–1953 |
| Marks in scope | Mk I, Mk II (canonical), Mk III, Mk IV (rare), Mk V (wood furniture), Mk VI (suppressed) |
| Wartime cost | ~£2.50 per unit at Fazakerley peak (1944) |
| Wartime labor | ~10 man-hours per unit at peak |
| Cyclic rate (full-auto) | ~550 rpm |
| Practical range | 100 m point-target; 200 m area-suppression |
12.2 Dimensional reference — Mk II canonical build
Drawn from Vol 4 § 4.2. All values nominal Mk II; verify against UK MoS drawing or Professor Parabellum Vol III before cutting metal.
Table 2 — 12.2 Dimensional reference — Mk II canonical build
| Spec | Value | Notes |
|---|---|---|
| Caliber | 9×19 Parabellum | Factory; SAAMI modern chamber works |
| Overall length, stock attached | 762 mm (30.0″) | With skeleton T-stock |
| Overall length, stock detached | 553 mm (21.8″) | Stocks are detachable |
| Barrel length | 197 mm (7.75″) | SBR by US federal definition |
| Weight, empty + stock | 3.18 kg (7.0 lb) | |
| Weight, loaded (32-rd mag) | ~3.65 kg (8.05 lb) | |
| Receiver tube OD | ~38 mm (1.50″) | Rolled-and-welded 1.5 mm CR steel |
| Receiver tube ID | ~35 mm | Sliding fit on bolt |
| Receiver tube length | ~533 mm | Full tube buttplate-to-muzzle |
| Receiver tube wall | 1.5 mm (0.060″) | 1018 CR sheet |
| Bolt OD (sliding fit) | ~32 mm ± 0.05 | Sliding fit in receiver ID |
| Bolt length | ~210 mm | |
| Bolt mass | ~590 g | Drives blowback timing |
| Recoil spring free length | ~280 mm | Compresses to ~145 mm |
| Recoil spring wire | ASTM A228 music wire, ~2 mm dia | |
| Magazine capacity | 32 rounds | Single-feed Lanchester-derived |
| Trigger pull | ~2.5–3.5 kg | Varies |
| Sights | Fixed front blade + flip-aperture rear (Mk II); Lee-Enfield No 4 (Mk V) | 100 yd zero typical |
| Stock | Skeleton T-frame, 9.5 mm 1018 steel rod (Mk II) |
12.2.1 Material substitution quick reference
Table 3 — 12.2.1 Material substitution quick reference
| WWII spec | Modern US-available equivalent |
|---|---|
| Mild steel sheet (receiver) | 1018 cold-rolled, 0.060″ thick |
| Plain carbon steel (bolt) | 4140 alloy, case-hardened bolt face |
| Stamped sheet (FCG housing) | 1018 sheet, 16-gauge; OR 6061-T6 for CNC alternative |
| Music wire (springs) | ASTM A228, various dia |
| Steel rod (skeleton T-stock) | 1018 round bar, 9.5 mm |
| Hardwood (Mk V furniture) | American walnut preferred; birch acceptable |
| Pre-rifled barrel blank | 4150 chrome-moly 9×19 from E.R. Shaw, Green Mountain, McGowen ($80–150) |
12.3 The three build paths at a glance
12.3.1 Path A — NFA Class III pre-86 transferable (Vol 5)
Table 4 — 12.3.1 Path A — NFA Class III pre-86 transferable (Vol 5)
| Aspect | Value |
|---|---|
| Result | Federally-registered machine gun, full-auto capable |
| Cost | $10K–25K (gun) + $200 stamp + $200–500 attorney/trust + dealer fees |
| Time | 6–14 months Form 4 approval |
| Operation | Open-bolt original WWII configuration; no rework needed |
| 922(r) | Does not apply (NFA machine guns are exempt) |
| 1982 closed-bolt | Does not apply (registered MG is exempt) |
| State | Most states permissive; NY/NJ/IL-Cook/RI/HI prohibited |
| Lifetime | Form 5320.20 for interstate transport; Form 5 estate transfer; constructive-possession storage |
| Best for | Builder who wants authenticity + select-fire and can absorb the cost |
12.3.2 Path B — Parts kit + US semi-auto receiver + 922(r) (Vol 6)
Table 5 — 12.3.2 Path B — Parts kit + US semi-auto receiver + 922(r) (Vol 6)
| Aspect | Value |
|---|---|
| Result | Closed-bolt semi-auto carbine on US receiver; 922(r)-compliant |
| Cost | $400–1,200 total ($200–500 kit + $30–400 receiver + $200 SBR stamp + parts + finishing) |
| Time | 15–30 hours bench work + 6–10 months Form 1 SBR approval |
| Operation | Closed-bolt FCG rework required (Vol 7 § 7.5 template) |
| 922(r) | Applies; canonical 4-replacement package (stock + magazine body + follower + floorplate) |
| 1982 closed-bolt | Applies; FCG must be reworked closed-bolt |
| State | Most states permissive; SBR posture (or ≥16″ barrel); AW restrictions in CA/NY/NJ/WA |
| Best for | Most builders — the iconic US “buy a kit and build” SMG project |
12.3.3 Path C — From scratch in 9×19 lab build (Vol 7)
Table 6 — 12.3.3 Path C — From scratch in 9×19 lab build (Vol 7)
| Aspect | Value |
|---|---|
| Result | Closed-bolt semi-auto carbine fabricated entirely in the lab |
| Cost | $300–800 materials + $200 SBR stamp + $40–60 headspace gauges |
| Time | 40–80 hours first build; 25–40 hours subsequent builds; 6–10 months Form 1 SBR approval |
| Operation | Closed-bolt FCG required from new build (Vol 7 § 7.5) |
| 922(r) | Does not apply (no imported parts) |
| 1982 closed-bolt | Applies; FCG built closed-bolt from start |
| State | Some states require state-level serialization (CA, NY, NJ, WA, others) |
| Lab requirements | CNC mill ≥250 mm travels, lathe ≥250 mm BC, sheet-metal roller, TIG welder, 9×19 chamber reamer + headspace gauges |
| Best for | Builder with full lab capability who wants the centerpiece project; a well-equipped home lab is over-capable for this build |
12.4 Legal-posture quick map
12.4.1 Federal pivots
Table 7 — 12.4.1 Federal pivots
| Pivot | Rule | Action |
|---|---|---|
| Machine gun = NFA + § 922(o) | Full-auto = NFA, post-86 manufacture/transfer prohibited | Path A only for full-auto |
| 1982 closed-bolt rule (ATF 80-21) | New semi-auto SMGs must be closed-bolt | Path B/C requires closed-bolt FCG rework |
| 18 USC § 922(r) + 27 CFR § 478.39 | ≤10 of 20 listed parts may be imported in semi-auto SMG built from imported parts | Path B requires the count arithmetic; canonical 4-replacement |
| SBR (NFA) | Rifle barrel <16″ or OAL <26″ → SBR | Path B/C: Form 1 + $200 stamp, OR extend barrel ≥16″ |
| Manufacture-for-personal-use | Federal exemption from FFL requirement for personal-use builds | Path C lawful in permissive states |
| 2022 Frame & Receiver Rule (27 CFR § 478.12) | Expanded definition of “firearm” | 80% receiver path narrowed but still viable for Sten |
| Constructive possession | Combination of parts that could be assembled into NFA item | Destroy/dispose original open-bolt parts after Path B rework |
12.4.2 State-by-state quick map
Table 8 — 12.4.2 State-by-state quick map
| Posture | Example states | Path viability |
|---|---|---|
| Permissive | TX, FL, AZ, NV, GA, NC, SC, TN, OH, PA, KS, OK, AL, MS, MO, IN, KY, etc. | All three paths viable |
| Permissive + state licensing | CT, MA | All three paths with state license |
| Restrictive (AW + SBR) | CA, WA, CO, MD | Limited path viability; consult state attorney |
| Prohibited / substantially prohibited | NY, NJ, HI, RI, IL (Cook), DC | None viable for private builders |
12.5 Failure-mode quick table
From Vol 11 § 11.5. Severity codes: 🔴 HIGH (stop firing), 🟡 MEDIUM (inspect), 🟢 LOW (clear and continue).
Table 9 — 12.5 Failure-mode quick table
| Failure | Severity | Most-common cause | Quick fix |
|---|---|---|---|
| Out-of-battery fire | 🔴 | Closed-bolt striker over-travel | Adjust striker; verify firing-pin protrusion |
| Light primer strikes | 🟢 | Firing-pin spring weak | Replace spring; try fresh ammo |
| Stovepiped case | 🟢 | Extractor weak | Replace extractor |
| Failure to feed | 🟢 | Magazine feed-lip pathology | Replace magazine (fresh aftermarket) |
| Failure to extract | 🟡 | Chamber fouling or worn extractor | Clean chamber; replace extractor |
| FCG fails to reset | 🟢 | Disconnector spring weak | Replace disconnector spring |
| Magazine catch fails | 🟢 | Wrong catch for magazine pattern | Install Bear Arms US-made catch for Sterling mags |
| Headspace shifts (NO-GO closes) | 🔴 | Chamber/bolt wear | Stop firing; have gun inspected |
| Closed-bolt slam-fire (double tap) | 🔴 | Striker latch failure | Stop firing; consult attorney; repair before resumption |
12.6 Magazine and ammunition quick reference
12.6.1 Magazines
Table 10 — 12.6.1 Magazines
| Pick | Vendor | Cost | Notes |
|---|---|---|---|
| CANONICAL | Bear Arms Sterling-pattern 32-rd | $25–35 each | US-made; counts as 922(r) US replacement |
| Alternate | ASP Sterling-pattern 32-rd | $25–35 each | Comparable to Bear Arms |
| Alternate | GunSpring Sten/Sterling | $25–35 each | Stronger spring for full-auto Sterling use |
| Surplus | Used Sterling Mk 4 / L2A3 mags | $20–45 each | Post-war UK production; mature feed-lip geometry |
| Collector only | WWII original Sten magazines | $15–40 each | Feed-lip pathology; do not rely on for shooting |
Recommended quantity: 4 magazines minimum for normal range use.
12.6.2 Ammunition
Table 11 — 12.6.2 Ammunition
| Pick | Use case | Cost (per 50) |
|---|---|---|
| CANONICAL | 9×19 NATO ball, 124-gr FMJ (Federal AE9, Winchester USA, M882) | $15–25 |
| Practice | Commercial 115-gr FMJ (Blazer Brass, S&B, Wolf steel-case) | $12–18 |
| Performance | Speer Gold Dot +P 124-gr, Federal 9BPLE +P+ 115-gr | $25–35 |
| Subsonic (suppressed Mk VI only) | 147-gr subsonic | Test thoroughly with the specific gun |
| Avoid | 9×18 Makarov, 9×17 Browning, 9 mm Largo | Wrong cartridges |
12.7 Vendor contacts
12.7.1 Parts kits
- Apex Gun Parts (Aurora, CO) — apexgunparts.com — canonical US STEN-kit vendor; 922(r) compliance docs included
- Sarco, Inc. (Stirling, NJ) — e-sarcoinc.com — alternate kits, sometimes higher-grade
- Indianapolis Ordnance — periodic STEN inventory; sometimes kit+receiver packages
- IO Inc. (Inter Ordnance) — io-inc.com — kits and US-made receivers as packages
- Numrich Gun Parts — gunpartscorp.com — individual replacement parts
12.7.2 US-made semi-auto receivers (Path B)
- Indianapolis Ordnance — pre-built closed-bolt receivers; $300–350
- IO Inc. — pre-built receivers; $250–300
- Wise Lite Arms — semi-auto STEN receiver shells; $280–320 (when available)
- 80% blanks — from various US suppliers; $100–180
12.7.3 NFA Class III dealers (Path A)
- InterArms — major Class III dealer with regular Sten inventory
- Bear Arms — bearcreekarsenal.com (also a manufacturer); Class III SOT dealer
- Subguns.com classifieds — community marketplace
- Sturmgewehr.com classifieds — community marketplace
- Rock Island Auction — NFA estate auctions; rockislandauction.com
- Morphy Auctions (formerly James D. Julia) — morphyauctions.com
- Amoskeag Auctions — amoskeagauction.com
12.7.4 Modern aftermarket parts (closed-bolt FCG, US-made replacements)
- Bear Arms — bear-arms.com — Sterling-pattern magazines, US-made stocks, closed-bolt FCG conversion kits, 922(r) compliance documentation
- ASP — Sterling-pattern magazines
- GunSpring — Sten/Sterling magazines with stronger springs
- Brownells — brownells.com — parkerizing supplies, chamber reamers, headspace gauges
- PTG (Pacific Tool & Gauge) — pacifictoolandgauge.com — 9×19 chamber reamers and gauges
- Manson Reamers — chamber reamers
12.7.5 Pre-rifled 9×19 barrel blanks
- E.R. Shaw — ershawbarrels.com — quality blanks; ~$80–120
- Green Mountain — gmriflebarrel.com — alternate vendor
- McGowen Precision Barrels — mcgowenbarrel.com
- McCory — alternate; sometimes less expensive
- Bear Creek Arsenal — bearcreekarsenal.com — budget-friendly
12.7.6 Finishing supplies
- Du-Lite Corporation — du-lite.com — manganese phosphate solutions
- Lauer Custom Weaponry — DuraBake parkerizing; gunsmith-market
- Brownells — bluing and parkerizing supplies
- NIC Industries — nicindustries.com — Cerakote (manufacturer)
- Birchwood Casey — birchwoodcasey.com — Tru-Oil, Sheath storage oil, Casey bluing
- Boyds Gunstocks — boydsgunstocks.com — Mk V wood furniture blanks
12.7.7 Attorneys (NFA practice)
- Prince Law Offices (PA) — princelaw.com
- Sean Brady (CA) — michellawyers.com
- Adam Kraut — [email protected]
- NFA Owners Association referrals — nfaoa.org
12.8 Bibliography
12.8.1 Engineering archive
- UK Ministry of Supply. SA-prefix drawings for Carbine, Machine, 9 mm STEN Mk II. National Archives Kew (WO 185, SUPP 5, AVIA 22 series); Royal Armouries Leeds; IWM Duxford. Crown Copyright under Open Government Licence v3.0.
- TM-E 9-1985-3. (US War Department, 1944.) Captured-arms catalog including Sten content. PD-USGov.
- FSTC 381-5012. Typical Foreign Unconventional Warfare Weapons (U). US Foreign Science and Technology Center. Wikimedia Commons PDF; declassified PD-USGov.
- Professor Parabellum. Practical Scrap Metal Small Arms, Volume III: The DIY STEN Gun. Wikimedia Commons CC BY 1.0 PDF. The canonical modern reverse-engineered drawing set.
- Bear Arms. STEN engineering drawings + 922(r) compliance sheet. Free download. The canonical US enthusiast 922(r) reference.
- Apex Gun Parts. Per-kit technical documentation. Mailed with each kit.
12.8.2 Collector reference literature
- Skennerton, Ian. The Sten Machine Carbine. The standard collector reference; per-Mk dimensioned summaries and factory variation.
- Iannamico, Frank. The STEN Submachine Gun. (Moose Lake Publishing, multiple editions.) Parallel-canon collector reference; deeper engineering detail than Skennerton on some Marks.
- Hogg, Ian V., and John Weeks. Military Small Arms of the 20th Century. General reference.
- Hogg, Ian V. Submachine Guns: An Illustrated History. Per-SMG-family treatment including STEN.
- Bishop, Chris. The Encyclopedia of Weapons of World War II. Production-volume facts.
- Smith, W.H.B., and Joseph E. Smith. Small Arms of the World. General-encyclopedic reference; cross-variant comparison.
12.8.3 Statutes and regulations
- 26 USC §§ 5801–5872 — National Firearms Act statutory framework.
- 18 USC § 921 — federal firearm definitions.
- 18 USC § 922(o) — FOPA-86 machine-gun manufacturing/transfer cutoff (May 19, 1986).
- 18 USC § 922(r) — non-importable-firearms parts-count rule.
- 27 CFR Part 478 — ATF regulations implementing the Gun Control Act.
- 27 CFR Part 479 — ATF regulations implementing the National Firearms Act.
- 27 CFR § 478.39 — the 20-parts list implementing 922(r).
- 27 CFR § 478.12 (2022) — definition of firearm including some 80% receivers (Vanderstok v. Garland pending).
- ATF Ruling 80-21 (1982) — closed-bolt-only rule for new semi-auto SMG designs.
- Rule 41F (2016) — fingerprints, photos, CLEO notification for NFA trust trustees.
12.8.4 ATF forms
Table 12 — 12.8.4 ATF forms
| Form | Purpose | Tax |
|---|---|---|
| Form 1 (5320.1) | Manufacture by individual (SBR, AOW, etc.) | $200 ($5 for AOW) |
| Form 4 (5320.4) | Tax-paid transfer of NFA item | $200 ($5 for AOW) |
| Form 5 (5320.5) | Tax-exempt transfer (estate) | $0 |
| Form 5320.20 | Interstate transport of NFA item | $0 |
| Form 5320.23 | Responsible Person Questionnaire (trustees) | $0 |
| Form 3310.11 | Lost/stolen firearm report | $0 |
12.8.5 Community archives
- Subguns.com — STEN forum and classifieds
- AR15.com STEN forum — community build threads
- Sturmgewehr.com STEN board — community archive
- NFA Owners Association (nfaoa.org) — owner-advocacy + legal resources
12.9 Recommended reading path for new builders
For a builder approaching the STEN deep dive for the first time, this order maximizes context-before-action:
- Vol 1 — Overview & Decision Tree. Decide which path.
- Vol 10 — Legal & Regulatory Posture. Confirm path is legal in the relevant jurisdiction.
- Vol 4 — Engineering & Reference Data. Understand the engineering.
- The path-specific volume (Vol 5 / 6 / 7) for the chosen build path.
- Vol 8 — Sub-Assemblies & Components. Deeper understanding of each part.
- Vol 9 — Materials & Finishing. Plan the finish before fabrication.
- Vol 11 — Live-Fire Operation & Use. Plan the break-in procedure.
- Vol 12 (this cheatsheet) — keep with the gun for ongoing reference.
Vols 2 (Manufacturing History) and 3 (Variant Catalog) are background reading; useful for context but not required before a build.
12.10 References (Vol 12)
This volume is a synthesis of Vols 1–11 of this series. All facts here are sourced from the originating volumes — see those volumes for the originating references. Specific cross-references this volume cites:
- Vol 1 — Overview & Decision Tree.
- Vol 2 — Manufacturing History.
- Vol 3 — Variant Catalog Mk I–VI.
- Vol 4 — Engineering & Reference Data (canonical dimensional source).
- Vol 5 — Build Path A (NFA Class III).
- Vol 6 — Build Path B (parts kit + US receiver + 922(r)).
- Vol 7 — Build Path C (from-scratch lab build).
- Vol 8 — Sub-Assemblies & Components.
- Vol 9 — Materials & Finishing.
- Vol 10 — Legal & Regulatory Posture.
- Vol 11 — Live-Fire Operation & Use.
../_shared/legal_ethics.md— hub-wide legal framework.../_shared/comparison.md— cross-build comparison matrix.../_shared/deep_dive_protocol.md— hub deep-dive workflow.
For a portable printable version of this cheatsheet, render the volume to PDF and laminate at 11×17″ or larger. Section headers are aligned for easy page-flip lookup.