British Sten MK3; new 9mm barrel w/BOTH trunnions
The Sten MK3 was the fastest and cheapest SMG Britain ever mass-produced. This kit comes with a new 9mm barrel and both trunnions. So it is one of the more build-ready Sten packages you will find at this price point.
What makes the British Sten MK3; new 9mm barrel w/BOTH trunnions different from the MK2?
The British Sten MK3; new 9mm barrel w/BOTH trunnions was built for pure wartime speed. First, the barrel is fixed — unlike the MK2 which had a removable barrel. Next, the receiver tube and barrel jacket were welded together as one piece. Also, the MK3 had no barrel nut or collar — fewer parts, faster production. Therefore, it was even simpler than the already simple MK2. However, that fixed barrel design means the new barrel in this kit is a significant component. Finally, over two million MK3s were made between 1941 and 1945.
What exactly is included and why do both trunnions matter?
This kit includes a new 9mm barrel plus both the front and rear trunnions. That combination matters. First, the trunnions are the structural anchor points of the Sten receiver — front and rear. Next, having both means you have the complete structural framework for a build. Also, a new barrel paired with serviceable trunnions gives you a solid foundation. However, many Sten kits come with worn or missing trunnions. So having both included here is a genuine advantage over typical surplus listings. Therefore, this is a more complete starting point.
What calibre is the British Sten MK3; new 9mm barrel w/BOTH trunnions and is ammo easy to find?
9mm Parabellum 9×19mm. The most common pistol calibre in the world. So yes, ammo is everywhere and inexpensive. Also, 9mm is used by NATO militaries, police forces, and civilian shooters globally. Therefore, running a British Sten MK3; new 9mm barrel w/BOTH trunnions based build is practical from an ammunition cost standpoint. But always verify headspace on any new barrel before live fire. Finally, confirm that the new barrel is dimensioned for standard 9mm Parabellum and not a less common variant.
| Product name | British Sten MK3 — new 9mm barrel, both trunnions |
| Caliber | 9mm Parabellum (9×19mm) |
| Era / origin | WWII — British military production |
| Barrel condition | New |
| Trunnions | Both front and rear included |
| Receiver included | No — required separately |
| Material | Steel stampings — wartime construction |
| Weight | |
| Best use | Semi-auto build, collector restoration, display |
| Price | £170 |
Is this kit better value than a standard Sten MK2 parts kit?
Different value, not better or worse. Here is the breakdown. First, the MK2 is more common and more recognised by collectors — higher name recognition. Next, the MK3 is rarer in complete kit form precisely because it was a disposable wartime design. Also, a new barrel included at £170 is strong value — a usable barrel alone is worth a significant portion of that. However, the MK3’s fixed barrel design makes it slightly simpler to work with than the MK2. Therefore, for a builder, the MK3 with new barrel and both trunnions at this price is excellent value. Finally, for a collector focused on MK3-specific variants, this kit is hard to beat.
What do I need beyond this kit to complete a build?
You need a legal registered receiver and a magazine at minimum. First, the receiver is the regulated firearm component — source it through a licensed dealer. Next, British Sten MK3; new 9mm barrel w/BOTH trunnions magazines are 32-round single-stack 9mm — original or reproduction options exist. Also, a bolt, recoil spring, and trigger group are required if not included. Therefore, treat this kit as the structural core — barrel and trunnions — of a larger build. But verify exactly which additional parts are and are not included in this specific listing. Finally, work with a qualified gunsmith for any functional build.
Frequently asked questions
What is the difference between the Sten MK2 and MK3?
What are trunnions on a Sten — and why do I need both?
Is the new barrel in this kit reproduction or original?
Can I legally build a Sten from a parts kit in the UK?
How many Sten MK3s were produced?
What magazines does the Sten MK3 use?
Is the Sten MK3 rarer than the MK2 in parts kit form?
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