Product Description
2022 Update: For 2022 we are introducing the new Internally Threaded Pattern (ITP) assemblies of the Stemple 76/45 receivers to offer a more streamlined and versatile system with enhanced compatibility among setups. Per this previously approved method of attaching the trunion, separate trunions and bolt guides are no longer necessary for converting between the standard and heavy bolt systems. While these can still be used on the receiver, one trunion now does it all. For example, the previous U9 conversion to the U9 slow fire setup required separate trunions/bolt guides, bolts, stocks, and buffers. In the ITP setup only the stock and buffer assemblies are switched to add mass to the moving parts for lower cycle rates. The bolt and trunion are unchanged. The fire controls, stocks, and mag housings are also unchanged.
The STG1928 parts are also fully compatible with this setup.
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Transferable
In 2003, the original inventor, John Stemple collaborated with BRP Corp to make new and replacement parts for the Stemple 76/45 receivers he manufactured prior to the 1986 cutoff. From this came a series of compatible drop-on parts for the unmodified/transferable Stemple 76/45 receivers known as Stemple Takedown Gun (STG) setups. Since nothing is welded or hand fitted to these receivers, changing setups and replacing parts is fast and easy. These are the most finely built and smooth running sub-machine guns on the transferable market. We build them for performance and durability, stock plenty of high-quality spare parts, and provide excellent service.
Caliber: 9mm
Capacity: Suomi 70-rd & 36-rd mags; Swedish M37/M45 25-rd and 50-rd “coffin” mags
Sights: Finnish KP31 & Picatinny compatible
Cycle Rate: 750-950 (full-auto-only)
Barrel Length: 12.75” with KP31 shroud or Short Steel Shroud with 8.6" barrel (threaded and 3-lug barrel setups also available)
Parts and Accessories Included With Each Gun: 1 x 36rd magazine, 1 x 70rd drum, multi-tool, spare buffer, and 2 spare picatinny accessory rails for the shroud mount bipod and top optic mount.
3 Patterns Available:
1) Finnish Standard M31 Slant-Cut Shroud with removable bipod rail (12.75 in. barrel)
2) Finnish Compensated M31 Shroud with removable bipod rail (12.75 in. barrel)
3) Short Steel Shroud compatible with Atlas BT-15 rail mounts and used with 8.6" threaded or unthreaded barrels
Simple / Durable Design:
Our guns are very difficult to break and very easy to fix. They are simple blow-back guns and very smooth-running in long full-auto bursts. Some of our customers who own the 9mm guns liken the full-auto performance to a laser beam.
Easy-to-Replace Parts:
There's nothing on these guns that cant be easily replaced. We designed this system to protect the registered receiver from any wear during use. The only parts that can wear can be easily replaced without the need to ship the gun back-and-forth.
Available Service:
If you need service, we are here to support our products.
Shoot Cheap Ammo:
We typically just shoot steel-cased ammo. Our milled steel trunions easily deal with potential wear issues from any type of ammo.
Capacity and Control: These guns use 70 round drums and are smooth cycling, heavy, accurate, and comfortable to hold. It's basically an assault rifle with a sub-caliber setup... a very controllable and accurate gun in full auto. It's so smooth due to the weight, layout, and action; you can actually watch your target being hit through a 4x scope while shooting long bursts. The 'laser beam' performance of this gun makes it one of the most enjoyable full auto guns you'll ever shoot.
Can't Get Too Hot: These are ideal for machine-gun shoots. The low-pressure 9mm round cannot create enough heat in the barrel to cause a malfunction or damage the gun. There's no gas system to clog, and the open-bolt system negates any cook-off risk.
Product Videos
Videos Hide Videos Show Videos
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Submachine Gun - Suomi 31 - Nick
Nick shooting Suomi 31 at Knob Creek gunrange, Kentucky 1209
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Submachine gun - Suomi 31 - Keith
Keith shooting Suomi 31 at Knob Creek gunrange, Kentucky 12-09
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Stemple Suomi
Finnish KP31-Based Setups Just about all of the parts we make...
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Ian Takes the Pepsi Haaste: Suomi vs Stemple-Suomi
http://www.patreon.com/ForgottenWeapons https://www.floatplan...
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BRP Recreates a Classic: the Stemple-Suomi
http://www.patreon.com/ForgottenWeapons https://www.floatplan...
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Full Auto Suomi in the 2021 AZ PCC Championship
http://www.patreon.com/ForgottenWeapons https://www.floatplan...
Custom Field
Product Reviews
6 Reviews Hide Reviews Show Reviews
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At the MG Shoot....
A few of my neighbors and I went out to the Big Sandy Machine Gun Shoot. We took one of your Suomi guns and a STG 1928. They ran like well oiled machines. Thank you for making such a great product!
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Fantastic smg, runs great. Well made and fun to shoot!
Great gun.
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M31 Suomi
The m31 Suomi is my favorite subgun and this version from Brian and BRP is very close. The differences in design are very well covered by Ian from the Forgotten Weapons YouTube channel. Minus the design differences they handle and fire identically. If I was blindfolded I’m not sure if I’d be able to tell the original apart from the BRP version. I’m also a fan of the side charging handle instead of it being on the rear of the receiver. Brian and the BRP company are always a pleasure to deal with and I’d definitely recommend this subgun to anyone who is a fan of the Suomi style of machine guns.
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Absolutely Fantastic
Brian, Finally out of jail and in hand. This thing is a hoot to shoot. Runs great, zero issues, absolutely fantastic. Thanks so much for a sweet build. Can’t wait to let Dad do some mag dumps for Father’s Day next month! Hope y’all are doing well. Looking forward to visiting GA sometime. Take care! Sincerely, Don in VA
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Great
Had tons of fun with your guns.
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Subgun At Its Best
I purchased this full auto Stemple Suomi 9mm based on the Finnish KP31. Upon receipt I observed that it was extremely well packaged and in perfect condition. After reading the very informative and easy to follow manual, it took only minutes to install the barrel and shroud. On the range for the first time (and every time since) I loaded the 70 round drum with inexpensive ammo and was thoroughly pleased how smoothly and cool it fired. Recoil was enjoyably light, too. And, there haven’t been any malfunctions at all. In addition, if there is such a thing as a tack driver in a subgun, this is it. I highly recommend BRP for their outstanding products, knowledge and dedicated support. Thank you Brian, for everything!
