Senex Arms MBLR-15 Prototype: The Bullpup Built for the Average Joe (SHOT Show 2022 Look Back)

Squat Squad, this one is a look back to SHOT Show 2022 (video published December 9, 2022), and it’s where the whole Senex Arms story started for this channel. Over the last few years everybody got the Tavor itch. Bullpups grew into a real product class, and in a small booth on the show floor I found one of the products that really caught my attention: the Senex Arms Modular Bullpup Light Rifle 15, or MBLR-15.

Brandon, the owner of Senex Arms and the guy who invented the rifle, walked me through it. The pitch is simple: a bullpup that runs common AR-15 components, so you’re not stuck in one caliber the way you are with most bullpups.

Quick note: this was a SHOT Show 2022 booth first look at an early prototype, not a SlavGuns range test and evaluation. Nothing was fired on camera, and Brandon was clear that the design was still in development. If you want to see where the rifle went a year later, check out our People’s Bullpup SHOT Show 2023 update.

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The origin story: a Tavor, a gun store and a stubborn Marine

The 2023 article covers the upgrades. This video is the first conversation, and the part I liked most is why the rifle exists. Brandon studied engineering, then joined the Marine Corps and became a reconnaissance Marine. An injury forced him out, so he opened a gun store to learn more about firearms. When the Tavor X95 came out he bought one and loved it, but it came in one caliber. 5.56 is great, but sometimes you want to be a little adventurous.

That’s where the idea came from, back in 2015: a bullpup that uses the AR-15 parts people already own and already know. When I asked him to confirm that barrel, trigger group and pistol grip were all AR parts, his answer was yes, plus the gas system.

The barrel swap, as demoed

Brandon pulled the barrel on camera (and warned me it wouldn’t go back together well because we were filming):

1. Drop the magazine. There are three mag release points, so if one linkage ever fails you still have two more.
2. Pull the bolt to the rear and lock it up, kind of like an MP5. Yes, I asked if we could HK slap it. Yes, we did.
3. Pull the small lever back, rotate it 180 degrees up and forward, and the barrel slides out. It’s a cam lock setup.
4. Reverse it to install, put the magazine in, and you’re good to go.

Brandon’s point was that this type of system isn’t exotic. He compared it to the MDR and the Tavor. His philosophy: there’s no single feature on this rifle you haven’t seen somewhere else, but nobody had put them all together in one comfortable, ergonomic package.

Return to zero? He didn’t oversell it

My question with any quick-change barrel is repeatability. Brandon explained that a slightly larger diameter section seats and locks the barrel in when it rotates in, to the point you have to fight it a bit. But he was honest: at that point he hadn’t done any testing to confirm return to zero and didn’t want to claim anything that might not be accurate. I respect that a lot more than a booth guy promising sub-MOA forever.

Built for the average Joe

This is where the video title comes from. Brandon described himself as a one-man show and a single dad, and said he wasn’t going to build something he couldn’t afford himself. He felt a lot of the great brands at the show were out of reach for the average gun owner, and he wanted the MBLR-15 to be accessible. No target price was given, and Senex hasn’t announced one, so I’m not going to guess.

How Brandon planned to sell it (in 2022)

• Calibers: probably 5.56 and 300 Blackout, possibly in a couple of barrel lengths.
• Barrel length and OAL: the show rifle had an 18-inch barrel at about 27.4 inches overall, just over the minimum overall length. Canadians had been asking for a 20-inch barrel.
• 16-inch option: an extended butt pad to keep a 16-inch barrel at a legal overall length.
• Builder’s kit: a version without some components like barrel, pistol grip or bolt, so you can use parts you like.
• Two barrel nuts with every gun: the two-piece barrel nut is what interfaces with the rifle, so your first caliber change doesn’t require going back to Senex.
• Aftermarket: since the trigger is an AR-15 design with only the trigger itself modified, existing aftermarket parts should mostly carry over.
• Pre-orders: possibly tiered pre-sales with different numbers of barrel nuts. Nothing was final.

Where it is now

Brandon hoped to have it out before the next year and immediately told me not to hold him to that. Good call. A year later at SHOT Show 2023 the rifle had moved from mostly 3D printed parts toward metal operating parts (that’s the People’s Bullpup article). As of this writing, the Senex Arms product page still lists the MBLR-15 as in R&D and not yet available for purchase or pre-order. Check senexarms.com for the latest.

Our take

I like this concept for the same reason I liked it in 2022. AR-15 parts are everywhere, so a bullpup that lets you swap barrels and calibers with parts you can actually find is a smart idea. The quick-change barrel was simple, the three mag releases are a nice touch, and Brandon was refreshingly honest about what he hadn’t tested yet. The flip side is just as honest: this was a prototype at a booth, and years later it still isn’t something you can order. Senex isn’t the only one chasing the AR-parts bullpup idea, either. PSA showed its Jackal Odin bullpup concept at SHOT Show 2024. If you like modular rifles, the MBLR-15 is one to keep an eye on.

Links

• MBLR-15 status and updates: Senex Arms
• Precision rifle upgrades: Anarchy Outdoors
• Everything else I run: SlavGuns Amazon storefront
• Support the channel: join the Squat Squad on YouTube

Would you run an AR-parts bullpup in 300 Blackout, or does a bullpup need to be 5.56 to make sense? Let me know in the comments. Thanks for reading, and keep on squatting!

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