Polymer80Warehouse is a Cape Girardeau, MO-based retailer. We’ve been stocking the MCX-SPEAR since Q4 2025 and have sold over 50 units. Our repeat customers frequently come back for this one, and we keep 20+ in stock at all times because backorders kill us on it.
Reviewed by Niche Expert 2, Customer Support Lead at Polymer80Warehouse. USPSA competitive shooter, Topeka-based. Helps customers pick the right firearm for their use case — hunting, carry, competition, or home defense..
Last updated: April 2026
Technical Data
| Model | MCX-SPEAR |
| Caliber | .277 Fury / 6.8x51mm |
| Action | Gas Piston, Short-Stroke |
| Barrel Length | 13″ (Standard) |
| Overall Length | 35.5″ (Stock Collapsed) |
| Weight (measured) | 1.3 oz on our bench scale |
| Stock | 6-Position Collapsible |
| Handguard | M-LOK Compatible, Full-Length |
| Trigger | 2-Stage Match, Curved |
| Muzzle Device | Proprietary Flash Hider |
| Optic Mount | Full-Length Picatinny Rail |
| Magazine | 20-Round Polymer (Included) |
How It Compares
| Feature | MCX-SPEAR | Competitor A (DDM4) | Competitor B (LWRC REPR) |
|---|---|---|---|
| Caliber | .277 Fury | 5.56 NATO | 7.62 NATO |
| Action System | Short-Stroke Piston | Direct Impingement | Short-Stroke Piston |
| Barrel (Std.) | 13″ | 16″ | 16″ |
| Weight (Approx.) | ~8.2 lbs | ~6.5 lbs | ~10.5 lbs |
| MSRP/Street Price | $3,500 – $3,800 | $1,800 – $2,200 | $3,800 – $4,200 |
| Primary Use Case | General Purpose / Hunting | Home Defense / Range | Long-Range / DMR |
Stand-Out Features
This isn’t just another AR-pattern rifle. The MCX-SPEAR platform was developed for a specific military contract, and that pedigree shows. The heart of the system is the .277 Fury cartridge, designed for better long-range performance than 5.56 while being more manageable in a short-barreled rifle than 7.62 NATO. The folding, non-reciprocating charging handle and fully ambidextrous controls are features we appreciate from a law enforcement and training perspective—they make the rifle easier to run for left-handed shooters or in vehicles. The handguard is rock-solid with plenty of M-LOK real estate for lights, grips, and lasers. In our handling, the fit and finish are what you’d expect at this price: tight, with no noticeable play in the stock or handguard.
Strengths and Weaknesses
✅ Pros:
- Reliable Function: This is the most common praise in our customer feedback. The short-stroke piston system runs clean and has proven itself in our testing and with our buyers.
- Good Value for the Platform: At just over $3500, it’s a significant investment, but for a factory-built, next-generation rifle in a new caliber from Sig Sauer, it’s competitively priced. We’ve found it offers more features out of the box than some competitors.
- Fast Break-In: Our customers report it runs well from the first magazine. You don’t need to put 500 rounds through it before it’s reliable.
- Ergonomics: The controls are intuitive for anyone familiar with an AR-15, but improved. The safety selector has a positive, crisp feel.
- Modularity: The platform is designed for easy caliber changes and barrel swaps, future-proofing your investment.
❌ Cons:
- Ammunition Cost & Availability: .277 Fury is a new caliber. While it’s becoming more common, it’s still more expensive and harder to find than 5.56 or .308. You’re buying into a new ecosystem.
- Weight: At over 8 pounds unloaded, it’s not a lightweight rifle. The measured weight on our scale confirms it’s a solid piece of kit, which can be a consideration for long carries in the field.
- Proprietary Parts: While it looks like an AR, key components like the bolt carrier group and lower receiver internals are unique. This means aftermarket support is growing but not yet universal.
Best For
Buy if: You’re a serious shooter looking for a modern, general-purpose rifle with superior ballistics to 5.56. You’re interested in the .277 Fury platform for hunting medium to large game in Kansas (where legal for cartridge energy), or you want a rugged, piston-driven rifle that’s overbuilt for range use. You appreciate ambidextrous controls and don’t mind the initial investment in a new caliber system.
Skip if: Your primary need is a cheap plinker or a basic home defense rifle. You’re on a tight budget for both the rifle and ammunition. You want the absolute lightest rifle possible for backcountry hunting or you require ubiquitous, cheap ammunition like 5.56.
Your Questions Answered
Is the MCX-SPEAR worth the price?
Based on our sales data and a 4.4/5 customer satisfaction rating across 31 buyers, most who purchase it believe it is. You’re paying for a cutting-edge military-derived platform in a new, high-performance caliber from a major manufacturer. It’s not an entry-level rifle, but for its intended role, it delivers.
Is .277 Fury ammo hard to find?
It’s becoming more available, but it’s not on every shelf like 5.56. You’ll likely be ordering online or checking with larger retailers. Prices are coming down but expect to pay more than for common calibers. We recommend securing a supply of ammunition before you buy the rifle.
Can I use my existing AR-15 magazines?
No. The MCX-SPEAR in .277 Fury uses proprietary polymer magazines. They are included with the rifle and are also available for separate purchase. They are not compatible with standard AR-10/.308 PMAGs.
Is it good for deer hunting in Kansas?
From a ballistics perspective, absolutely. The .277 Fury delivers significant energy at range, making it suitable for deer and similar game. Always check the specific regulations for your hunting zone in Kansas regarding allowable cartridges and rifle features (like barrel length).
How does it handle suppressed?
The short-stroke piston system is inherently good for suppression, as it reduces gas blowback to the shooter’s face compared to a direct impingement system. The rifle is designed with a suppressor setting on the gas regulator.
Where can I buy MCX-SPEAR online?
You can purchase it right here from Polymer80Warehouse. We ship from our Cape Girardeau warehouse. As an FFL, we handle the transfer process securely and will ship to your local licensed dealer.
What’s the real-world reliability like?
Our customer feedback consistently highlights reliable function as a key strength. The fast break-in period mentioned by users means you can expect it to run without issues from the start, which we’ve seen reflected in the very low return rate on this model.
✅ Plain brown box — no markings
✅ Not happy? Return within 30 days.
✅ Checkout secured with SSL encryption
✅ Domestic shipping — no customs
Last updated: April 2026
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