MX556 Gen 2 AR15 Rifle – 5.56 NATO, 4150 CMV Nitride Barrel, Mid-Length Gas, RG2 Wedge Lock Rail, Microbest Chrome BCG, Elftmann Trigger
MX556 Gen 2 Rifle – 5.56 NATO | Mid-Length Gas | Precision-Built Performance
The MX556 Gen 2 Rifle represents the next level of AR15 performance—engineered with elite-grade components, tuned for reliability, and precision assembled by experienced builders.
Founded by engineers and building rifles since 2014, Mid State Firearms approaches every platform with a focus on mechanical efficiency, proper tolerances, and real-world performance—not just parts selection.
This is a fully realized system, built to run under pressure and perform without compromise.
Purpose-Built Performance – Component by Component
4150 CMV Nitride Barrel – 1/7 Twist | Mid-Length Gas System
- 4150 Chrome Moly Vanadium steel for superior strength and heat resistance
- Black nitride finish for increased wear life and corrosion resistance
- Mid-length gas system for smoother recoil and reduced component wear
- M4 feed ramps for reliable feeding under all conditions
- 1/7 twist stabilizes a wide range of modern bullet weights
RG2 Rugged Rail – Wedge Lock System
- True free-float M-LOK rail for enhanced accuracy
- Wedge lock system provides exceptional rigidity and zero shift
- Built for hard-use applications and accessory mounting without compromise
Microbest Chrome BCG – Fully Upgraded & Duty-Ready
- C158 Carpenter steel bolt (true mil-spec material)
- Individually HPT/MPI tested (not batch tested)
- Hard chrome carrier for reduced friction and easier cleaning
- Sprinco extractor and ejector springs for improved reliability
- Permatex-sealed gas key (mil-spec sealing method)
- OCKS gas key screws for superior long-term retention
This is a serious-use BCG, designed to outperform standard mil-spec options in both durability and consistency.
Elftmann Competition Adjustable Trigger
- Crisp, clean break with minimal creep
- Adjustable pull weight
- Fast reset for precision and speed
Gas System & Reliability Enhancements
- .750 steel low-profile gas block for durability and consistent gas delivery
- Stainless steel gas tube for corrosion resistance and long service life
Upper Receiver – True Mil-Spec Foundation
- 7075-T6 aluminum construction
- Type III hardcoat anodized finish
- M4 feed ramps
- Forward assist and dust cover installed
Furniture & Ergonomics
- Rogers Super Stock – lightweight, stable, and secure lockup
- Magpul K2+ Grip – improved angle and enhanced control with rubber overmold
3-Prong Closed Tine Flash Hider
- Reduces flash signature in low-light conditions
- Closed tine design minimizes snagging
- Durable and suppressor-conscious configuration
Why Choose the MX556 Gen 2 Over Competitors?
In a market filled with well-known names, the MX556 Gen 2 is built for those who look beyond branding and focus on what actually matters inside the rifle.
Built by Engineers – Not Just Assembled on a Line
Large manufacturers prioritize volume. We prioritize precision, fitment, and function. Every rifle is assembled with attention to gas system balance, torque specs, and component interaction.
Higher-End Components Where It Counts
Many rifles in this price range still use:
- Batch-tested bolts
- Standard extractor springs
- Basic gas key hardware
The MX556 Gen 2 upgrades critical failure points with:
- Individually tested C158 bolts
- Sprinco spring upgrades
- OCKS fasteners and sealed gas key
These are the details that impact long-term reliability—not just spec sheets.
Better Shooting Characteristics Out of the Box
The mid-length gas system, properly tuned assembly, and premium trigger combine to deliver:
- Smoother recoil impulse
- Faster follow-up shots
- Improved consistency
No need to “fix” the rifle after purchase.
True Value
Instead of paying for brand name alone, you’re getting:
- Premium internal components
- Enhanced durability upgrades
- Careful, experienced assembly
All in a rifle designed to run hard and last.
Proven Experience Since 2014
Mid State Firearms has been building AR platforms for over a decade, with a foundation rooted in engineering principles and real-world use—not trends or shortcuts.
Built by Professionals – Ready for Anything
Every MX556 Gen 2 rifle is:
- Properly torqued and assembled
- Gas system aligned and verified
- Function tested and inspected
The result is a rifle that delivers confidence from the first round to the last.
Key Specifications
- Caliber: 5.56 NATO
- Barrel: 4150 CMV, Black Nitride, 1/7 Twist
- Gas System: Mid-Length
- Gas Block: .750 Steel Low Profile
- Gas Tube: Stainless Steel
- Handguard: RG2 Rugged Rail with Wedge Lock
- Upper Receiver: 7075-T6, Type III Anodized
- Bolt Carrier Group: Microbest Chrome (C158, HPT/MPI, Sprinco, OCKS, Permatex Seal)
- Trigger: Elftmann Adjustable Competition Trigger
- Stock: Rogers Super Stock
- Grip: Magpul K2+
- Muzzle Device: 3-Prong Closed Tine Flash Hider
The Bottom Line
The MX556 Gen 2 is built for shooters who understand that performance is earned through component quality, engineering, and proper assembly—not shortcuts.
If you’re investing in a rifle to last, this is the platform that delivers where it actually counts.

sound of freedom – This was a great set up. I loved being able to customize the set up. Only issue I had was my own fault as a newb to building these. I used a heavy barrel in a slim hand guard. It makes adding attachments tough with clearances. Hoping someday to also get an AR10 from here.