Adjustable Binary Spring Kit
Video review
Expert review
About this product
What is the Binary Logic Arms Adjustable Binary Spring Kit? This three-spring set provides precise, mechanical tuning of binary trigger function across different ammunition and buffer systems. It's the primary tool for enthusiasts who demand reliability beyond factory specifications, allowing you to dial in ignition force and reset timing to match your specific setup. While many shooters accept factory spring rates as final, our kit recognizes that consistent binary function requires adjustment for variables like primer hardness, carrier mass, and lubrication state.
What is the Adjustable Binary Spring Kit used for?
The Adjustable Binary Spring Kit allows you to systematically tune the mechanical behavior of your binary trigger system. You use it to correct failures like light primer strikes or hammer follow by adjusting spring force and timing. The included shims enable preload adjustment of the disconnector spring, affecting its release timing by ±5 milliseconds, which is critical when pairing with heavier buffer systems or when using ammunition with varying primer sensitivity. This mechanical tuning is essential for achieving reliable binary function beyond the narrow parameters covered by standard springs.
How does the Adjustable Binary Spring Kit compare to McMaster-Carr springs?
The Binary Logic Arms kit is specifically engineered for binary trigger geometry, while McMaster-Carr springs are general-purpose industrial components. Our hammer spring provides 10% more force than a standard AR-15 hammer spring with 22 coils, achieved through 24 coils of chrome silicon wire. More importantly, our springs maintain dimensional consistency and modulus across the -40°F to 250°F temperature range, whereas McMaster-Carr springs typically have wider tolerances (±15%) that can cause inconsistent sear engagement. For binary triggers where geometry is critical, our kit is superior for reliability.
What does it weigh and what are the dimensions?
The complete kit weighs 1.4 ounces, packaged in a rigid polymer case measuring 3.25 inches by 1.75 inches by 0.625 inches. Each individual spring is dimensionally optimized for AR-15 fire control groups; the trigger spring uses 0.021-inch wire diameter with progressive winding that increases resistance linearly through the pull. The hammer spring measures 0.312 inches in diameter with a free length of 1.125 inches. The small size and weight mean it integrates into any range bag or toolkit without adding bulk.
Who is this NOT for?
This kit is not for casual shooters who don't experience binary reliability issues or who aren't prepared to diagnose trigger function failures. If you run only high-quality, consistent ammunition through a standard carbine setup and your FRT-15 Drop-In Trigger Module works perfectly, this level of tuning provides minimal benefit. Additionally, if you're unwilling to disassemble your lower receiver or lack basic spring installation tools, this product creates more frustration than solutions. Read our technical guide on hammer follow prevention to understand the problems this kit solves before purchasing.
What's in the box?
The box contains three precision-ground springs and a set of tuning shims. Specifically, you receive one hammer spring (24 coils), one progressively wound trigger spring (0.021-inch wire), and one disconnector spring with a rate of 1.8 lb/in. The kit includes five stainless steel preload shims in thicknesses of 0.005, 0.010, and 0.020 inches for modifying disconnector spring timing. All components come in a numbered, compartmentalized case with installation guidance referencing our technical framework for mil-spec lowers.
Is the Adjustable Binary Spring Kit worth it at $29.99?
At $29.99, the kit delivers exceptional value if you've experienced binary reliability failures. Spending three hours troubleshooting light primer strikes or hammer follow at the range costs more in ammunition and frustration than this mechanical solution. Compared to shipping a trigger back to the manufacturer for adjustment (typically $25-40 plus shipping time), this kit puts permanent tuning capability in your hands. For competitive shooters running FRT-compatible Bolt Carriers with varying reciprocating mass, these springs are essential equipment for maintaining split times under 80 milliseconds.
Specs at a glance
Pros & cons
What works
- Chrome silicon material maintains modulus across -40°F to 250°F temperature range — zero performance drift
- Hammer spring provides 10% more force with 24 coils versus standard 22 coils — ensures positive ignition with hard primers
- Preload shims adjust disconnector release timing by ±5 milliseconds — critical for buffer system synchronization
- Trigger spring uses 0.021-inch progressive winding — creates linear resistance increase through pull
Trade-offs
- No installation tool included — requires your own spring installation tool or improvised method
- Requires complete lower disassembly for installation — adds 20-30 minutes versus drop-in components
- Limited color coding — all springs are silver finish, requiring careful identification during installation
Key attributes
| Material | Chrome silicon wire |
| Temperature Range | -40°F to 250°F |
| Hammer Spring Coils | 24 |
| Trigger Spring Wire Diameter | 0.021 inches |
| Disconnector Spring Rate | 1.8 lb/in |
| Preload Adjustment | ±0.020 inches |
| Compatibility | Mil-spec AR-15 trigger groups |
| Contents | 3 springs, 5 preload shims |
Specifications
| Hammer spring coils | 24 |
| Trigger spring wire diameter | 0.021 inches |
| Material | Chrome silicon |
| Temperature range | -40°F to 250°F |
| Preload adjustment | ±0.020 inches |
| Disconnector spring rate | 1.8 lb/in |
Best for
- Tuning binary triggers for reliable function with steel-case ammunition
- Adjusting release timing to match specific buffer and bolt carrier weights
- Restoring crisp break to worn binary systems without replacing entire components
Materials
- Chrome silicon wire
- Stainless steel shims
What's in the box
- Hammer spring
- Trigger spring
- Disconnector spring
- Shim set (5)
Care
Frequently asked questions
- Is it compatible with Franklin Armory BFS-III triggers?
- Yes, this kit is fully compatible with the Franklin Armory BFS-III series. The hammer spring directly replaces the stock component, though we recommend starting with the lightest preload shim when tuning the disconnector spring, as the BFS-III has different geometry than our own Binary Logic BFS-III Trigger Group. Expect installation to require approximately 15 minutes with proper tools.
- Does it fit Anderson Manufacturing lowers?
- It fits all mil-spec AR-15 lowers, including Anderson Manufacturing models, provided your trigger pocket dimensions are within standard specifications. We've tested across 47 different lower receivers from 12 manufacturers and encountered no compatibility issues. The springs require standard fire control group pin diameters of 0.154 inches, which Anderson Manufacturing consistently maintains.
- How long does shipping take?
- Standard shipping typically delivers within 3-5 business days for continental US orders placed before 2 PM Eastern. We ship via USPS Priority Mail from our Mesa, Arizona facility, which provides tracking within 4 hours of label creation. Expedited 2-day service is available at checkout for an additional $12.
- Can I return it if it doesn't solve my reliability issues?
- Returns are accepted within 30 days if the product is unused and in original packaging. However, we strongly recommend consulting our technical guides first—most binary reliability issues stem from improper installation or other component compatibility, not the springs themselves. If you've installed the springs and still experience problems, our support team will diagnose your specific setup before processing any return authorization.
- Does this work with enhanced nickel boron bolt carriers?
- It works with all bolt carriers, including enhanced nickel boron models. However, the increased carrier mass and reduced friction of nickel boron coatings can affect lock timing, requiring adjustment of the disconnector spring preload. Start with the 0.010-inch shim and test for hammer follow over 50 rounds, adjusting as needed. The chrome silicon material maintains consistent performance regardless of lubrication state.