Methodology

Parts Data Sources

Our parts catalog is built from product feeds provided by affiliate networks (CJ and Impact.com) through AvantLink. We ingest data from multiple authorized retailers including Brownells, Sportsman's Warehouse, and Sportsman's Guide.

Each product feed provides: part name, brand, SKU, description, pricing, product images, and affiliate tracking URLs. We normalize this data across retailers to create a unified parts database organized by category (lower receiver, upper receiver, barrel, BCG, handguard, and 10 additional categories).

Part Classification

Not everything in a retailer feed is a buildable part. A "BCG" category might include gas key screws, cleaning brushes, and extractor springs alongside actual bolt carrier groups. We use a three-layer classification system to separate primary parts from accessories:

• Price floors: each category has a minimum price threshold (e.g., a BCG under $50 is likely an accessory)
• Keyword filtering:terms like "screw," "spring," "detent," and "cleaning kit" indicate accessories
• Name pattern matching:parts must match category-specific patterns (e.g., "bolt carrier group") and not match exclusion patterns (e.g., "extractor")

Only parts classified as "primary" appear in the builder. Accessories are excluded to keep the configurator focused on buildable components.

Compatibility Engine

The compatibility checker uses a data-driven rules engine. Rules are stored in a database table, not hardcoded, which allows us to add and update rules without code changes. Each rule specifies:

• A source category and spec key (e.g., barrel caliber)
• A target category and spec key (e.g., BCG caliber)
• An operator and expected relationship (e.g., must match)
• Severity level: error (will not work), warning (may cause issues), or info

Rules are evaluated client-side in real time as you add parts to your build. The engine checks platform compatibility (AR-15 vs AR-10), caliber matching, gas system length, barrel nut compatibility, and buffer tube type among other factors.

Pricing Aggregation

Each part may be listed at multiple retailers. We display the lowest available price by default and allow you to compare prices across all retailers that carry a given part.

Prices are synced nightly via an automated cron job that re-fetches current pricing from retailer feeds. Price history is tracked over time, enabling the sparkline price charts visible on each part card.

All prices shown are the retailer's listed price at the time of our last sync. Actual prices at checkout may differ due to sales, coupons, shipping costs, or timing differences.

NFA Classification Checker

The builder includes an NFA (National Firearms Act) status indicator that evaluates your build configuration against federal regulatory thresholds. This checks factors such as:

• Barrel length (under 16" may indicate a short-barreled rifle)
• Overall length (under 26" may trigger additional classification)
• Stock type vs. brace (affects pistol vs. rifle classification)

NFA rules are stored in the same data-driven format as compatibility rules and are evaluated in real time. This feature is informational only and does not constitute legal advice. Federal, state, and local laws vary. Always consult a licensed attorney before building.

Data Freshness

• Pricing: synced nightly via automated job. Prices may be up to 24 hours old.
• Parts catalog: new products are added as retailer feeds update. Discontinued products are retained with historical pricing.
• Compatibility rules: updated manually as we identify new compatibility requirements or receive community feedback.
• State legal data:reviewed periodically. Each state page shows a "last verified" date.

Limitations and Disclaimers

The AR15 Outfitters builder is a reference tool, not a guarantee of compatibility. While we work to keep data accurate, there are inherent limitations:

• Manufacturer specs change without notice. A part that was compatible last month may have been revised.
• Our classification system may occasionally miscategorize a part as primary or accessory.
• Stock availability is not tracked in real time. All listings default to "in stock." Actual availability is the retailer's responsibility.
• Not all compatibility factors can be captured in a rules engine. Some fitment issues (e.g., handguard inner diameter tolerances) require hands-on verification.
• NFA and state legal information is educational only. Laws change frequently and vary by jurisdiction.

For critical compatibility questions, consult the manufacturer or a qualified gunsmith. For legal questions, consult a licensed attorney. Found an issue with our data? Please report it on our contact page.