What is a 5-Inch ARP Kit?

ARP here refers to a compact AR platform built around a 5" barrel. A typical 5" ARP kit includes nearly everything you need to finish a short-barreled AR pistol build except the stripped lower receiver (that serialized component must be purchased via an FFL). For official federal guidance on transfers and classifications, see the ATF resources.
External: ATF — Firearms Rules & Regulations

Common items found in 5" ARP kits:

• 5" Barrel — usually available in 5.56 NATO or .300 Blackout; check twist rate and finish on the product page.

• Durable Handguard — short, low-profile M-LOK or KeyMod handguards for accessory mounting.

• Lower Parts Kit (LPK) — triggers, selector, pins and springs for the lower.

• Optional BCG & Charging Handle — many kits include a BCG and charging handle; some let you add upgraded options.
  Shop BCGs → /ar-15/parts/bcg | Charging Handles → /ar-15/parts/charging-handles

Why Choose a 5-Inch ARP Kit?

• Compact Design: Short overall length for tight spaces (vehicle, home, or truck).

• Customizable: Swap optics, braces, muzzle devices, and accessories to tune the platform.

• Reliable Performance: Properly tuned micro gas systems and quality BCGs keep short-barrel builds running reliably.

• Cost Efficient: Buying a kit bundles compatible parts and typically saves money over buying components piecemeal.
  Shop accessories → /ar-15/accessories

Caliber Choices: 5.56 NATO vs .300 Blackout

• 5.56 NATO: Higher velocity and flatter trajectory — a good choice if you want more range and harder hits at distance.

• .300 Blackout: Optimized for short barrels and suppressed use — excellent subsonic and short-barrel performance.

If you’re unsure which fits your goals, read our Barrel Length & Gas System Guide → /guides/barrel-lengths.

Build Tips & What to Inspect

Before you start building, verify the kit’s specs and plan your tools:

• Confirm whether the kit includes a BCG and charging handle or if those are optional upgrades.

• Check barrel finish, twist rate, and gas system length (pistol vs carbine/mid).

• Use proper armorer tools and follow a clean workspace routine. If you prefer, have a qualified gunsmith verify headspace and final function.

Legal & Compliance — Know the Rules

Laws vary by state and change over time. Before purchasing or finishing your build:

• Review federal guidance: ATF — Firearms Rules & Regulations

• Check state and local ordinances: ATF — State Laws & Published Ordinances.

• Be mindful of pistol braces vs. stocks, vertical foregrip rules, and NFA items (suppressors, SBRs). If you intend to SBR or suppress, follow NFA procedures and consult official guidance.

Shop ARP Kits & Uppers

Ready to build? Start with the component that matters most — the upper — or grab a complete kit:

• Shop 5" AR Pistol Kits → /ar-15/pistol-kits/5-inch

• Shop 5" Uppers → /ar-15/uppers/5-inch

• Browse All AR Kits → /ar-15/pistol-kits
  Don’t forget mags, braces, and optics: Accessories → /ar-15/accessories

Final Thoughts

The 5" ARP kit is a smart choice for shooters who want a compact, capable AR pistol without sacrificing performance. With the right barrel, a tuned gas system, and a quality BCG, you’ll have a dependable short-barrel platform that’s easy to carry, customize, and enjoy at the range.

Questions or want product recommendations? Check our product pages above or contact customer support — and always verify legal compliance before completing your build.