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Pick parts. Check compatibility. Compare prices across retailers. Save and share your build.
Lower Receiver
Aero M4E1 Stripped Lower
Upper Receiver
Aero M4E1 Assembled Upper
Barrel
Ballistic Adv. 16" Hanson
BCG
Toolcraft Nitride BCG
Handguard
Midwest Industries 15"
Parts
Complete Rifles
Retailers
State Legal Guides
Compatibility Engine
Real-time validation catches incompatible parts before you buy. Platform, caliber, gas system, and barrel nut checks on every part.
Price Comparison
Same part, multiple retailers. Find the best deal without opening a dozen browser tabs.
Save & Share
Save your build with a shareable link. Get feedback from friends or the community before pulling the trigger.
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Compact 10.5" AR pistol build with a Faxon pencil barrel. Short, maneuverable, and easy to store. Uses a pistol-length gas system for reliable cycling. No stock configuration.
.300 Blackout Build
Short-barreled .300 Blackout build with a 7.5" Faxon Gunner barrel. Optimized for suppressed subsonic loads or supersonic punch in a compact package. Great for home defense or truck gun duty.
Budget Home Defense
A reliable, no-frills AR-15 for home defense on a budget. Proven brands, mil-spec components, and everything you need to get to the range without breaking the bank.
Shop Complete Rifles
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Great Lakes GL-15 223 Wylde/5.56, 7.5" Barrel, ORC Tungsten, Nitride, 30rd
via Impact Guns
Tippmann M4-22 LTE Accent 22 LR, 16" Threaded Barrel, Matte Black, Flat Dark Earth Accents, Flip Sights, M4 Stock
via Impact Guns
Freedom Ordnance FX9 9mm, 8" Barrel, Buffer Tube/No Brace, Uses ETS Glock Style Magazines, Include Bungee Sling, Black, 31rd
via Impact Guns
Smith & Wesson M&P FPC 5.7x28mm, 16.25" Threaded Barrel, Black, Flat Faced Trigger, 3x10rd Mags
via Impact Guns
Kel-Tec Sub2000 GEN3 9mm Luger 16.15in Black Semi Automatic Modern Sporting Rifle - 15+1 Rounds
SUB2K9GLKBLK
via Sportsman's Warehouse
Sierra 316l 5.56 Optic Ready Mlok (1x9)
ORFTML16-M2
via Brownells
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Shop
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Guides
Step-by-step build guides
Glossary
AR-15 terms explained
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50-state legal guide
Ballistics
Velocity, drop, energy tables
Specs
Mil-spec reference for every part
Gas System
Length, dwell, tuning calculator
Torque Specs
Every fastener, every value
Maintenance
Round count service schedule
Twist Calc
Optimal twist rate by bullet weight
Weight Calc
Estimate total rifle weight
Tools & Calculators
Plan, tune, and maintain your rifle with free interactive reference tools.
Gas System
Barrel length, dwell time, and buffer tuning
Weight Calculator
Target a build weight and find lighter parts
Maintenance Schedule
Round count based service checklist
Twist Rate Calculator
Find the right barrel twist for your bullet weight
Torque Reference
Every fastener torque spec and thread locker
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