Lower Parts
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Lower parts guide for AR-15 builders
Buffer and buffer tube selection: A standard carbine buffer (3 oz) is the starting point. If you are running a suppressor or an adjustable gas block, a heavier buffer (H, H2, or H3) reduces bolt carrier velocity and cycling aggression. The buffer tube diameter must match the stock you are running — mil-spec and commercial spec are different dimensions.
Lower parts kits: Most LPKs include everything except the trigger, hammer, pistol grip, and buffer system. Quality varies — CMMG and BCM LPKs are what we recommend over budget options. A bad disconnector or plunger spring causes more function problems than most buyers expect.
Trigger installation: Most drop-in cassette triggers (Geissele, Rise, Timney) install without modifications. Standard mil-spec triggers require pinning the trigger and hammer individually. We do trigger installs in-store — call for current labor pricing.


