San Tan Tactical STT-15 Billet Lower Receiver

$286

Standard AR-15 lower for all five calibers. 7.62x39 steel mags can bind or fail to lock back in some magwells; an enhanced bolt catch or specific mag brand may be needed. .450 BM uses dedicated straight-wall mags that fit a standard magwell.

Build with this part

Opens the builder with this part fitted. Other parts change only if they have to.

Pros and cons

Pros

Ambi bolt and mag releases installed
Tension screw and enlarged beveled magwell
QD sling slots on both sides

Cons

Expensive
Left mag release sticks out and can snag

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