side charging upper for an AR

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5.56 vs. .300 BLK: A Few Things to Know

September 11, 2025
side charging upper for an AR

Two common chamberings for AR-style rifles are 5.56 NATO and a less-common, more modern offshoot, .300 BLK, also referred to as .300 Blackout. Side by side, it is apparent that the .300 BLK shoots a larger, heavier bullet, but if you’re thinking about building with a side charging upper for an AR build and are […]