Pick the wrong gas system length for your barrel and the rifle either short-strokes (won't cycle) or over-pressures (battering the bolt). This guide matches gas length to barrel length so you buy an upper and handguard that actually run together — no assembly walk-through, just what fits. The Four Gas System Lengths The "gas system length" is the distance from the chamber …
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If you bought a free-float handguard and then discovered it didn't come with an installation tool — or that the barrel nut doesn't work with your current upper — you've encountered one of the most confusing but easily solved problems in AR-15 building. This article covers the mechanical side: what barrel nut types exist, how they differ, what you need to install ea …
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Glock magazines interchange more than most platforms — but only within the right caliber and frame family, and only in one direction. Here's exactly which Glock mags fit which Glocks. The Two Rules That Govern Everything Caliber must match the magazine body. 9mm and .40 S&W magazines are not interchangeable — the feed lips and body width differ. Bigger frame ma …
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