If you already own a 5.56 AR-15 and you're eyeing 300 Blackout, the real question is what you can keep and what you have to replace. The answer is cleaner than most forum threads make it: your bolt carrier group, lower, buffer, and magazines all carry over. Only the barrel and gas system change. Everything else about a 300 BLK upper is identical to your 5.56 rifle. The short an …
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Buyers ask this exact question before every aftermarket Glock 19 slide purchase: Gen 3, Gen 4, or Gen 5 — what actually fits? The short answer is that Gen 3 slides fit Gen 1 through Gen 3 frames, Gen 4 slides fit Gen 4 frames, Gen 5 slides fit Gen 5 frames, and cross-generation swaps are possible but require the matching recoil spring assembly and sometimes a striker swap …
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Optic footprint mismatches drive more red-dot returns than any other slide question. The cut on your slide and the bolt pattern on your optic have to match — and the terminology is confusing because "RMR cut," "RMSc cut," and "Holosun K" refer to bolt patterns that are not interchangeable. This guide maps each footprint to the Glock platforms 3CR cuts slides for, explains …
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