This is the recipe I use for supersonic loads for my Model 1 300 Blackout Carbine. Over 500 rounds of this recipe fired through my 16″ rifle at distances up to 200 yards to punch paper and plink. I use Berrys 155gr jacketed .308 FMJBT for the projectiles and AA1680 for powder. The bolt locks open after the last round clears.
The reason I didn’t go with a 110 or 135gr projectile is pretty much convenience: I like using Berrys plated pistol bullets for my handgun training ammo and this was the lightest (therefore cheapest) .308 boat-tail they carry. At about $0.22 each (although who knows what price they will come back at after they clear the 6-8 month order backlog) it makes plinking rather affordable with the BLK compared to the luxury factory ammo prices as production ramps up. Based on recent news this wont happen until a few months after the current logjam on ammo production is cleared…
Accurate 1680 is tough to find sometimes but the powder density matches the case capacity very nicely in the BLK. I use CCI primers because they are a bit faster burning than Winchester and that’s handy for subsonic loads. KB ALERT: Winchester or a similar, harder primer are the only safe ones to use in a Lee Progressive loader.
I run this load recipe on my Lee Precision 4-hole Turret Press and load both factory BLK brass and 5.56 brass trimmed to 300BLK specs.
Update: I notices some pressure signs on my brass and have adjusted the starting load to lower the charge. Please update your records accordingly.
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- The standard AR-15 mag accepts cartridges up to 2.260 OAL
- The SAAMI Specs show an acceptable range of 1.78-2.260 OAL for the 300 BLK
- Min OAL: 2.140 to accommodate projectile length