supersonic 300 BLK recipe: 150gr FMJBT

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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Caliber: 300 AAC Blackout (300 BLK) 
Projectile: 150gr jacketed FMJBT
Primer: CCI Small Rifle Primers (no. 400)
Powder: AA1680
Measure: 18.0 gr starting load
Lee Auto-Disc setting: 1.18
Min OAL: 2.140
Max OAL: see discussion below

Regarding OAL I had to experiment to find a length that fed well. Here is my thought process to arrive at the OAL I set my dies to:
This seems like a pretty big tolerance. I set my seating die to give me the longest possible cartridge-about 2.200. Some factory ammo I purchased didn’t feed well due to FTC (Failure to Chamber). It turned out that they were the short end of the SAAMI OAL specs. Some scouring on forums and experimentation proved that longer OAL fed better : no FTCs on any of my BLK cartridges since this change

Be safe and have fun out there. As you can see I had one flyer at 100m but I’m pretty sure that was just me getting settled. Sorry but its just that fun to use this short range tackdriver and it’s still a group you can be proud of.

2 thoughts on “supersonic 300 BLK recipe: 150gr FMJBT

  1. Pingback: Internet reloading recipes- a cautionary tale | kR-15: info and resources for firearms enthusiasts

  2. Pingback: Chronograph results- at long last | kR-15: info and resources for firearms enthusiasts

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