I’ve been drinking the 300 BLK Kool Aid for a while now, and one of the reasons is that even though the factory fresh ammo is scarce I can cook up as much as I want from old 5.56 brass and readily available components. I’ve recently had a number of people ask me for my particular recipe (the combination of components and powder weights that make my load), and I figured it would be a good idea to put that into article form so I can talk a little about why I chose the components I did and how I got to my current load.
First things first: a standard disclaimer. Reloading ammunition is an inherently risky activity. This load works for me, but I CANNOT guarantee that this load won’t blow up your gun and/or kill you. I highly suggest you start with a lower load and work your way up as you become comfortable. Use this load at your own risk.
Enough stalling, here’s the recipe:
| Powder | Hogdon H110 |
| Primer | CCI #400 |
| Bullet Type | Hornady FMJ BT |
| Bullet Wt | 150 gr |
| Powder Wt | 16.5 gr |
| COL | 2.260 in |
Experienced loaders will notice that I’m using a pistol powder for a rifle load. Which, normally, is a big no-no as pistol powders burn much too fast. But since there’s really almost no case volume left in the 5.56 case once you cram a GIGANTIC .308 bullet in the top (of a case that you trimmed down, no less), fast burning powders are the only option.
The other interesting choice on the list is the CCI #400 primers. CCI makes a primer specifically for 5.56 ammunition called the CCI Small Rifle Military Primers #41, and the reason for the difference is that the primers are a little stiffer. The floating firing pin in the AR-15 rifle makes it possible to have a slam fire situation under the right conditions, and stiffer primers reduce that probability. That said, I’m on my third 1,000 count box of #400 primers and not so much as a single slam fire has occurred with either 5.56 or 300 BLK loads. Plus they’re cheaper, and so am I.
Let’s talk about powder weight.
The max load on a 300 Whisper load (from what I remember, don’t quote me) for 150 grain projectiles is somewhere around 18 grains of H110. At 18 grains everything starts to wear out quicker and the load becomes dangerous. There’s no real good load data for 300 BLK yet for the bullet weights I’m using, so since 300 Whisper is a lower pressure load one assumes it to be safe to use interchangeably. So, being the cautious guy I am, I started my load at 11 grains of H110. 11 grains is sufficient to cycle the action. Most of the time.
Yeah, that’s embarrassing. But with a silencer and the added back pressure it works damn near 100% of the time. Plus, the light charge makes the recoil as gentle as the morning breeze and keeps the wear and tear on the parts to a minimum. A fine “farting around on the range” load.
The only issue is with the lethality of these rounds for hunting. While the bullet will probably do the job at that relatively low velocity, I wanted something that was faster and with more energy for better expansion and a more humane kill. So I slowly worked up the scale until I hit 16.5 grains, which is high enough to give me a good velocity yet low enough to give me wiggle room for the cheap crappy powder thrower to screw up and still be below the max load. Not that I’ve ever had that problem, but I don’t like taking chances.
Despite my concern for the powder thrower being a POC, as it turns out these are some of the most consistent loads I’ve ever made. With an average velocity of 1,942 feet per second (within 100 FPS of factory loads), I get an IQR of 16 for these loads. For comparison, the most consistent factory load I’ve tested is somewhere around 20. Consistently zippy rounds are the key to accurate and humane kills, and these results are exactly what I like to see.
Which brings me to the reason I chose 150 grain bullets. The standard factory loading for supersonic 300 BLK is a 115 gr round, but there are a ton more options available at the 150 gr mark. Not only are there tons of cheap FMJ or SP rounds available from Hornaday and Remington, but there are also a wide variety of bullets specifically designed for hunting. Like the SST or GMX from Hornaday. Or the TSX / TTSX rounds from Barnes. And because they’re all the same weight, they can be used more or less interchangeably. Practice with the crappy cheap bullets, hunt with the good ones. After you’ve chronographed both and compared the ballistic profiles, that is.
The great thing about handloading your own ammo is that you can tailor your load to your application. Since this gun is primarily a hunting firearm, a quick yet consistent load is what I wanted. But if I wanted this as a competition gun, a lighter load would lead to faster follow-up shots while still making the power factor. In short, your mileage may vary. But for me, I like this load.