A buddy of mine bet me $20 I couldn’t work that into an article on AmmoLand News. Here’s the skinny though… It’s true depending on where you land. The 556mm has a challenger. A real contender. So, when I crack a movie line from “48 Hrs.” as humor, it’s valid. The 300BO may be the sheriff in town for a good many customers.
The 556 has a tremendous volume. Whether this is realized in the form of America’s most popular sporting rifle platform, the AR15, or a myriad of other configurations, you can’t deny the popularity. The 300BO would have a serious hill to climb to best this kind of volume across the globe. But, I don’t live all across the globe. Neither do you. We’re, in most cases, truly interested in what works primarily for ourselves. And if we’re smart, we’re asking ourselves what will each of us do with an intended weapon 90% of the time. When we ask questions like these and answer them adequately, we just might find that the 300BO or the 556 was tailor-made just for us. Let’s explore the possibilities.
In part 1 of the 556 v 300BO series, I offered some perspective on the origins of the 556 and the 300BO. It’s important to know what and why a thing is a thing. For this installment, it is necessary to do a serious comparison. There will be a part 3 of the 556 vs 300BO as well, where they’re tested and run through the paces. For now, we need to illustrate the attributes, weaknesses, and strengths of each and also project how they fit with our intended uses. Each of us is different in this regard, so we’ll try to cover a lot of ground.
Attributes, Weaknesses, & Strengths of 300 BLK vs 5.56
In terms of size, the 556 caliber ammunition round is often found in the 55gr and 62gr weights. Granted, there is plenty above and below, but you’ll see those two grain weights most often. In the case of the 300BO, I typically see the 110gr and the 125gr the most when casually shopping. The same is true of course, in that you’ll find 300BO well below and above the common core.
300 ACC Subsonic
Something interesting is the subsonic offerings in 300BO. I know there are many of you out there that simply don’t care about this hidden gem among characteristics. But, if you’ve ever tried to do any real wet-work or common hunting, even when suppressed, there is a ton of noise associated with pulling the trigger. I can drop a magazine, cycle a round out, hammer another mag home full of subsonic, drop a carrier, and be in the business of quiet as my prerequisites for the transition from noisy to shush. That’s huge in any carbine and not too many chamberings or weapons out there offer this flexibility.
I’ve said it before and I’ll say it again. The AR15 weapon the Stoner team came up with makes this all possible. With most other weapons, this transition in 300BO from super to subsonic is much tougher, more expensive, and takes a lot of time and effort. With something as simple as 1/9 twist in the 556 I’ve stabilized 69gr and a bit over and shot them out to 1000yds. I’m no Camp Perry contender. And even with a ton of elevation dialed in, I could hold MOA or a tad over in most cases. I don’t mean to put across to you that the 556 can’t effectively use plenty of different types of ammunition. With those same barrels I was shooting 1K with heavy FGMM, I’ve also shot 45gr VMAX in a field of prairie dogs out to 700yds. It can be done. Heck, every now and then I actually hit one at that range. 😉 My longest shots were back-to-back pulls of the trigger with 52gr TNTs at 702yds. Two big daddies barked no longer. So, 556 has flexibility.
The 300BO though, has a wider range of flexibility, IF you need it. When can you cycle 78gr 300BO and also 220gr in the same 1/8twist barrel? Dude… That’s insane compared to most chamberings on the market. Make yourself a list of the available bullets on the market you can load and then nearly triple the weight, and see if they still work at all. Oh, and run them through a gas-operated weapon, not a bolt. I’ll bet your list is pretty short.
If you didn’t notice above, I quantified some of what could be done with a quality 556 built weapon, which had solid optics, and an average shooter. There are many riflemen better than me, with far better performance, I assure you. Range isn’t a problem with the 556. You can pretty much do practical things beyond the typical need. For me, in rifle configuration, being defined as 18” or longer, the 556 is the king of the two. I can’t imagine what kind of elevation I’d be dialing in for a 300BO on those 2 prairie dogs I mentioned above. Instead of nearly 10ft of drop with a 52gr sizzler, I’d been at something more like triple that with a 125gr projectile from a 300BO. Even with a canted rail and a ton of available elevation in my scope, I’d been using a holdover for sure. Not good.
300 Blackout Excels at Short Ranges
When it comes to carbine applications things don’t improve in terms of long-distance. But, if we’re talking about SBRs or pistols in the 10.5” category, new possibilities exist depending on your range. If we’re going to avoid long-distance shooting, and concentrate on things as simple as hitting man-size targets at 300yds and closer, it’s a race again. Or at least close enough, you can do the work. The 300BO will arrive a little later due to a lower speed, it’ll hit a bit harder, and smack the target a bit lower. Keep in mind though, when you chop a 556 back to 10.5 you’re killing the velocity, so remember that.
I recall the first time I built a 7.5” AR15 as a test weapon in my shop. I was ringing steel with it and after the first round hit, I was like, “What’s up with this ammo?” There was far less “Thwack” going on. I didn’t notice it as much in 10.5” and 11.5” but it was a quick reflection I’ll never forget.
When you compare what an average 300BO and 556 will do in a short barrel configuration there is a slight nod to the 300BO in terms of power and a slight nod to the 556 in terms of trajectory. But for truly close work, they’re both in it to win it. This translates to hunting game inside those closer distances as well. You’re going to have more forgiveness with a 300BO in most cases than the 556. While I’d use both on a coyote, I’d probably stick to the 300BO for deer-sized game, bear, etc. Depending on elevated shot placement and other factors both would be fine for hogs and the likes.
The Finicky 300BO
Another thing you’ll notice is how finicky the 300BO isn’t in terms of gas system settings. Once you get one dialed in, you’re in pretty good shape regardless of the ammo you choose to run. Even so with short barrels. That isn’t the case with the 556. When barrels get really short, hopping around to various ammo weights and transitioning between suppressed and unsuppressed uses can be a problem. It takes some work to overcome those gas problems. I wish there was a magical formula, and we’ve got our shortlist of things we do to each weapon that falls in that category, but it’s not always as easy as using our cheat sheet.
It’s truly pretty hard to compare these two ammo offerings in an apple to apple heads-up comparison. If you’re going to use these both in barrels that are about a foot long in 300yd circumstances and in, then you’ll only pay a bit more on the average for the 300BO ammo. But if you need a shorter barrel or serious suppression, the 300BO is something to seriously consider. If you’re looking for range and speed, the 556 is a clear winner. You should be asking yourself how you intend on using the weapon 90% of the time. If you can answer that, your choices should come a little easier.
The final part 3 article in this series will surround the actual testing and reflection of each in a 10.5” configuration. That’s where they tend to intersect, so we’ll put them through their paces as such. We’ll find out if the new Reggie Hammond is the real deal or not.
About Michael Ware:
Michael is a Christian husband and father to two children. He owns and operates Controlled Chaos Arms, a premier custom weapons shop in the Midwest. He serves as Chairman of the board of Directors at the Iowa Firearms Coalition. The pursuit of truth drives him in research and his writing.
Michael enjoys shooting, hunting, and fishing throughout the Midwest and Rockies. An avid outdoorsman and tireless supporter of all Second Amendment virtues, he can be found in his gun shop, in a tree stand with his kids, or on Capitol Hill lobbying in support of Freedom and Liberty at any given time.