I never really understood the hype behind the .300 Blackout cartridge. Basically, a blown-out 5.56 that would cycle through an AR platform and throw heavy bullets in the subsonic realm.
Now, I see that they have come out with the 8.6 Blackout. Based on the 6.5 Creedmoor case, it throws a .338 bullet in the subsonic realm. From the article:
Another advantage of the 8.6 BLK has nothing to do with the cartridge at all, but everything to do with the barrel. Unlike .300 BLK and 338 ARC ammunition, which are designed to work with a rifling-twist rate of 1:8-inch, the 8.6 BLK uses a rifling-twist rate of 1:3-inch. This is an incredibly fast twist rate, but what’s it for? Well, it helps better stabilize bullets that are about the size of your little finger, but it also significantly enhances terminal performance.
A 1:3 twist? I understand that this isn't a cast bullet cartridge, but I've done work with cast bullets that won't stand a fast twist.
RPM = MV X 720/Twist Rate
So, let's plug inn some numbers. If that bullet is going 800 fps down that barrel, it will be twisting at 192,000 rpm. If that is what it takes to stabilize a long bullet, then that is what it takes, but I'm wondering what the fouling is going to look like.
I don't get it. I just don't see the utility. But then again, I'm an old Fudd. I have my rifle. But, I hope they sell those things by the carload. The more people in the shooting sports, the better.
2 comments:
I've personally never understood the penchant for trying to make the AR platform do things that it was never designed or intended to do.
It's a great platform and I've got several rifles of that type, but it's got its limitations...primarily the short cartridge length.
I get the desire to have a more powerful loading, but that's why I also have an AR-10 platform rifle. And a lever gun. And several bolt action rifles.
They each have their benefits and their limitations. Seems to me that frankensteining up a cartridge to try to duplicate a capability already achieved in another platform is a bit silly.
Let the AR be good at what it's good at. If you need something else...buy something else.
You can always use another gun right?
Everything is a balancing act. A faster rifling twist will help a harder bullet penetrate straighter. It will also make a softer bullet mushroom more and sooner, limiting penetration. Every bullet, whether pure lead or machined from solid bronze, has a maximum rpm and will disintegrate if spun faster. At longer distances a faster spin will keep the nose up more, surfing through the air, causing the bullet to impact more sideways than point first.
One advantage to subsonic ammo with heavy bullets is lower noise. Find a cheap break action.45-70 with a long barrel and make ammo with 500gr soft cast bullets ahead of 5 or so grains of bullseye, red dot, or unique. It’s nearly silent, goes a little bit faster than a.45 Colt with twice the bullet weight. This is one time when you do want a faster twist barrel, say 1:10 vs the normal 1:20, to keep the bullet stable out to 100 yards or so, but now we’re talking a custom built rifle $$$$.
Post a Comment