Convert Model 12 .223 to .300 Blackout

[TXCOONDOG]

I have a Model 12 in .223 SS and kicking around the idea of converting it to .300 Blackout (barrel swap) or buying a dedicated BA for subsonic loads and cast bullets.

Any thoughts?

[Dave Hoback]

Not my thing as 223 outperforms 300 blackwhisper. And I’m not a fan of subsonic anything. Subsonic means slow! And slow means horrible ballistics. I don’t even do any AR’s in it. But in a bolt gun makes even less sense IMO.

However, that’s just me. If it interests you go for it! If you don’t like it, only cost you a barrel.

[KMW1954]

Too bad you are so far away or I would offer a swap with a nice Model 10 223 that is ready for a barrel swap.

[Hdskip]

Not to rob your thread or change your mind but I am in the process of changing my model 10 to a 30/223. I have already accomplished this in an AR platform. Due to magazine restraints I'm limited to short flat or round nosed bullets.....This will work much better in a bolt gun. To accomplish this I rechambered a 300 B/O barrel to 30/223. As with most of my projects it may make little sense to others. I did it because i just plain wanted to. ��. Ill report on this as it progresses in a new thread. Any way best of luck on your project.

[Dave Hoback]

Not to rob your thread or change your mind but I am in the process of changing my model 10 to a 30/223. I have already accomplished this in an AR platform. Due to magazine restraints I'm limited to short flat or round nosed bullets.....This will work much better in a bolt gun. To accomplish this I rechambered a 300 B/O barrel to 30/223. As with most of my projects it may make little sense to others. I did it because i just plain wanted to. ��. Ill report on this as it progresses in a new thread. Any way best of luck on your project.

So…. You basically have a 30 Carbine? Ya know… study kinda sucked, right? LOL! Serious though… you’re running the 110gr 30cal RN pills, I’m guessing?

[charlie b]

Sounds like the .30 Ham'r. What the BO should have been if they were not after subsonic.

[Dave Hoback]

Sounds like the .30 Ham'r. What the BO should have been if they were not after subsonic.

He said he can only use the Round Nose or Flat bullets. So it’s more like this below, in the middle.. or as I said, the 30 Carbine.

https://i.ibb.co/6X65HvD/4-D677398-C615-4408-8-C3-A-52-F26102-B044.jpg (https://imgbb.com/)

[hamiltonkiler]

I’d load the .223 with trail boss before I messed around with the 30cal. But I can a .44 or 45/70 sub sonic as the bullet size and the new offerings that expand under 1000fps


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[Dave Hoback]

I don’t understand this relatively new interest in Sub-sonic ammunition. I remember 15 years ago, if you wanted Sub, you went 22LR, some 9mm & 45ACP because that’s were it naturally performed! But now there’s all this buzz… using heavy, high BC bullets in teeny-weeny cases. I don’t understand what they are for? Can’t imagine for hunting. These bullets don’t perform correctly under set velocities. I think a whole lotta people need to actually study the ballistics more. A modern ballistic tip designed to be fired at say 2800muzzle, does not perform at Sub velocity. The Tip is not driven into the bullet, opening up the nose & causing the energy dump! (Like it should.) No. They typically just pass through the target, causing a caliber size wound channel. They aren’t for long range because they lack that altogether. I just don’t get it.

Many years ago, I watched a documentary on Hypersonic guns. Not the newer generation of “cannons”, so to speak. These are laboratory stationary machines, which are huge! I remember a 50-70 foot long barrel! They fired a projectile as small as a single grain sand in some cases, at around 50K FPS. Not a typo.. no. That was 50,000FPS+. I can’t remember the energy, but they explained it in if a person were hit by one of these objects, they would almost be vaporized! This is when I was going through my AR15 SBR phase, and had just started reloading… 2008 I think. That was the preverbal end to my SBR fascination.

[charlie b]

Subsonic is big in some areas. Don't want a lot of noise to upset the neighbors. I've always had some subsonic loads for my regular rifles when out hunting. Could harvest squirrel or rabbit without spooking the rest of the game animals for miles around. My .308 shoots cast subsonic bullets within 1 1/2" at 100yd. Even the Garand does well with them, although it becomes a single shot.

The BO was expressly intended for subsonic and suppressed loads. The larger bullet was considered 'optimum' for down range performance with the low muzzle vel while still fitting in the AR mag using the same bolt face. It was for military use, mainly special ops stuff. Kind of a fall back after the .458 SOCOM failed to gain much headway.

For the OP. If interested in cast loads there are really a couple ways to proceed depending on what you want from it. Subsonic requires very little powder so the BO is a decent choice. Many AR folks don't like cast out of the BO, but, they are trying to balance a gas system as well. If you want a little faster, then the .30BR is a favorite of cast bullet target shooters. Get one with a slower twist (1:10 or even 1:14). But, brass is expensive and a bit harder to come by. At this point you can make a case for the .30 Ham'r or .30/.223 as you would not have to change the bolt.

I've not been a fan of the .30 carbine for rifles because of it's headspacing. Makes a good 'pistol' caliber carbine.

[Dave Hoback]

Ok… yeah. I can see the whole noise thing I guess. I’m just not convinced that’s the ever pressing issue for the majority of folk with the Sub-Bug.:rolleyes:


The 30 Carbine was an utter failure from start to finish & for every facet of shooting. Every time I see someone going nuts over an M1 Carbine(who isn’t expressly a collector), all I can do is put my head in hands and think, “DOH!”

[charlie b]

The little carbine was a great concept for what it was. Kinda like a .357mag. A 110gn bullet at 1900fps isn't anything to sneeze at. Remember it was the replacement for a pistol, not a rifle. It performed well, even in more stressing situations. Some troops preferred it over a pistol or Garand for house clearing.