I have two rifles chambered in .300 BLK. One is a Mod. 700 Remington with a 16" threaded barrel. The other is an AR upper with a 12.5" threaded barrel.

I have a TBAC 30P-1 suppressor I use with both.

Basically I have three loads. One is a supersonic load using the 125 grain Hornady SST ahead of 17.5 grains of WW296 and a CCI400 at an OAL of 2.25". It's accurate and fast.

On the other end of the spectrum I am loading subsonic loads using the 208 grain Hornady A-Max with about 11 grains of H4198 at the same OAL of 2.25". I say "about 11 grains" because this takes a bit of tinkering to keep it subsonic. Many people use heavier bullets for their subsonic loads. I think I chose the 208 A-Max because of its availability at the time. These are accurate and deadly.

The two loads just mentioned are set at the overall length of 2.25" because that is the maximum OAL for the 5.56mm. I'm running them through an AR magazine, so that's the length.

One thing shooters must be very careful about: NEVER INSERT A MAGAZINE OF .300 BLK INTO A 5.56mm AR. The .300 BLK cartridge usually will chamber in the 5.56mm chamber, and the result is KABOOM! The general advice is to segregate magazines used for the .300 BLK and mark them with red tape or something. I have some nylon magazines I use only for the .300 BLK, and I use only aluminum magazines for 5.56mm. You can see one of my nylon magazines in the photo below.

In the middle, I bought some factory remanufactured ammunition loaded with 147 grain FMJ bullets for plinking. These are supersonic and give good accuracy.

I much prefer the 12.5" AR to the bolt rifle. I like the shorter barrel and the AR platform. The suppressor is not ungainly with the shorter barrel. You get the velocity you want with supersonic loads, and it's easier to stay subsonic when you want to.

The U.S.A. has restrictions on short barrels for rifles (16" minimum). That's a pain. I legally use my 12.5" upper on an M16A1, because the govt. doesn't care how long the barrel is on a machinegun. I also use it legally on an AR15 pistol lower. Go figure. I cannot use it legally on my standard Colt AR15 semi-auto lower assembly.

Here it is on the M16A1. I have since changed the scope to a Leupold 1-4 with illuminated dot reticle. You really don't need much magnification with the .300 BLK.

Of course, in Oz all this talk of semi-autos or full-autos is wasted. I assume your only choice will be the bolt action. As I said, mine is a Rem. 700. I never have been a fan of the Rem. 700, so I don't have a lot to say about it. I've only had it to the range a couple of times and probably should sell it. If CZ makes a .300 BLK with a 16" threaded barrel that should be a good choice.

Both of mine have 1:7 twist, which is standard for the .300 BLK.

In summary, I like the .300 BLK very much. It is a versatile cartridge that spans a lot of uses. It's also a lot of fun. Admittedly, I didn't read your long posts above, so if I have been redundant to what was said there, please forgive.

Curl