Long ago I was at the range and one of the regulars was talking about how he had loaded some .300 Whisper rounds and that they were so super quiet. Everyone was so excited to hear them, that it was suppose to be like shooting a silenced rifle. I was working as a range officer at the time so we arranged for the line to be called hot just for this guy so we could hear him shoot.
A shot was fired. I was so very disappointed because it sounded like any other gunshot.
.300 Whisper was changed slightly, and became the .300 AAC Blackout. Robert Silvers did some brilliant marketing and made it popular.
I have heard and read some really outlandish claims about the .300 BLK. Had someone tell me it makes .308 obsolete. I’ve seen many claims online that a suppressed subsonic .300 is hollywood quiet. I’ve even seen more than one person proclaim that the U.S. Military needs to replace all the rifles, carbines, machine guns, and sniper rifles with .300 Blackout. Claims like that made me even more skeptical about the round.
A more realistic comparison is 7.62×39 Russian or .30-30 Winchester. Both are good rounds, but I don’t see anyone clamoring for the U.S. Military to switch to either of them. .300 BLK does have the advantage of using a wider variety of bullet weights than either of those two other cartridges.
For someone plinking unsuppressed, 7.62×39 is far more available and cheaper. .30-30 has more than proven it self over the years.
It seems to me the best strength of the .300 Blackout is out of short barrels. You can have a subgun sized weapon with better performance than a pistol caliber.
An overlooked plus of the .30 cal bore for special operations would be that the barrel would drain quickly when exiting water. Unlike the issues with capillary action keeping water in a 5.56 bore.
Subsonic .300 BLK provides muzzle energy similar to a .45 ACP. Subsonic .300 BLK is more like a pistol cartridge than a rifle round. But it retains the greater flash and blast of a rifle. With the really short barrels and super sonic ammo, you are talking similar performance to an M1 Carbine firing .30 carbine.
I often see the comment of a short barreled AR15 in .300 BLK as a replacement for the MP5. That makes sense as the MP5 is old, large, heavy, has a worse manual of arms. But if you are looking for the smallest package, a SMG with the mag in the grip would be even smaller than an AR15 style weapon.
I don’t really see the appeal. Certainly not a bad round, but what is the real niche of it?