Spoiler alert: not very much is different. Second spoiler: enough to cause a major weapons malfunction if you get it wrong. Confused enough already?
Since 1992 the .300 Whisper round had been gaining momentum among gun communities primarily for its ability to be loaded to subsonic or supersonic capabilities. When fired with a suppressor the subsonic round provides a hard hitting round with great penetration power that doesn’t kill your eardrums.
Inspired by the success and popularity of the .300 Whisper, the Advanced Armament Corporation developed the .300 Blackout in 2009. Which now brings us to the question at hand. Namely, what in the world is the difference between the two and can I fire both from the same weapon without having it blow in my face?
Building your own weapon has been more popular than ever and AR-parts kits are flying off the shelves faster than the industry can keep up. Yet, questions like these need to be answered so that liberty loving citizens can pew responsibly and safely
.300 Whisper versus .300 Blackout
Even to the naked eye it is hard to tell the difference between these two rounds. The .300 Blackout does have a slightly longer neck on the cartridge, but you would still have as much trouble telling the two apart as you would .223 and a 5.56. For all practical purposes, the ballistics are pretty much the same.
If you are the type of shooter who wants to know every difference of feet per second or ounce of muzzle energy there are tons of ballistic tables out there for you to consume.
But since not everyone has time for that I’m just here to tell that both the .300 Whisper and .300 Blackout go pew pew pew pretty much the same. If that’s good enough for you that’s good enough for me.
The .300 Blackout is a popular AR build because it offers the ability to fire both hypersonic and subsonic rounds with enough power to deliver a hard hit in an upclose fight.
With the .300 Blackout upper becoming as popular as it is this has led many to wonder if they could fire their .300 Whisper rounds out of the same platform. So the answer is a loose yes as the rounds are virtually identical, but you need to take into account the wildcat variable first.
The Wildcat Variable
The .300 Whisper is what is known as a wildcat cartridge in that there is no set or published standard like the Sporting Arms and Manufacturers’ Institute (SAAMI) standard round would have. Meaning not every .300 Whisper is alike and if you come across one of the older rounds that might have been loaded by your uncle Cletus in his garage.
Without set specifications there could be issues where the .300 Whisper creates excessive chamber pressures not supported by the .300 Blackout platform. You can find out everything you need to know about the 300 Blackout platform here.
How do you know if you are wrong? You’ll know it when the barrel blows up in your face. That being said, most commercially loaded .300 Whisper rounds are good to go for the .300 Blackout.
Or if you have a personally loaded round that is less than the maximum load for a .300 Blackout. If you are sorting through Uncle Cletus’ garage and come across a box of .300 Whispers we’d recommend you pass or talk to your local gunsmith.
Keep in mind, every so called “expert” on the internet is far from an actual expert.
So there you have it. The difference between the .300 Whisper and the .300 Blackout is that there is no difference to the easy going shooter.
Both go pew and do exactly what they were intended to do much the same. Just watch out for those personally loaded rounds and stick to commercially loaded options or least those rounds from an uncle you can trust to get it right.