300 AAC BLACKOUT 12.5 inch = 300 Fireball 16 inch?

[rsilvers]

It is looking like a 12.5 inch 300 AAC BLACKOUT matches the velocity of a 16 inch 300 Fireball. This is probably due to the extra freebore (like 5.56mm compared to 223 or 6.8 SPC-II compared to 6.8 SPC SAAMI).

I was noticing that I could extra grains of powder before signs of pressure in a load that others were using with 18 grains. Previous loads will need to be re-worked up if you have a real 300 AAC BLACKOUT chamber. And remember - don't shoot 300 AAC BLACKOUT ammo in a previous chamber as it will have additional pressure.

[SDB777]

Having a little difficulty following what your trying to communicate to me(us)...

Comparing velocity of two completely different cartridges, with different barrel lengths means pretty much, oh well.....

Barrel #1: 14" 300Whisper
Barrel #2: 24" 300Whisper
I can manipulate the powder charge to make the 14"(#1) out perform the 24"(#2) all day. Even if the powder charge is the same, the projectiles can be manipulated to make #1 look superior....even the seating depth, crimp/no-crimp, number of lands and grooves, twist rate, etc, etc.....

Even two completely indentical cartridges just being chambered in two different barrels(with the same twist rate, lands-n-grooves, length of freebore, length of barrel) can give some very large differences.


Or are you saying that the 300AAC is a better cartridge then the 300Fireball?

Scott

[BWE Firearms]

Well put SDB777. I think barrels are like snowflakes no two are the same. I have seen two barrels by the same manufacturer made at the same time using the same ammo that produce different velocities.

I have two of my 338 THUMPERS one 12" one 16". I have loads that are faster in the 12" then in the 16". They were made from the same blank with the same reamer one right after the other.

rsilvers are you talking about subsonic or supersonic loads? What bullets and what powder are you using? What are the twist rates of the barrels? We need more info.

[rsilvers]

I am saying that if you fix the OAL of two cartridges and load the same bullet - one to be 55,000 PSI in a 300 AAC BLACKOUT chamber and load the other to be 55,000 PSI in a 300 Fireball or Whisper(R) chamber and use the same barrel blank for each, the 300 AAC BLACKOUT will be higher velocity.

So in effect, the 300 AAC BLACKOUT can get 16 inch 300 Fireball performance from a 12.5 inch barrel.

The difference being like comparing 6.8 SPC-II to 6.8 SPC SAMMI.

[Garrett]

Originally Posted by rsilvers

...So in effect, the 300 AAC BLACKOUT can get 16 inch 300 Fireball performance from a 12.5 inch barrel...

Okay. But the whole purpose for the .300 Whisper was to shoot heavy bullets at subsonic velocities. It's neat that the 300 AAC can push bullets faster. So can a .308, .30-06, etc. If I want supersonic bullets, I'll use one of those. If I'm shooting a .300 Whisper, or a 300 AAC Blackout, I'm going to tailor the load to give me between 1000 and 1050 fps, in the barrel I am using, whatever that length might be. The top-end velocities in this type of cartridge are not relevant, as long as they are above the speed of sound.

Don't get me wrong. I like what AAC has done with the new cartridge. I like that it's been submitted to SAAMI to give it the mainstream legitimacy that SSK was never able to generate for the .300W. But to tell us that it can push a bullet faster than the .300W just doesn't impress me. That's not the cartridge's reason for being.

Now if you came out and said for a given powder / bullet / velocity combo, the AAC round produces 20% less noise than the .300W when shooting suppressed, I'd be more interested.

[Mike-Sid]

Originally Posted by rsilvers

I am saying that if you fix the OAL of two cartridges and load the same bullet - one to be 55,000 PSI in a 300 AAC BLACKOUT chamber and load the other to be 55,000 PSI in a 300 Fireball or Whisper(R) chamber and use the same barrel blank for each, the 300 AAC BLACKOUT will be higher velocity.

So in effect, the 300 AAC BLACKOUT can get 16 inch 300 Fireball performance from a 12.5 inch barrel.

The difference being like comparing 6.8 SPC-II to 6.8 SPC SAMMI.

Robert what is the advantage of the 300 AAC blackout over the 300 Whisper? Is the faster velocity the only advantage? I have not really read up on the 300 AAC. I figure you are the one to ask. Thanks

[rsilvers]

The main advantage is that it was submitted to SAAMI so now larger companies can make ammo and guns for it. Aside from that, 300 Fireball and Whisper(TM) can do all the same things as 300 AAC BLACKOUT. But yes, 300 AAC BLACKOUT seems capable of higher velocities for any given pressure limit. By the end of next week I should know more about how much we are talking about.

[snipecatcher]

Originally Posted by rsilvers

It is looking like a 12.5 inch 300 AAC BLACKOUT matches the velocity of a 16 inch 300 Fireball. This is probably due to the extra freebore (like 5.56mm compared to 223 or 6.8 SPC-II compared to 6.8 SPC SAAMI).

I was noticing that I could extra grains of powder before signs of pressure in a load that others were using with 18 grains. Previous loads will need to be re-worked up if you have a real 300 AAC BLACKOUT chamber. And remember - don't shoot 300 AAC BLACKOUT ammo in a previous chamber as it will have additional pressure.

But aren't your recommended seating depths extremely short to function correctly in the AR15 mag? Seated to your recommended OAL, seems like there is a lot of powder space wasted.
-Dan

[rsilvers]

Originally Posted by snipecatcher

But aren't your recommended seating depths extremely short to function correctly in the AR15 mag? Seated to your recommended OAL, seems like there is a lot of powder space wasted.
-Dan

True with longer bullets. But that is optional and applies to 300 Fireball and 300 Whisper also for best feeding. You can load to full SAMMI length of 2.26 if you want to give up some feed reliability in existing mags. We are going to make some custom mags for people who want to shoot long ammo.

[Scalce]

So does the extra freebore that positively affects velocity also negatively affect subsonic accuracy as the bullet needs to jump slightly further to the lands?