300 Aac Blackout (300blk)

[rsilvers]

PT&G is selling official 300 BLK reamers and headspace gauges. Forster Products is making official 300 BLK dies.

[robrob]

Looks like a really original idea they came up with. Not.

[robpiat]

Originally Posted by robrob

Looks like a really original idea they came up with. Not.

Merchandising!!!!

[TCCrewchief76]

...and may the Schwartz be with youuuuuuuuueeeeeeeeuuuuuuuuuueeeeeeeeeeeuuuuuuuuuu .....

[Scalce]

Good for them for bringing it to market.

Nobody else submitted the caliber to SAAMI.

I view this as a good thing.

[rsilvers]

If you load your own ammo, pay special attention to all of the normal safety practices. Recommended powder for most supersonic loads is Hodgdon H110.

For subsonic, there are special requirements and nearly all published loads are non-optimal for the 300 BLK upper. Many existing loads were developed for Thompson Center® single-shot pistols, or for ARs by people not aware of the magazine limitations. These loads pay no attention to automatic rifle function and should not be used. Look for a load which results in a cyclic rate of 700 rpm or more. AA1680 is recommended because its bulk density matches the case capacity and it will generate enough gas pressure to cycle the weapon.


Suggested subsonic load:

• R-P 300 AAC BLACKOUT brass
• Remington 7.5 primers
• 11.2 grains of AA 1680 powder
• Case length is 1.368 +0.000 -0.020
• Sierra 220 MK loaded to 2.089 OAL (this length is optimal for reliable feeding from USGI magazines)
• Chamber pressure 21,100 psi.

[alorton]

With a case length of 1.348" to 1.368" it sounds exactly like a 300 Whisper / 300-221 / 300 Fireball with a trim to length of 1.355". I'm assuming since they recommend AA1680 as the subsonic powder that the system uses a carbine length gas tube instead the pistol length. That is unfortunate as the pistol length has proven to be more versatile when switching back and forth between subsonic and supersonic.

As for the magazine problems caused by the bullet diameter that isn't anything new with AR shooters. I've found that a Pmag with the side rib removed is the best solution as opposed to loading ammo to a specific length. This also works well with my 7.62x40 which can't rely on overall length as the case is too long to allow such short loading.

Overall, I don't see anything new here. That said, I think it will be good for the cartridge family to have a SAAMI approved chamber and solid factory backing. I'm still waiting to see if the ammo is interchangable between the Blackout and the Whisper. From what I have read I suspect it may be.

[carcass]

I realize this is a somewhat older thread but I thought I'd ask here.

Originally Posted by rsilvers

Suggested subsonic load:

• R-P 300 AAC BLACKOUT brass
• Remington 7.5 primers
• 11.2 grains of AA 1680 powder
• Case length is 1.368 +0.000 -0.020
• Sierra 220 MK loaded to 2.089 OAL (this length is optimal for reliable feeding from USGI magazines)
• Chamber pressure 21,100 psi.

What barrel length will result in this being subsonic? I have a 7.5" barrel that I chambered for "300 Fireball" or whatever PTG calls their reamer, and I have good reliability with subsonic operation and F/A cycling in an M4 (carbine stock tube with standard recoil buffer) with 9.2 grains of Lilgun, 1.085 OAL, with a chamber pressure of about 33kpsig.

I don't have any 1680 lying around but would like to try this load, but only if it'll work in my short barrel on F/A. BTW, Quickload calculates my load to result in about 8700 psig bore pressure at the gas port position, which is just enough to allow reliable operation. QL calculates your listed load at 8500 psig, but with lower efficiency of powder burn (80% vs 97%). The additional mass of powder (gas) at that lower pressure may provide enough momentum to operate the action. The weird thing is that you state chamber pressure of your load at 21.1kpsig, but QL calculates it at 39kpsig. Any idea what the discrepancy is? Is QL not good at calculating at these relatively small case volumes?

Thanks for any info, and I hope I haven't missed an answer to this that someone already posted.