.300 AAC Blackout - 'Enabling' Thread (Mags, ammo, optics, barrels, etc.)

[OlongJohnson]

As I understand it, it's about the rib that the necks ride on. Because the subsonic bullets are generally longer and fatter, they end up being closer to .308 at the location of the rib, so they get scrunched toward the centerline of the mag. So the .300 BLK mags have shallower ribs to accomodate the larger bullet diameter. The supersonic bullets tend to taper in more and be skinny enough at the location of the rib that they work OK in 5.56 mags. So it's all about bullet shape.

There's probably some aspect of what bullet/what mags/what gun that requires you to test in your gun to be sure.

[Norville]

Fiocchi 150 FMJ on sale at PSA, 49.99 for a box of 50.

Daily Deal section.

https://palmettostatearmory.com/fioc...s-300blkc.html

[OlongJohnson]

All the .300 BLK geeks I've read say that 150 is the range to stay away from. Not subsonic, but takes up too much case volume to get good velocity and energy as a super, so it's performance is disproportionately worse than stuff in the 110-125gr range. But if you really need to shoot and that's all you can get, it probably goes bang OK.

[BobinNC]

In the last month starline has had 300 blk brass available on backorder. I placed an order about 3 weeks ago and it shipped out today. I have a decent amount of brass, and obviously you can convert most 5.56/223 brass, but I have some 110 barnes and 200 Makers that I wanted to load, and figured I would try to get some new brass to load them up with.

If you can wait a bit, anytime they have the backorder open, you should get brass fairly quickly.

Yes, Starline delivers quite quickly on backorders. I've never waited longer than 3 weeks, even at the height of the shortages. I've got about 750 cases on hand.

One thing I should note if you've never used Starline 300 Blk brass before, it's heavy. Almost 11.2 grains on average heavier than Hornady brass for example. I reduced max and min Hornady load data by 1.3 grains and worked up with this brass.

My current super load is:

110 gr. VMax or 110 gr. Nosler Varmaggeddon
19.4 grains Lil'Gun (Max looks like 19.7 grains in my AR15) but why push it.
Starline Brass
CCI 450 Primer.
2.070" COAL

[OlongJohnson]

Tac-TX 110 components in stock: https://www.centerfireguns.com/barne...-50-30321.html

[SLUZENE]

BCM now does a 7" 1:7 300blk upper
https://bravocompanyusa.com/bcm-stan...r-5-handguard/

[Maca]

I am astonished at the accuracy of a short barreled 300BO AR15.

This is from my 8.25" V7 rifle at 50 yards, rested with an Aimpoint T2 with Magtech ammo.

[nate89]

Yes, Starline delivers quite quickly on backorders. I've never waited longer than 3 weeks, even at the height of the shortages. I've got about 750 cases on hand.

One thing I should note if you've never used Starline 300 Blk brass before, it's heavy. Almost 11.2 grains on average heavier than Hornady brass for example. I reduced max and min Hornady load data by 1.3 grains and worked up with this brass.

My current super load is:

110 gr. VMax or 110 gr. Nosler Varmaggeddon
19.4 grains Lil'Gun (Max looks like 19.7 grains in my AR15) but why push it.
Starline Brass
CCI 450 Primer.
2.070" COAL

I use H110, but similar results for me. A buddy of mine did some supers testing with a magnetospeed, and you can feel when the recoil really starts going up, and the brass starts showing that you are pushing it. No reason to add .5 grains for almost no benefit velocity-wise.

[nate89]

BCM now does a 7" 1:7 300blk upper
https://bravocompanyusa.com/bcm-stan...r-5-handguard/

Interesting, I wanted to see the barrel profile, but they don't sell it alone yet. Funny thing I had a BCM 9" barrel cut down years ago to 7.25" and I still use it for supers. It was one of the only chrome-lined blackout barrels around. Even cutting the barrel down it is still capable of amazing accuracy with nosler 110 varmagedons with 19.5 grains of H110.

[SLUZENE]

Interesting, I wanted to see the barrel profile, but they don't sell it alone yet. Funny thing I had a BCM 9" barrel cut down years ago to 7.25" and I still use it for supers. It was one of the only chrome-lined blackout barrels around. Even cutting the barrel down it is still capable of amazing accuracy with nosler 110 varmagedons with 19.5 grains of H110.

Same. It does appear to have some sort of continuous taper, but how heavy? Why no MK2 upper? I wonder if there's plans for a 1:5" twist to compete directly with the Sig/Daniel Defense offerings.

RECCE-7 (300 BLK)
BCM® 300 Blackout Upper Receiver Groups

Continuous taper barrel profile designed for optimal weight, balance, and performance.

Tapered barrel profile out front, for easier maneuverability.

No sharp handguard cap shoulder for improved barrel harmonics and improved accuracy.

Muzzle threaded in standard 30 cal (5/8x24).

Includes MCMR-5 Handguard

Includes MCMR-SM (MCMR Sling Mount)

Includes One 3" Picatinny Rail Section

Includes 7.62/300BLK Flash Hider


BCM® has taken great care to ensure the best possible performance and interchangeability. However, due to the large operational range of 300 Blackout ammunition in the market place, BCM® cannot guarantee function will all ammunition types in all conditions. These barrels were designed to run with a carbine buffer with subsonic ammo and a H3 buffer with high velocity ammo. Fine tuning may be required in limited instances based on ammo and buffer choices that work best for the desired application. BCM® also recommends running the Crane O-ring (provided with all BCM® Bolt Carrier Groups) over the extractor with 300 Blackout.


Caliber: 300 Blackout
Barrel Length: 7"
Barrel Material: 11595E Spec Steel
Barrel Finish: Manganese Phosphate (Mil-Spec A-A-59267)
Bore & Chamber: Chrome Lined
Weight: 2.2 lbs
Twist Rate: 1:7
Gas System: Pistol
Muzzle Device: 762/300BLK Flash Hider
Muzzle Threads: 5/8x24
Handguard: MCMR-5