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

[Flamingo]

I just bought an 8" 300 BLK upper from Ballistic Advantage. I am waiting on my ASR flashhider.

I was lucky enough to buy several thousand rounds prior to the great panic. I don't know why but I think I want to put a LPVO on it. I have an early DD 300 BO carbine, but it has a carbine length gas system and it is way over gassed. I get a bunch of gas-to-the-face when I shoot it with the can on it.

[Trigger]

So... I jumped into the .300 BLK game at pretty much the worst possible time.
Good energy out of a short barrel led me to order an Aero 8 inch upper a couple weeks ago for what I thought was a reasonable price ($400).
Then decided to build a complete AR pistol, so ordered a lower from PSA, a CH from Geissele (to match my other AR platforms), and back-order a nitride-coated Wilson Combat BCG from Optics Planet (we’ll see how that works out, as I’ve been pretty frustrated with Optics Planet back-orders in the past).
So got some 147 gr FMJ from TargetSports by acting quickly, but missed out on the Barnes 110 gr TAC-TX last week.
Then just decided to spend what was required to get an adequate supply of the Barnes 110 TAC-TX from this place:
https://www.laxammo.com/rifle/barnes...s-21548-detail
Ordering 80 rds, with shipping and tax, works out to $2.80 per rnd. That’s more than twice what I’ve ever paid for any cartridge.
There were 360-some boxes available yesterday, and just over 100 when I made my order. Which is why I bit the bullet, so to speak. There’s a few left for those of you who are desperate.

I tried the 147 gr ammo, along with some 115 grain solid copper bullets through the 8” 300 upper with my Geissele lower last week.
The 147s were fine, but the 115s were more blasty and unpleasant than any 5.56 out of the 11.5” upper I’d been using. Recoil was also more significant with the 115 gr ammo.

The Geissele Lower has a “Super 42” spring and an H3 buffer, so I don’t know what would mellow it out any more.
The PSA lower that’s on the way to me has a standard carbine buffer.
Any suggestions on changing spring and buffer in the new lower? Geissele apparently doesn’t recommend the super 42 spring with the H1, H2, or H3 buffer for subsonic 300 Blackout.
I don’t have any specific plans to use subsonic, but if it would decrease the blast for indoor shooting, it might be appealing for home defense. And I may look at a can for the 300 BLK once my 5.56 can gets approved.
So...
Any recommendations for:
- spring and buffer combos for my application
- whether it makes any sense to supress supersonic 300 Barnes ammo
- good, SHORT cans for 300 BLK

@Trigger

Gyro, good job! I will say it can be a challenge to get 300BLK to run reliably with both supers and subs. A quality upper with the right gas port, system length, buffer and spring are important. I think you are on the right track with buffer weight and springs, given that you cannot vary the gas with an adjustable gas block. I cannot tell you the magic combination, and since I’m on the road, I can’t tell you what works on my AAC 9” upper.

Supers and subs - I will say both my AAC and the 8” MCX run with both supers and subs. Reloading gives the added advantage to tuning the load to make adequate gas to run the action. H110 will drive subsonic bullets, but will not generate adequate gas compared to AA1680 or CFE BLK. H110 works better for supers. 110-125gr bullets at 2200-2300 FPS seem to work well in ARs, and 180-220gr subs can be made to function reliably. I think I use around 11gr of 1680/CFE to drive 220gr sierras. I think it makes perfect sense to suppress the supers. My favorite super load uses Hornady 110 Vmax / Nosler 110 at 2250fps, driven by H110. It seems to burn most of the powder in the short barrel, and does not produce the fireball and concussion like a 10” 556 does. It is suppressed, but still has a supersonic crack.

Cans - I love the TBAC cans, and recommend the Ultra7 for 300BLK SBRs. That said, most 30 cans are fine, because the BLK does not produce a lot of gas, so the can does not have a challenge like it would with 300 Win Mag. 20gr of powder vs 75. Since I shoot lots of bolt guns, the TBAC works well on both. If you go full auto, the Ultra is a Ti can, and does not hold up as well as a can with an inconel or stainless blast baffle like the Dominus or others. But they can get pricey. Ultra5 would be nice for only 300BLK. But I like a little more versatility, and have an ultra7 and 9.

Due to the current insanity, getting into 300BLK is difficult as you have seen. If you can wait until you can scrounge some reloading components in the next few months at moderate prices, you should be able to get the ammo built your 300 likes. For brass, I do not recommend trying to make your own from 556 brass. Expensive and a pain. Places like https://www.carolinabrass.net/apps/webstore/ would sell converted brass for $100-150 per 500. During the insanity I do not know how that will change, but give it a few months.

[Corse]

I used whatever the AAC manual said and my upper works with both subs and supers.

Copied from AAC MANUAL

ACTION SPRING/BUFFER
Use either the standard USGI M4 or the HK 416 spring. For buffers, select a 4.6 oz (130 gm) H2 or an HK-416 buffer- though a 5.5 oz (155 gm) H3 buffer may be a good choice if you don’t intend to shoot subsonic without a sound suppressor or typically shoot supersonic ammo. Do not use a solid 9mm buffer as it may cause bolt bounce.

[GyroF-16]

I used whatever the AAC manual said and my upper works with both subs and supers.

Copied from AAC MANUAL

ACTION SPRING/BUFFER
Use either the standard USGI M4 or the HK 416 spring. For buffers, select a 4.6 oz (130 gm) H2 or an HK-416 buffer- though a 5.5 oz (155 gm) H3 buffer may be a good choice if you don’t intend to shoot subsonic without a sound suppressor or typically shoot supersonic ammo. Do not use a solid 9mm buffer as it may cause bolt bounce.

Thanks!
Sounds like I’m in the hunt for an H3 buffer, then.

[tango-papa]

I just bought an 8" 300 BLK upper from Ballistic Advantage. I am waiting on my ASR flashhider.

I was lucky enough to buy several thousand rounds prior to the great panic. I don't know why but I think I want to put a LPVO on it. I have an early DD 300 BO carbine, but it has a carbine length gas system and it is way over gassed. I get a bunch of gas-to-the-face when I shoot it with the can on it.

Suggest look at Black River Tactical.
Specifically, the CustomTUNE Gas Port.
The BRT gas port insert is legit and works exactly as advertised.

http://blackrivertactical.com/WP/Adj...Drive-c6464009

[GyroF-16]

Gyro, good job! I will say it can be a challenge to get 300BLK to run reliably with both supers and subs. A quality upper with the right gas port, system length, buffer and spring are important. I think you are on the right track with buffer weight and springs, given that you cannot vary the gas with an adjustable gas block. I cannot tell you the magic combination, and since I’m on the road, I can’t tell you what works on my AAC 9” upper.

Supers and subs - I will say both my AAC and the 8” MCX run with both supers and subs. Reloading gives the added advantage to tuning the load to make adequate gas to run the action. H110 will drive subsonic bullets, but will not generate adequate gas compared to AA1680 or CFE BLK. H110 works better for supers. 110-125gr bullets at 2200-2300 FPS seem to work well in ARs, and 180-220gr subs can be made to function reliably. I think I use around 11gr of 1680/CFE to drive 220gr sierras. I think it makes perfect sense to suppress the supers. My favorite super load uses Hornady 110 Vmax / Nosler 110 at 2250fps, driven by H110. It seems to burn most of the powder in the short barrel, and does not produce the fireball and concussion like a 10” 556 does. It is suppressed, but still has a supersonic crack.

Cans - I love the TBAC cans, and recommend the Ultra7 for 300BLK SBRs. That said, most 30 cans are fine, because the BLK does not produce a lot of gas, so the can does not have a challenge like it would with 300 Win Mag. 20gr of powder vs 75. Since I shoot lots of bolt guns, the TBAC works well on both. If you go full auto, the Ultra is a Ti can, and does not hold up as well as a can with an inconel or stainless blast baffle like the Dominus or others. But they can get pricey. Ultra5 would be nice for only 300BLK. But I like a little more versatility, and have an ultra7 and 9.

Due to the current insanity, getting into 300BLK is difficult as you have seen. If you can wait until you can scrounge some reloading components in the next few months at moderate prices, you should be able to get the ammo built your 300 likes. For brass, I do not recommend trying to make your own from 556 brass. Expensive and a pain. Places like https://www.carolinabrass.net/apps/webstore/ would sell converted brass for $100-150 per 500. During the insanity I do not know how that will change, but give it a few months.

Thanks @Trigger - this is good stuff.

[GyroF-16]

I’ve contacted Aero Precision for their recommendations for spring and buffer for the 8” .300 BLK upper.

Since shooting it with 115 gr supers was quite “violent” feeling (both recoil and blast) using a Geissele H3 w/ Super 42 spring, and a LAW folder (adding extra mass to the BCG), I’m pretty sure I’ll want a good, heavy H3 buffer in the new lower. I’m thinking an Aero H3 buffer (weighs 5.6 oz vs the Geissele 5.4 oz), and also considering a Springco spring with more resistance than standard carbine.

Anyone have recommendations on where to start? Probably try first with standard spring, then maybe move up to Springco Red?
My intent is to make it as soft-shooting and controllable with 110-115 gs supers, while keeping it reliable.

If it helps, here are the gas specs for the Aero 8” upper:
Gas Block: .750
Gas Port: .109
Gas System Length: Pistol

[Trigger]

Saw this label in the man cave. This is the latest supersonic 300BLK I loaded. I think I found 500 Nosler 110 Varmageddon last summer. Using Lil Gun powder.

[GyroF-16]

I’ve contacted Aero Precision for their recommendations for spring and buffer for the 8” .300 BLK upper.

Since shooting it with 115 gr supers was quite “violent” feeling (both recoil and blast) using a Geissele H3 w/ Super 42 spring, and a LAW folder (adding extra mass to the BCG), I’m pretty sure I’ll want a good, heavy H3 buffer in the new lower. I’m thinking an Aero H3 buffer (weighs 5.6 oz vs the Geissele 5.4 oz), and also considering a Springco spring with more resistance than standard carbine.

Anyone have recommendations on where to start? Probably try first with standard spring, then maybe move up to Springco Red?
My intent is to make it as soft-shooting and controllable with 110-115 gs supers, while keeping it reliable.

If it helps, here are the gas specs for the Aero 8” upper:
Gas Block: .750
Gas Port: .109
Gas System Length: Pistol

Aero Precision replied, and told me that an H2 or H3 buffer should work in that upper for supersonic loads (I had specifically mentioned Barnes 110 gr TAC-TX in my request for info), but that I should “evaluate it first.”

So not much help from Aero.

[Norm]

Ammo.com has Black Hills 110 gr TTSX ($41 per box) and 125 gr OTM ($40 per box) in stock currently for those that are still looking...