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View Full Version : For Things That Go Bump in the Night- Suppressed 300 Blackout SBR Custom Build



RobertTheTexan
01-13-18, 03:08
ETA: FYI, if you are using Tapatalk and are not seeing my parts list, Tapatalk is cutting out 3/4ths of my post and I have no idea why. If you are seeing the parts list, then it’s just messed up on my end...

A few of you guys that know me know about my "Rule of Commonality". It means my firearms will be in common calibers. Up until this build that has been 9mm, 5.56 and 7.62x51. All NATO rounds. All ammo in abundance. But after finally getting my AAC 762 SDN-6 can, the idea of having an SBR with the potential for really quiet operation became very appealing to me. Realizing the range limitations of subsonic 300 ammo, I still felt that I had a solid purpose for a weapon of this type in my defense plan. It's kind of crazy how I ended up with a BA Premium 8" 300BLK barrel, but it sort of magically morphed into that from a 16" Faxon Gunner 300BLK. That story for another time.

I also wanted to build this AR - as much as possible with existing parts, some of them used on my other builds, that I've broken down or were on AR's I no longer shot. From a price-point - this is a budget build. From a parts perspective, IMO, it is as good as any AR I've built.

Total out of pocket to get this SBR operational: $206. I had to pick up a 7" LaRue Tactical rail (thanks docsherm) and a AAC 51T Blackout 5/8x24 from Lanbo's Armory
Upper:

Upper Receiver: I believe this is an upper I picked up from AAC. It has a Mueller Industries forge mark on it. I had a few in my spare parts. They are either Aero, Colt, Vltor MUR-1A, or AAC. This definitely is not the Colt or Vltor and Aero usually has an "A" forge mark.
Barrel: Ballistic Advantage Premium 8" 300 Blackout: It's no secret these are some of my favorite barrels. My longer BA barrels are both subMOA barrels -very accurate. My other SBR barrels shoot as well as my Daniel Defense barrels. For the money, you're hard pressed to beat them.
BCG: LMT L7D3 (FA) BCG - Because I pretty much only use LMT L7D3's or their enhanced bolt carrier (L7Q3A) with standard LMT bolt. I believe they are are tough as nails and as well made as a BCG can be.
Charging Handle: Radian Raptor - formerly know as the Artist AXTS Raptor.
Gas Block: CMT JAG gas block (non-adjustable) with BA melonite pistol length gas tube
Muzzle Device: AAC Blackout 5/8 x 24 Muzzle Brake
Handguards: LaRue Tactical 7" rail. Because LaRue Tactical rails are the best quad rail in the world. [emoji4]
BUIS: Daniel Defense (I like to run Precision Reflex fixed sights, but these are what I had on hand.)
Optic: EOTech EXPS-3

Lower:
Lower Receiver: Aero Precision standard stripped lower - They work
LPK: DSG Arms with DSG billet trigger guard, mag catch button, Radian Talon Short-Throw Ambi Safety Selector
Trigger: CMC 3.5 SS trigger. Its what I had on hand
Buffer System: Vltor A5 using an H0 buffer and Sprinco Green Spring
Buttstock: Magpul SL-S stock. These are growing on me and I had one on hand.
Pistol Grip: Hogue Overmolded w/ Beavertail

Addition Components:
- TRL-1S WML
- Troy Ambi Bolt Catch
- Boonie Packer Redi-Mag
- BCM Mod 3 Vertical Grip
- BFG VCAS padded sling

This SBR has a dedicated can - an AAC 762 SDN-6 (.30 cal can). Not that I have a lot to compare it to, but so far I'm very pleased with its performance. As an aside, my POI shift isn't as bad as I thought it would be.(This comment more geared towards when I shot my precision AR's with this can.) Since receiving this can (after waiting 547 days) I've bought another of the same, which is slated for my 308 precision AR.

Range time: Test fired suppressed and unsuppressed. Test fired 208gr and 220gr subsonic and 120gr super sonic ammo. Initially I was using an H2 buffer with the Green Spring, but the BCG would not lock back on empty mag while shooting unsuppressed subsonic ammo. I swapped out the H2 for a lighter H0 and the weapon worked as advertised - both unsuppressed subs, to suppressed supersonic. It runs flawlessly.
I mitigated gas blow-back by lining the horseshoe of the Raptor CH with black high temp RTV. (Thanks docsherm)

I zeroed it at 100 yds. At 100 yards the subsonic ammo doesn't have any drop. I'm able to hit my 8" consistently, and 6" plates 7/10.
I also was able to hit 8" plates and 3/10 hits on my 6" plate at 200 yards, but I had to use a magnifier. But I was pleased with that also.

Today at the PD range, at a distance of 50 yards, I was able to run some 5x5x5 drills that required running to each firing position, shooting into paper plates at 50m. I scored 15 hits all three iterations, under a timer in 24 seconds. I'm not saying that's bad or that's good. I think it's OK. A funny thing, was that we didn't get a good time until my last run because the can was too quiet and my LEO friend could't figure out why his timer wasn't working. With this setup, the barrel rise was almost unnoticeable, and I was able to squeeze off the 5 rounds pretty quickly.

So bottom line up front - I'm very, very happy with the build. I believe it will fill the purpose for which it was built perfectly. Once I got the right buffer in it, she ran like the proverbial top and I have experienced zero malfunctions. It is a better CQB rifle than I anticipated, because my follow-on shots are much faster and my groupings are very tight. The HD ammo I use (Hornady Black 208gr Subsonic) peels back like an onion and would create a rather large wound channel/cavity. So it fits that purpose for me perfectly, plus on top being much more quiet than my 9mm and especially a 5.56.

Pics:
https://s20.postimg.org/aphy8a01p/79_BEA788-2387-4_C47-8434-7_B7_CBF6_BA0_F9.jpg

https://s20.postimg.org/bf0qkng0t/0_F48_C9_A2-_B395-4192-_AD8_C-2_AD8_CD02_F78_B.jpg

https://s20.postimg.org/lay6x0tzh/B87_D7420-_A30_E-4_FDE-_B938-_DBEDA410_C2_D7.jpg

https://s20.postimg.org/4aohg1drx/5_CB5_D98_B-818_B-49_BE-95_C3-0371_D756_B2_B9.jpg

Not my best job, but it works.
https://s20.postimg.org/m0gz9ck8d/AB489384-333_C-4_C03-9836-_BB29674_BE299.jpg

nksmfamjp
01-13-18, 06:42
Very nice. Did you forget to stake your buffer tube nut?

Also, for me, that trigger pull is a bit light for a fighting gun.....I would look at the POF 4.5 or ra140

RobertTheTexan
01-13-18, 08:19
Very nice. Did you forget to stake your buffer tube nut?

Also, for me, that trigger pull is a bit light for a fighting gun.....I would look at the POF 4.5 or ra140

Thanks nksmfamjp.

I agree. My usual go-to trigger is a 4.5lb EDT2. After trying more than a few triggers, I chose the EDT2 as a replacement for all the lighter triggers I had initially installed. I have about 3 installed and about 3-4 triggers to go. I just don’t have any spare EDT2’s.



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officerX
01-13-18, 09:34
Very nice! It’s very similar to my HD setup.

http://i1195.photobucket.com/albums/aa393/officerfrasher/F49C5FFA-0DEC-4E02-9AED-19463036C93C_zpsy5hwycmj.jpg

wigbones
01-13-18, 10:28
Great looking build! How do you like the BCM vertical grip? I've been contemplating picking one up for a little while now or sticking with another Magpul RVG.

fedupflyer
01-13-18, 10:43
I am also in the final phases of my suppressed 300 Blkout SBR.
The only thing I question in the Eotech for HD.
As much as I prefer the Eotech recticle ( I have about 4 of them) I would seriously consider an Aimpoint for HD use and only due to the battery life.

I put a Hyperfire EDT2 trigger in mine, so far it works great.

I am using a BCM assembled upper and they suggest using the H3 buffer with a standard carbine spring. So far that works great but I have yet to shoot it suppressed.

RobertTheTexan
01-13-18, 11:27
Great looking build! How do you like the BCM vertical grip? I've been contemplating picking one up for a little while now or sticking with another Magpul RVG.

Thanks bro. I use a modified C clamp on my fore-end and so the angled Mod 3 really fits my hand perfectly for that grip. I’ve tried other stubbies, Tango Doen, Fortis, Magpul, and they are OK, but hands down the Mod 3 is my favorite.




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RobertTheTexan
01-13-18, 11:38
I am also in the final phases of my suppressed 300 Blkout SBR.
The only thing I question in the Eotech for HD.
As much as I prefer the Eotech recticle ( I have about 4 of them) I would seriously consider an Aimpoint for HD use and only due to the battery life.

I put a Hyperfire EDT2 trigger in mine, so far it works great.

I am using a BCM assembled upper and they suggest using the H3 buffer with a standard carbine spring. So far that works great but I have yet to shoot it suppressed.

My first go-to for HD is my G19, so if I have to get it out, I have time to hit the button. I have a CompM4s and it’s a great optic, but for CQB, IMO there’s not a better optic than the EOTech, and so that’s what drove my optic choice.
Sounds like you’ve got a really nice 300 SBR. I had a spare A5 system and didn’t see that many applicationsx most were carbine buffer systems, but thought it should work fine and it really does. I’m not sure how much it affects recoil as compared to my 5.56 SBR’s but I can tell you that you can sling lead pretty fast and keep a pretty small shot group. Again that could be true of a carbine system - I don’t have a reference. But I definitely like how it runs..

Are you waiting for a stamp on a can or haven’t gotten that far along?




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VARIABLE9
01-13-18, 11:38
Nice indeed!

wigbones
01-13-18, 13:31
Thanks bro. I use a modified C clamp on my fore-end and so the angled Mod 3 really fits my hand perfectly for that grip. I’ve tried other stubbies, Tango Doen, Fortis, Magpul, and they are OK, but hands down the Mod 3 is my favorite.




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I'll have to give one a shot and see how it compares. Thanks for the input. Have fun shooting!

fedupflyer
01-13-18, 20:32
Are you waiting for a stamp on a can or haven’t gotten that far along?


No, I have all of the tax stamps and the suppressor in hand.
I am just doing a break in with chicken bones, fairy farts and tears of a virgin liberal.

Work and weather have gotten in the way of playing with my toys and I was trying to run the upper fairly hard before I start monkey with it. Think I might have about 100 rnds through it now.
Once I am satisfied with it overall ability I am gonna run some accuracy test at 100yds to see what it will do, then I will swap the current muzzle device for the dead air keymod and see how much I disturbed the accuracy.
Once that is done, I plan on running it in at least two 3-Gun outlaw style matches so that I can verify it runs like it is supposed to with the suppressor attached.
Then I can accept it as a HD gun.

Not OCD at all.

Diamondback
01-13-18, 21:06
No, I have all of the tax stamps and the suppressor in hand.
I am just doing a break in with chicken bones, fairy farts and tears of a virgin liberal.
There are still a few of those around? O.O

Nice build, RTT! Just out of curiosity, does subsonic .300 get any benefit from a longer barrel? I'm toying with the idea of Blackout spare URG's for the 10.3" pistol I'm building and a 12.5" I'm penciling out...

You guys make me jealous, living in free places where you can actually USE magazines in your range testing, unlike my little slice of Fuddtard Hell. :(

officerX
01-13-18, 21:29
There are still a few of those around? O.O

Nice build, RTT! Just out of curiosity, does subsonic .300 get any benefit from a longer barrel? I'm toying with the idea of Blackout spare URG's for the 10.3" pistol I'm building and a 12.5" I'm penciling out...

You guys make me jealous, living in free places where you can actually USE magazines in your range testing, unlike my little slice of Fuddtard Hell. :(

From my research 9” is the sweet spot. Which is why AAC made one that length, and why I bought it!

RobertTheTexan
01-13-18, 21:33
There are still a few of those around? O.O

Nice build, RTT! Just out of curiosity, does subsonic .300 get any benefit from a longer barrel? I'm toying with the idea of Blackout spare URG's for the 10.3" pistol I'm building and a 12.5" I'm penciling out...

You guys make me jealous, living in free places where you can actually USE magazines in your range testing, unlike my little slice of Fuddtard Hell. :(

I may be wrong, but I believe a 9” barrel achieves close to full powder burn with subsonic 300. So if you’re wondering if there’s better accuracy to be had with a barrel longer than that, maybe, but I don’t think so. But I may be wrong. What I know is that the 300 subs’ sweet spot is a 100 yds and less. So at 100 yards I can hit my 8” plate all day. I get 75% hits on my 6” plate. If I bring that in to 50yd as I did today, I don’t really need to hold over, it was pretty dialed in all the way to 25 yds. Now if you step out to 200, your looking at around a foot or so of drop, 250-300 it climbs up to about 35”-39” of drop. Could you still do some damage? I suppose but it reminds me of lobbing 40mm grenades out of a M203 launcher. I haven’t measured the bullet drop of my subs out to 200 and 250, but those numbers are consistent with the research I’ve done. Supers are a different story as you already know.
Pack your grip, load granny in her rocker on top of the truck and move to a free state.


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RobertTheTexan
01-13-18, 21:41
There are still a few of those around? O.O

Nice build, RTT! Just out of curiosity, does subsonic .300 get any benefit from a longer barrel? I'm toying with the idea of Blackout spare URG's for the 10.3" pistol I'm building and a 12.5" I'm penciling out...

You guys make me jealous, living in free places where you can actually USE magazines in your range testing, unlike my little slice of Fuddtard Hell. :(

You’ll find a lot of guys also running 7.5” and like me 8” barrels on the 300. Guys that KNOW stuff. That leads me to believe that there just isn’t a lot of accuracy to be gained from 7.5” to 9” or 8” to 9” especially at 100 and less with subsonic ammo. But if I’m smokin crack on that - someone just tell me. OfficerX is correct, AAC would know since they gave birth to the 300BLK.


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Iraqgunz
01-14-18, 02:12
I'd be staking the castle nut/endplate if it were me.