Need some help starting / finishing a 300 AAC BLK build.

[FatedFrenzy]

Hey guys and girls. To start, this isn't my first AR build, but it is my first chambered in the 300 AAC BLK. I know many people just take an existing AR and swap the barrel or the entire upper, but I wanted to build a rifle from the ground up designed specifically for this round. I'll start my listing what I have planned so far to give you all the info, and then ask my questions based on that. I should also note that I live in NY so an SBR is IMPOSSIBLE.

Barrel - 14.5", Melonite, 1:8, Pistol Length Gas
Muzzle Device - Undecided
Receiver Set - Aero Precision ASO Lim. Ed. M5 (FDE)
Trigger Group - RRA 2 stage
MOE Rifle Stock (FDE)
MOE Grip (FDE)
Rail - Fortis Switch 14" (FDE)
BCG - AIM BCG-X

I'm obviously looking to have as few problems as possible right from the start. Will any 5.56 low-pro gas block (.750) work well with a 300 BLK pistol length gas system or should I be looking at something specific? Is there anything else I should know that I wouldn't be unaware of only building 5.56 rifles previously? Primary uses will be 300 yards and under, though I can see me trying to push it further on targets. I'm open to any and all suggestions. Thanks people!

[SomeOtherGuy]

I should also note that I live in NY so an SBR is IMPOSSIBLE.

Barrel - 14.5", Melonite, 1:8, Pistol Length Gas
Muzzle Device - Undecided
***
Primary uses will be 300 yards and under, though I can see me trying to push it further on targets. I'm open to any and all suggestions. Thanks people!

Unless I missed a recent change, NY also does not allow suppressors. With no SBR and no suppressor, I can't see much point in 300 Blackout. That's coming from an early-adopting owner, btw. The supersonic performance is not so great - not as good as 7.62x39 within 300 yards (and very marginally better at greater distances if you use a high BC bullet), not as good as 6.8 SPC at any distance, and debatable vs. lowly old 5.56. It was advertised as being the equal of 7.62x39 and nipping at the heels of 6.8, but no load released to commercial sales is there, nor have I read of any super secret squirrel loads that are. (With a short barrel and a can, things are quite different and 300BLK has some benefits.)

If you still want a 300BLK, I'd be looking at a 16" barrel with a plain muzzle (due to NY law banning threaded muzzles unless a brake is permanently attached) and a carbine gas system. Or you could do a 14.5" with a 1.5"+ brake permanently attached, but 300BLK doesn't have lots of recoil and you would probably be better off with the extra muzzle velocity, lower cost and ability to use a carbine gas system on a 16" barrel. (A 14.5" may require pistol length gas - outside of my expertise.)

[MWL]

Ditch the RRA 2 Stage trigger group. Too many reports from experienced users that indicate that they become problematic at around 1000 rounds, some less. Spend your money on a Geissele or something with a similar reputation.

Regards.

Mark

[FatedFrenzy]

Then 300 BLK might not be what I'm looking for then. I keep getting mixed reviews. I know that it was designed as a short(er) range round that worked well suppressed, but I've heard of people utilizing it up to 1000 yards (on targets). I really just wanted to build another AR, and this time I wanted to mix it up. I already have 3 chambered in 5.56 (I know many people have more) but I couldn't justify spending the money to build another in the same caliber. I guess what I really wanted was something that had about the stopping power of a .308, while not needing the full range of a .308, and bypassing the cost of building an AR-10.

I've read good things about the 6.8 SPC but could benefit from learning more. Does it really have enough stopping power compared to the 5.56 to justify a complete new build? 300 win mag (drool) is just too far out of my price range right now and really probably until I pay off my student loans; so when I'm like 80. may just suck it up and build a .308. I have been really digging the SI-Defense .308 ambi-set.

I have heard mixed reviews about the RRA 2 stage. I'm looking for something better than standard, but I don't need match grade. I may check out the POF drop-in or Stag has a new 2 Stage. I may have just got lucky and gotten a good one, but the single stage in my Stag when building my SPR is awesome. Just a slight bit of grittiness on take up i could live without, but when not paying attention, you don't notice it.

But please, continue to chime in on the 300 BLK questions I originally had, I'm not fully decided on ending the project.

[SomeOtherGuy]

Then 300 BLK might not be what I'm looking for then. I keep getting mixed reviews. I know that it was designed as a short(er) range round that worked well suppressed, but I've heard of people utilizing it up to 1000 yards (on targets). I really just wanted to build another AR, and this time I wanted to mix it up. I already have 3 chambered in 5.56 (I know many people have more) but I couldn't justify spending the money to build another in the same caliber. I guess what I really wanted was something that had about the stopping power of a .308, while not needing the full range of a .308, and bypassing the cost of building an AR-10.

I've read good things about the 6.8 SPC but could benefit from learning more. Does it really have enough stopping power compared to the 5.56 to justify a complete new build? 300 win mag (drool) is just too far out of my price range right now and really probably until I pay off my student loans; so when I'm like 80. may just suck it up and build a .308. I have been really digging the SI-Defense .308 ambi-set.

Contrary to some aging tropes, people hit with .224 bullets don't tend to keep coming, especially at close distances. M193 is not ideal and M855 isn't either, but you aren't a GI and you can use better ammo for self defense. Lots of different 5.56 loads will stop bad guys at any plausible self-defense range. I don't see any stopping power issue with 5.56 against bad guy humans. Against large bears (literally, Ursus ___) you want a .30-06 or larger, with .308 Win in a pinch.

One guy, one time, did a trick video of shooting steel at 1k yards with a 300BLK. It's not practical. Somewhere between howitzer and mortar style shooting. No use in the real world.

I bought into 300BLK for reasons that I hadn't clearly outlined for myself prior to buying - similar to what you're describing - and it's brought me no benefit. I see 300BLK as being useful in three very specific situations:

1) You want maximum range for subsonic ammo with a suppressor - it's a good option.
2) You are going to run an SBR or AR pistol and want something that retains good velocity in a short barrel - it's a good option.
3) You are hunting a moderately sized game animal (whitetail deer, for example) in a state that doesn't allow .224 bullets to be used and you really, really, really want to use an AR15 - it's an OK choice (but 6.8 or 6.5 might be better).

In hindsight I would have been better off putting together a high precision 20" upper in 5.56 for precision target shooting, something I actually do.


I have heard mixed reviews about the RRA 2 stage. I'm looking for something better than standard, but I don't need match grade. I may check out the POF drop-in or Stag has a new 2 Stage. I may have just got lucky and gotten a good one, but the single stage in my Stag when building my SPR is awesome. Just a slight bit of grittiness on take up i could live without, but when not paying attention, you don't notice it.

The relatively new Ruger two-stage AR trigger is getting good reviews and runs around $125 or so. You may also be able to find a Geissele G2S, or the older but similar S2S, for that same price range. I had a RRA briefly (in an RRA rifle) and wasn't impressed with its feel compared to Geissele.

If you don't need it to be a two stage, the Hiperfire EDT is a nice somewhat-better-than-GI trigger for $85. I've been using one for several months and have found no faults yet, and will probably be buying another.

[FatedFrenzy]

I have no arguments with you, despite what some will say, with 5.56 taking down a man just fine, in fact I have first hand knowledge of M193 working great on whitetail if placed in the neck or chest cavity (<300yards). This build is A, to build something different for me, and B, might as well make it something with some more power for something bigger than a whitetail.

Sure, I can use my late 40's Winchester Model '94 chambered in 30-30, or my WWII Mauser K98 chambered in 8mm, or a number of the other rifles and shotguns I own, but you know, as an enthusiast, you can't help but want more options. The more I read about 6.8 the more I think it might be a viable choice. What are people's thoughts on the 6.8 spc? I've heard there are a few variants of the ammo, unlike 300 BLK which is all the same.

Trigger doesn't have to be 2 stage, I actually don't have a 2 stage in any of my rifles. I kind of wanted to build this rifle different in every way I've built an AR before. Wanted to think outside of MY own proverbial box if you will.

[Rayrevolver]

Another option is the 6.5 Grendel, if you are looking for more long range action.

That said, I agree with the above guys about 300BLK not making sense in anything other than a suppressed SBR, unless its a hunting minimum thing. Even then, the 6.8 SPC is a better option.

ALL THAT SAID, the nice thing about 300BLK is you do not need to invest in wacky magazines and BCGs, just a new barrel.

PS - Assuming you are not a millionaire, all these rounds are much more expensive to shoot than .223/5.56. My advice, either build a different 5.56 (lightweight 18"???), or spend the money on a 2 day carbine class at Blackwater.

[FatedFrenzy]

One nice thing about NY is that we can hunt with .223/5.56. The 6.5 is nice but I'm not looking to get into anything proprietary, otherwise I'd probably build a 50 Beowulf just for the fun of it. I'm well aware of the price difference in ammo, and one of the reasons part of me is leaning toward .308 as this is the next least expensive round and obviously readily available even at WalMart.

I already have a very lightweight 5.56. I think if I were to build another in that cal, I'd build an M16A1 replica.

[Slvr Surfr]

The 6.8SPC is a great alternative. There are plenty of ammo choices. 85gr - 120gr rounds. The only issue you may deal with is the fact that nothing in the 6.8SPC AR world is mil-spec, kind of like the .308 platform. Meaning your build may have some teething issues. The main components that are different are the barrel, bolt, and magazine. It is a good intermediate round in between the 5.56 and .308, good for varmint up to light/medium size game.



Here is all you ever wanted to know about the 6.8SPC platform.

http://www.68forums.com/forums/

[Gunnar da Wolf]

I hunt standard sized whitetail deer in the area behind my house with other houses @ 1/2 mile away. After shooting a friend's suppressed .300BO I decided to build one with the understanding that it's not a powerful rifle cartridge. I'm amused by the 6.8 users who are appalled that anyone actually likes the 300BO. No it's not as powerful, yes it will work for what it's designed to do, shoot heavy bullets subsonic and shoot light bullets supersonic. From the same gun, without adjusting anything.

I used a 16" DD barrel and various other parts to create pretty much a standard free floated carbine and I've been rewarded by 1" groups at 100 yards with Hornady's 125gr SST at 2,200fps, better than 1" with 110gr VMAX at 2,400fps and 100% reliability. I bought 1,000 pieces of converted LC brass for $100 delivered. It sips W296 powder at 17.5gr per shot with the 125's. I'll eventually buy a suppressor but until then it's a fun little gun to shoot.

I have two coworkers who have Rock River 6.8 rifles and they are very pleased with them, the .300BO is just easier to start out with requiring only a barrel a set of dies and some pistol powder.

[fledge]

Have you looked at 277 wolverine? Also just a barrel swap from the 556 platform.

[epwrangler]

I just bought a $100 barrel and put an upper together. It shoots pretty well with UMC 120grn supersonic. I am looking to find something similar to reload.

Sent from my SM-G925T using Tapatalk

[Joelski]

I'm' in the process of stamping a canned 10.5" sbr with intention of sticking as close to the mk18 spec (sans duct tape) as possible. The bump in caliber will be consolation for the lack of the tater switch. If there's already a spec in place for such an abomination, please point me that way.

I know it neither is, nor can be a real mk18 clone without being 100% true to the spec. Close and boomy is good enough to put the smile on my face.

[FatedFrenzy]

Well, after much deliberation, and talking to my brother about his 300 (he get's sub-MOA groups with 125gr Hornady hand loads out of a 16" DD barrel), I've decided to continue with the 300 BLK build. I wanted to build something "beyond 5.56", that didn't cost more to build, that has readily available ammo by multiple manufacturers, and I can comfortably hunt all game within NY (the largest being black bear typically no larger than 200lbs).

For those who are interested, the build list is as follows:

Receiver Set: Aero Precision (Cerakote burnt bronze)
Barrel: MAS Defense 14.5" mid-weight melonite 1:8, pistol length gas
Rail: Fortis REV II 14" (Cerakote burnt bronze)
Stock: MOE Rifle Stock
BCG: AIM Surplus BCG-X
Muzzle Device: Spikes Barking Spider II
Optic: Vortex Strike Eagle

[Rayrevolver]

You are spending a lot of money on that wacky Barking Spider muzzle device. Instead of a $165 barrel and $135 muzzle device, you would be better served with a $300 barrel. Or a $200 barrel and $100 towards a trigger.

And the 300BLK with pistol gas does need any more back pressure from that 9.4oz Barking Spider.

And since SBRs are verboten in NY you must be building a 14.5" pistol? If not a pistol, why not a 16" with any other muzzle device that doesn't weigh close to 10oz and then need to be pinned/welded?

Now you have to spend money to remove that muzzle device when you get sick of all the weight and no return like a suppressor.

Good luck.

[Tx_Aggie]

You are spending a lot of money on that wacky Barking Spider muzzle device. Instead of a $165 barrel and $135 muzzle device, you would be better served with a $300 barrel. Or a $200 barrel and $100 towards a trigger.

And the 300BLK with pistol gas does need any more back pressure from that 9.4oz Barking Spider.

And since SBRs are verboten in NY you must be building a 14.5" pistol? If not a pistol, why not a 16" with any other muzzle device that doesn't weigh close to 10oz and then need to be pinned/welded?

Now you have to spend money to remove that muzzle device when you get sick of all the weight and no return like a suppressor.

Good luck.

I completely agree with this. No need for a back pressure muzzle device on a 300 blackout. That money would serve you better if spent on the barrel or trigger. I'd also suggest looking at Ballistic Advantage or maybe one of the Rainier Arms select barrels. The RA barrel is Stainless with 5r rifling and almost certainly outshoot the MAS Defense barrel you have listed above. It's priced at about $260 and can be had in an ion bonded black finish if you don't like bare stainless.

[FatedFrenzy]

Well, I went with MAS Defense because of their reputation and cost. I can't find anything but great reviews on their product and customer service, not to mention their price, as a newer company is enticing. I don't need it to be match grade as will this round I'm not planning on shooting past 300y. And most likely not past 100y.

I went with 14.5 and a 14" rail to have that fully covered look. I'm not solid on the muzzle device, as. I really just liked the look of it and really like how my SPR shoots with a linear comp on it.

Again, not building a match rifle, I was PLANNING on going with a Stag Arms trigger group as I get sub-moa with my SPR with that trigger shooting XM193. I also put one in my CQB, replacing the sloppy Anderson one I originally put in it. I have been happy with both of them.

You did bring up a valid point that I did not consider which is the weight of the muzzle device. I will most likely reconsider and use something else.