Home Forums Hunting & Shooting AR and Tactical Rifles New AR15 Build Advice

Looking at putting together my first custom build in 5.56. I have a threaded Aero Precision receiver set, trigger, parts kit, buffer tube, stock and grip so far. I'm planning on getting a standard 16" length barrel with a mid length gas setup. I'm also going to get a standard weight BCG.

With that said, does anyone have advice on gas block and buffer spring? If I have a 16" barrel and a min length gas setup, is it even worth messing with a variable gas block and alternative size spring combination? Excuse my ignorance as I've never fine tuned such a rifle.

Just for simplicity reasons, if the mid length gas setup takes care of any over gas, I would prefer to just do a basic low profile has block. If I went that route, what spring would you go with? Do any of these questions depend on choice of ammo. I was thinking of using fairly standard load 75 grain rounds if it matters.

I was planning on this weapon being for closer quarters out to around 200 yards urban sniping missions. Thanks in advance for any thoughts.

An adjustable GB is great if you plan to run a can. Superlative makes one that vents forward, essentially diverting the gas rather that blocking it. Less likely for the GB to carbon up. If using a adjustable GB you can try a Taccom buffer, light weight. I am using one in a pistol 300 Blk. Works well. You have to use a adjustable GB with the Taccom.

You mentioned a "standard weight BCG". By "standard", do you mean a commercial, or M-16 profile BCG?

Two most important parts are the barrel and BCG.

What's you budget for each?

As for your 200 yard limit, a properly set up 16" carbine that's good for 200 will be good to 500.

At this point in time, I'm not planning on using a can. As far as the BCG, right now I am looking at a Toolcraft M16 compatible nickel boron with 158 carpenter steel. When I said standard weight, I was really referring to the fact that I was not looking at one of the units marketed as a lightweight BCG.

How much were you looking to invest into the barrel?

The barrel you choose will answer all your other questions. I guess I should say the gas port size they drill will determine if it's over gassed or not. Mid length does not guarantee softer shooting.

But a heavier buffer/spring combo will help if it's over gassed. An adjustable gas block just lets you do it easier I guess.

I don't have experience with many mid length barrels but Noveske, Faxon and LaRue are all over gassed compared to Sionics.

A 16" mid-length gas barrel should have a gas port size of .078-.081", as a reference point.

Buy a barrel from a reputable source & likely you will be OK with a standard, non-adjustable gas block & either a Sprinco Blue or a JP spring..............both are very slightly enhanced power rated springs.

Here's a source for both those springs:

No Kick Spring & Buffers

And likely an H(1) buffer.

Every mid-length barrel that I have with a non-adjustable GB runs that setup just fine with ammo from standard 223 to 5.56 Nato.

Worst case, you conceivably might need an H2 weight buffer, highly doubtful you would ever need a carbine weight buffer w/o an adjustable GB.

I strongly suggest that you buy a chrome lined barrel from BCM, FN or Criterion................all 3 are very consistent on gassing & more than accurate enough for your use. BCM has a standard grade & a hammer forged grade.............both shoot fine, IME.

Good Luck.

MM

Lots of solid advise here.

For our ARs we run the stronger green Sprinco rifle spring and need 0.083 port on a mid gas 16 inch for all weather reliability.

I think the pendulum has swung a bit to under gassed for some brands and high altitude/ cold weather/dirty guns need enough gas to drive a strong feed spring.

OP seems a bit worried about overgassed but keep in mind undergassed means the AR won't function.

A bit overgassed means gun runs even when dirty/cold/high altitude.

I've had very good experiences with Criterion barrels.

If I was building a new urban combat AR carbine today, this is the barrel I'd order:

https://criterionbarrels.com/products/ar-15/ar-15-core-series-mid-length-gas/

For a pistol, I'd look at their 11.5" carbine gas:

https://criterionbarrels.com/products/ar-15/ar-15-core-series-carbine-gas/

I'm also very impressed with the FN barrels I have. For Cold Hammer Forged AR barrels, they would be at the top of my list.

As for BCM, they earned their reputation. I needed to upgrade some BGC, so I have a new BCM complete BGC and an additional complete Bolt on the way.

Not really worried about over gases from a recoil standpoint. The gun's gonna have near zero kick anyway. Just trying to wrap my head around making sure the gun is efficient, good for follow up shots, reliable cycling, while keeping things as simple as possible. Probably the same thing everyone wants 😀

Jake,

None of us here are really worried about over gassed from a recoil perspective. Over gassing a gun is unnecessarily hard on the gun. No reason to wear parts out prematurely, especially if these tools are needed for (heaven forbid) urban combat missions. Additionally, it's not so much about felt recoil, as a smoooooth system, one with a minimal amount and violence of movement withing the system. This greatly aids in maintaining a steady muzzle and minimizing split times on follow up shots.

If you want to see what I mean, start with a standard A2 bird cage muzzle device. Go shoot some targets offhand for time.

Then replace it with one of these:

https://www.primaryarms.com/vg6-precision-epsilon-compensator-1-2x28-epsilon556

And see what happens to your times.

While you're at it, run the same experiment off the sand bags, and see what happens to your muzzle dance between shots.

However, keep in mind, that the AR gas system is a SYSTEM. Any change, such as changing the muzzle device can necessitate other changes. As an example, if you system is properly balanced with an A2 bird cage and a Springco Blue spring and H1 or H2 buffer, with the improved break it's likely you will be back to standard carbine buffer and spring.

Good stuff AS. That epsilon vg6 compensator does great things. The only guy that damned near shot as well and fast as I did in the last ar comp was using one. He uses that comp on all of his AR builds and highly recommends them. I've shot his ar's and they perform very well. The only reason mine are faster on target is because I use 20" tubes with rifle length gas systems. I also use captured spring systems like the armaspec stealth recoil system. Rifle length with a 20" tube shoots smooth and soft. Meaning fast on target. If I were using a 16 or 18" barrel, I'd definitely be using an epsilon vg6 and I'd be searching for a mid length gas system barrel vs the carbine length gas system. Also John Burns hits on some good points about reliability. A slightly over gassed rifle is more reliable, but overgassed means its harder on the rifle itself. There's a fine line between the 2. I've shot some factory guns that are way overgassed, like Ruger AR's. They do that so the rifle functions reliably. Some people don't even know their rifles are "over gassed"...

I was actually looking at that Epsilon muzzle device. Seems to have great reviews. What do guys think about the Black hole rifles barrels?

Yes, the line is fine, & the only real way you can get to the optimum gassing level is with the use of an adjustable GB, which the OP has said that he does not want to use.

W/o an AGB, all else is some level of a compromise & one should always, always err to the side of reliability, which by default means to the bias of being (to some level) overgassed.

End of story, all else is fantasy & BS.

And while different muzzle devices affect muzzle jump & apparent perceived recoil, they do not affect the spring or buffer being used.

MM

I haven't ruled out an adjustable gas block. Was just saying that there is value in keeping things simple if the added value is minimal. I also have a growing parts box for an AR10 build that's on my radar. It has a SLR Rifleworks AGB that I could use for this if I choose to do the AR15 first.

On the Epsilon muzzle device, how long is it? Could you make it permanent and go with a 14.5" barrel? Would you?

For what you are doing, you really don't NEED the AGB, but they work great if you're into that level of performance...............most of my guns have them, but the ones that don't work just fine.

The advantage to the AGB is really seen if you want to regularly shoot a wide range of pressure ammo & want the gun optimized for each type or if you want to use or if you want to use a low mass BCG & light weight buffer & those are fine tuning elements not needed for your described use, right now.

Unless you want to go that route.

As for the Epsilon brake..............VG Precision has a website that will give you all the info. I use their Gamma version as it's more compact & IME, more effective, but louder.

Yes, you can pin it on, so long as the finished length is >16".

MM

I have three. They are great barrels, providing the quality has stayed the same since they were bought out by Columbia River Arms. All 3 of mine are pre-merger barrels. They look absolutely beautiful through a bore scope.

They are accurate barrels capable of the high accuracy standards set in this forum, i.e. 10 shot sub MOA groups, or very close to it.

They are stainless barrels, (416R). They have poly rifling, and best I can tell, they use a cut type rifling type process, perhaps it's a broach cut process. But they are not cold hammer forged (CHF), and not button cut, and can vary their process to any twist, so, that only leaves one option....

Their AR barrels are not hand lapped (they will hand lap their bolt barrels for you), and they are not chrome lines. Typically, 416R stainless AR barrels have a shorter life then 4150 CHF barrels. Some would argue this is offset by the use of P3 poly rifling, but I haven't seen any head-to-head data good enough to convince me one way or the other, but if I had to bet, under hard use, I'd put my money on the barrel life of the tier one, CHF chrome line barrels such as the FN's and BCM.

Criterion started as an offshoot from Krieger, when Krieger couldn't make cut rifle barrels fast enough (Ok, technically they were independent with a single customer). Criterion was their brand for button rifle barrels.

Today most of their AR barrels are button rifled, made from 4150 chrome moly steel, Chrome lines, and hand lapped. To my knowledge, they are the only maker of match grade, hand lapped chrome lined AR barrels. They have expanded their product line, so they have non-chrome lined nitride barrels, and stainless barrels as well.

When comparing top quality producers the pecking orders typically looks something like this:

Accuracy:

Rifling:
Cut rifle processes, either single point or broach cut.
Button rifling
Hammered rifling

Materials
Stainless over chrome moly.

Bare steel over lined barrels, with perhaps the exception of Criterian, and FN seems to really know what they are doing as well.



Durability:

CHF over drilled barrels.

4150 chrome moly over 416r.

Cut rifling over button rifling.

Chrome lined over bare steel.



In context, this explains why the winners of benchrest matches use heavy profile, hand lapped, 416r stainless, rifle cut barrels.

And machine guns use chrome lined, CHF 4150 Chrome Moly steel barrels, typically made by FN USA.

Thanks for all the info!

If you were me, and went with a 14.5" barrel with a pinned muzzle device for a total length of 16", would you stick with the mid length gas setup?