Advice on my first AR build

[bfro5482]

So I’m planning out my first build and have done a ton of research on setups and components. From a high-level, I’m considering ....

- 16” 556 mid length barrel (probably Aero Precision complete upper)

- Carbine stock

- Two stage trigger (LaRue)

Any big picture thoughts ...

1. 16” Carbine versus mid length?

2. Two stage trigger on a 16” barrel?

I’m still learning here so any thoughts or advice would be appreciated.

 

[12Bravo20]

The Larue two stage will be fine. I use them in a 308 build, several 5.56 builds and 22lr builds. My 308 is a 20" barrel, My 5.56 build are either 16" or 18" and the 22lr builds are 16".

With the 16" barrel, the mid length will be a bit smoother than a carbine length. Either will work fine with a carbine stock setup or rifle length stock setup.

 

[IdaD]

I really like a mid-length gas system on a 16" barrel, just my personal preference.

 

[Tirod]

Midlength is the proprietary length preferred by makers for 16. Carbine is for 14.5, Rifle is for 20. The gas port goes about 5" behind the muzzle to get the correct TIMING and keep pressures reasonable.

By timing it's the dwell - the delay where the bullet passes the gas port and then travels to the muzzle. That allows gas to travel to the bolt just right for the barrel length, with the appropriate port size.

When you use carbine gas the port is even closer to the chamber, pressures are sharply higher, and when it was introduced in the salad days of M4geries, it caused high pressures in the bolt carrier, unlocked the bolt sooner than needed, maintained high pressure in the case requiring the extractor to literally pull against the rim and it often ripped out. It didn't give the case time to contract and be released from the chamber wall.

After all that you get high bolt carrier speeds which causes the bolt to often override the cartridge rising up in the magazine, and the bolt also smacks the barrel extension so hard it bounces off unlocking. If you hit the trigger at the 'wrong' time then the primer activates just as the bolt unlocks and starts extracting a round, which then blows out the case and the volume and pressure of the gas at a 55,000 peak then damages the gun. And the shooter.

Carbine gas on 16" were then found to cause a lot of Customer Service issues so the makers pulled away from it. It was never milspec, midlength actually follows the correct interpretation for how it should work - if the military had ever issued a 16", which it did not.

Carbine for 14.5, midlength for 16, there is a longer version for 18, and rifle for 20. Don't measure from the chamber, measure from the muzzle and don't mix and match.

 

[bfro5482]

The Larue two stage will be fine. I use them in a 308 build, several 5.56 builds and 22lr builds. My 308 is a 20" barrel, My 5.56 build are either 16" or 18" and the 22lr builds are 16".

With the 16" barrel, the mid length will be a bit smoother than a carbine length. Either will work fine with a carbine stock setup or rifle length stock setup.

Thanks for confirming this setup will be smoother than the carbine. That’s also why I’m using the two stage trigger, for improved accuracy.

With a 16” mid length barrel, can I run a standard carbine setup with a regular buffer (3oz)? I think the answer is yes .... I don’t think I need a heavier weight.

 

[12Bravo20]

Thanks for confirming this setup will be smoother than the carbine. That’s also why I’m using the two stage trigger, for improved accuracy.

With a 16” mid length barrel, can I run a standard carbine setup with a regular buffer (3oz)? I think the answer is yes .... I don’t think I need a heavier weight.

Yes you should be fine with a standard carbine buffer.

 

[MistWolf]

...can I run a standard carbine setup with a regular buffer (3oz)?

Carbine buffers (3 oz) are too light, even when an AR is properly gassed. It allows the reciprocating mass hit the back of the receiver extension harder than it needs to resulting in sharper recoil. H buffers are good, H2 buffers are better.

Spring quality in a firearm is very important. One problem is the quality of the extractor spring. Most companies use the wrong spring which usually fail between 750 to 1500 rounds or so, especially with a heavy firing schedule. (Such as shooting a couple hundred or more rounds in an afternoon.) Be prepared to replace the extractor spring with a Colt or Sprinco M4 spring.

After the extractor spring, the springs I've seen give trouble most often are the hammer spring and action spring. However, most companies get those right.

Another important detail is gas port diameter and system integrity. Which gas port is correct depends on the combination of barrel length and port location. (Also, whether or not you plan to shoot suppressed, but that's another level of education in itself. Let's learn the basics before going down that rabbit hole!) Gas integrity isn't hard to achieve. It's easy to make sure everything lines up and doesn't leak.

Next, just make sure the feed ramps of the barrel match. These days, almost all flat top uppers and barrels have M4 cuts. Just to be on the safe side, double check.

The rest- lower parts kits, trigger groups, furniture and sights is relatively straight forward and usually dictated by personal preference.

PS- You can save money by getting a set of drop-in handguards from Magpul other than going for the free float tube right away. That will get you shooting right away while agonizing over which free float tube is best for you- or even if you need a FF tube. Again, this is personal preference.

 

[Varminterror]

What are you wanting to do with the rifle?

Generally, I recommend folks skip a 16” AR as their first. Most civilians just don’t have enough use for a fighting carbine, beyond making noise, and most don’t spend that much time making noise.

Most folks also want greater consistency from their AR’s than typically delivered by clamshell assemblies.

I generally recommend an 18-20” barrel, free float, H2 buffer in a carbine stock, and a mid weight barrel with a .750” gas block journal for a beginner’s first AR. It’ll shoot small, it’ll shoot far, it’ll shoot fast... won’t do any optimally, but will do all of them sufficiently well.

 

[sarduy]

So I’m planning out my first build and have done a ton of research on setups and components. From a high-level, I’m considering ....

- 16” 556 mid length barrel (probably Aero Precision complete upper)

- Carbine stock

- Two stage trigger (LaRue)

Any big picture thoughts ...

1. 16” Carbine versus mid length?

2. Two stage trigger on a 16” barrel?

I’m still learning here so any thoughts or advice would be appreciated.

- 16” 556 mid length barrel (probably Aero Precision complete upper)
This is a very good choice, i have a 14.5 and a 16” uppers from them and i can tell you, they are nice.

- Carbine stock
Yes, adjustability is king.

- Two stage trigger (LaRue)
No need unless you want a precision rifle. A light single stage is very fast and crisp.

Any big picture thoughts ...

1. 16” Carbine versus mid length?
Both are great for an all around 16” AR. I own both, love both. Go with the one your heart desires the most, it will make you happier.

2. Two stage trigger on a 16” barrel?
Again, not really needed as a first rifle, maybe as a 2nd or 3rd build yes.

 

[MistWolf]

Why do people assume a two stage trigger is only needed for precision shooting? Is the two stage trigger in the 03-A3 or Garand a precision trigger? There are some single stage AR triggers that are better suited to precision match shooting than duty or defense use.

Back in the day, shooters chose to replace two stage triggers with single stage triggers for shooting matches for better trigger control. They were tuned for a light pull, as little creep as possible and minimal over travel.

For speed shooting, the two stage G trigger isn't really any faster than the standard AR single stage. Travel till break and reset are about the same distance for both triggers. The only real difference is the G trigger reduces pull of the initial take up (creating a first stage) and adds weight to the pull right at the breaking point (creating a second stage).

 

[Boomholzer]

I think most people assume the opposite in a fully supported AR platform for a trigger. Mixing platforms. Work from the muzzle back to the chamber.
16" for 556 or 223 loads, maybe target loads? Intent?
I don't have input on AP barreled uppers. The rest is a AR-15 and furniture, including the trigger.

 

[Dibbs]

Find the barrel you really like, before you begin. Most of the other parts are much easier to come by.
If you are waiting on a barrel, it can hold up the build, for weeks.

 

[twarr1]

+1 Mid-length gas system. You’ll do good getting a complete Aero upper. It’ll have the correct port diameter. Carbine length gas systems and adjustable gas blocks will probably just frustrate you on a 1st build.

 

[MistWolf]

Carbine length gas systems and adjustable gas blocks will probably just frustrate you on a 1st build.

A carbine length gas system with the right diameter gas port on a 10.5 to 16 inch barrel won't be frustrating at all.

An adjustable gas block does require a little bit deeper knowledge.

 

[twarr1]

I should’ve been more clear, I’m not trying to discourage anyone. I meant buying a complete Aero upper vs building one from components. (Barrel, extension, nut, port, etc.) I agree there’s nothing inherently difficult with carbine gas systems.

 

[H&R Glock]

Don't forget the tools you will need to build it. Watch a few You Tube videos and make a list of the tools that you think you will need and/or try to borrow them from a buddy. Driving and starting some pins without the proper tools can be a frustration. Some tools you can get along without, but I don't recommend it.