AR build advice appreciated

[cmdc]

I just ordered a BCM Enhanced Lightweight 16" stripped barrel and want to build an upper around it. Unfortunately for me, even though I have quite a few ARs, I know next to nothing about building one. In keeping with the lightweight barrel, I want everything to be light and minimalist, and compact, so I need some input about things like the gas block, BCG, muzzle brake/flash hider, handguard, etc.

Any help would be appreciated. Intended use will be HD and general shooting.

[rickyrick]

Hand guard is the big decision and can be the most expensive part of the gun.

Get a reputable BCG.

Probably want a lo-pro gas block.

Gas tubes abound.

You'll need to decide whether or not you want FA and dust cover. It's easier to go with FA (foward assist) but a little weight can be trimmed.

My advice is to get on the hand guard first, as lightweight is costly at times.

[HughScot]

As far as how to build one the following video is very good. Then you can get specific as to brands, etc.

https://www.youtube.com/watch?v=p8sY5CQmlHI

[Aquajunky02]

As far as building one goes they aren't very hard. I just finished building my first one a couple months ago. My advice is do lots of research and watch lots of YouTube videos. Decide exactly what your looking for your gun to do and have a plan before you start getting to much stuff. I kept mine fairly simple. The most expensive part of mine was the Daniel defense chrome BCG. IMO it was worth the extra money. It's a breeze to clean. I've put about 500 rounds through mine so far without any failures. They are fun to shoot, but even more when you built it. Good luck on your build and keep us posted.


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[Ibmikey]

For receivers get Aero Precision..great quality and added nylon tipped screw to take up space ( if any) between upper and lower, and threaded hole for take down spring plug.

[Old Bill Dibble]

If you are building your own go ahead and get a Nickle Boron BCG. It is only a few dollars more and well well worth it.

[bedlamite]

I'd keep a FA BCG for reliability, but the Handguard can save weight:

https://www.midwestindustriesinc.com...tegory_id=2471

[stagpanther]

You probably don't want to hear this--but I personally don't see a whole lot of value in pencil barrels--I think you're going to be throwing a ton of money at a mirage.

[marine6680]

Depends on how much you want to stick to the lightweight theme.

If you are willing to part with the cash, you can get titanium parts for some of the things you need.

The KMR rail from BCM is o e of the lightest around. The KMR-A isn't too bad on weight either. And a careful search can net you a decent lightweight rail for not too much money, but it will not be as light as the specialty ones.

That will be your biggest weight savings is the barrel and rail. Followed by a titanium gas block and flash hider.

That will eliminate as much weight as possible from the front end.


Beyond that, lighting the parts in the receiver is next, but that weight won't really do much for the balance and handling as the weight on the front will.

[cmdc]

Thanks for the input so far. I ordered a NiBo BCG, a 10" keymod handguard, VG6 muzzle brake, and a mispec receiver.

The lower I'm going to use has a carbine buffer, but the upper is midlength. I'm thinking I should get an H buffer for it. Do I need to get a stronger spring, too? Like I said, I'm new to this build business.

[Aquajunky02]

Originally Posted by cmdc

Thanks for the input so far. I ordered a NiBo BCG, a 10" keymod handguard, VG6 muzzle brake, and a mispec receiver.



The lower I'm going to use has a carbine buffer, but the upper is midlength. I'm thinking I should get an H buffer for it. Do I need to get a stronger spring, too? Like I said, I'm new to this build business.

I'm no expert by any means, but I would try it out before I changed anything. Why fix something if it's not broken? If you try it out and it doesn't perform as you expected then look into changing things.


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[Aquajunky02]

Since most problems that require heavier buffers seem to stem from overgasing I would think a better solution would be a quality adjustable gas block?


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[bfoosh006]

I agree with Aquajunky02...

don't jump the gun, on a different buffer yet.

My 14.5 BCM enhanced fluted ( I love ) is one of the softest shooting middies I have.

You can always get a heavier buffer later.... ( rather then having a unused collection of buffers at home , Lol )

And no offense Stagpanther, ( and I respect your opinion on pencil profile barrels )...but the profile on a BCM Enhanced LtWt. is much better then a pencil profile to me.

Its tapered barrel is stiff where needed with as little weight out toward the muzzle as needed... it is not designed to be a match barrel. IMHO... just a better balanced and designed lighter barrel.

It is so much better balanced, that I can "feel" the difference between the 14.5" and the 16" ELW barrels on identically set up rifles.

[Dirty_Harry]

I disagree. I don't think enough people use lightweight barrels enough. Sure longevity and accuracy (with prolonged fire) is better with a normal barrel, but average joe won't tell the difference. I have 2 BCM lightweight builds that are quickly becoming my go to guns.

[Independent George]

Originally Posted by stagpanther

You probably don't want to hear this--but I personally don't see a whole lot of value in pencil barrels--I think you're going to be throwing a ton of money at a mirage.

I tend to believe the opposite; I think pencil barrels make a lot of sense for the average shooter who can't shoot 1 MOA even from a bench, and likely wouldn't wear out the barrel in a lifetime. They don't cost much, and weight savings makes a big difference in handling and ergonomics.

I think it's the match barrels are a waste for all but the most dedicated shooters; they're just too big, heavy, and expensive. People buy them thinking they'll be shooting at 500 yards every weekend, then spend 90% of the time inside of 100 yards, and the other 10% inside of 200.

[stagpanther]

I disagree. I don't think enough people use lightweight barrels enough. Sure longevity and accuracy (with prolonged fire) is better with a normal barrel, but average joe won't tell the difference. I have 2 BCM lightweight builds that are quickly becoming my go to guns.
__________________
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I'm sure they are fun and handy--I just think that they are money pits to get meaningfully lighter than a "regular" AR--but what the hey--have at it. : )

[rickyrick]

My experience, rifles with heavy barrels are more stable than light rifles. The same mass that causes you to maneuver slowly also dampens operator input such as, heartbeats, breathing and twitches. Lightweight setups lend to quick maneuvering and bringing on target quickly.

So I would choose a light gun for action activities and hunting at short ranges, in brush and stalking and the like. I would choose heavy for supported shooting, medium range hunting and so on.

[Independent George]

Originally Posted by stagpanther

I'm sure they are fun and handy--I just think that they are money pits to get meaningfully lighter than a "regular" AR--but what the hey--have at it. : )

If you're talking about things like titanium gas blocks and magnesium alloy receivers, I agree completely; you end up paying something like an extra $100 for each ounce saved.

With barrels, though, I think it's money well spent if reducing weight is the objective. To go back to the OP's barrel, BCM's enhanced lightweight barrel is 22 ounces, compared to 28 ounces for the standard barrel, for just $30 more. That seems very reasonable for a 20% weight reduction. I just don't see $30 as a 'money pit'.

To use another popular manufacturer as an example, Faxon's 16" government profile barrel is 26.4 ounces and $169. For a whopping extra $6, you could get the Gunner profile (21.9 ounces) or the pencil profile (19.04 ounces).

I understand all the tradeoffs in weight vs performance (and, honestly, I do think the pencil profile goes a little too far), but if low weight is the objective, the barrel is probably the most efficient place to spend your money.

[marine6680]

CMDC

An H buffer seems to be the standard used now by most quality manufacturers. (non-budget models)

BCM uses H buffers in their midlength rifles.

I run an H2 in a couple of my midlength rifles with no issues even with cheap/weaker ammo. I have an H2 in a BCM build... it works great.

BCM Does their homework and picks a good gas port size, so you shouldn't have any problems with over gassing the rifle... So don't worry about an adjustable gas block.

[cmdc]

As to buffers, what are the criteria for determining which weight? I'm assuming it has to do, in part, with ammo weight.

I'm going to get an H buffer for the build because that's what BCM uses in their rifles. Do I need just the buffer or do I need a different spring as well?

I will be shooting up to 77gr wt ammo.

[g.willikers]

One approach is check to see what the manufacturers are using for their offerings.
Quite a few are now building and selling light weight models in an effort to return to basics.
Just a thought.

[bedlamite]

cmdc, it's not really about the bullet weight, it's the amount of gas the system gets. More gas requires a heavier BCG and buffer, a lightweight buffer and BCG may require an adjustable gas block to cut back the amount of gas. You really won't know for sure until it's assembled.

[10thMountain]

First, I think you need to decide on Billet vs Forged receivers:
Billet - fancy, "different," more expensive (possibly stronger)
Forged - cheaper, cookie-cutter (but possibly lighter)

[rpseraph]

As far as how to build one the following video is very good. Then you can get specific as to brands, etc.

https://www.youtube.com/watch?v=p8sY5CQmlHI

Along with Sootch00's video: https://www.youtube.com/watch?v=V1RdhoW8_fY

Sounds like you have all of the parts... what you'll also need is the tools. If you buy yourself an upper receiver block, armorer's wrench, and torque wrench you'll be out over $100 bucks. Ideally you have a buddy that has some of those things! It will make your build a lot easier and prevent screw ups.

Worst case, swallow your pride, bring your parts of a local gun shop and ask them to help you put it together, a good armorer will maybe even just let you use the tools and teach you.

[WhyteP38]

As far as barrels go, I've built several 16" M4 configurations and several 16" pencil configurations. Each has its pros and cons. Overall, I much prefer pencil barrels and have never found them to be "money pits."

As for buffers, in very general terms, you want the heaviest you can get that still reliably cycles based on the ammo you'll use. Note that a change in ammo may change reliability (frankly, I think the wrong buffer weight is the culprit for guns that can't shoot weak Wolf polymer or Tulammo). Here's the Cliff's Notes version of why the buffer is so important.

When a round goes off, the case stretches to the dimensions of the chamber. At that point, there's tension between the chamber and the case. The weight of the buffer, along with the power of the recoil spring (and the weight of the BCG to a lesser degree), provide resistance to the force of the gas used to cycle the bolt.

If extraction happens too early (too light buffer), the rearward pull of the extractor claw on the case rim can rip off the rim due to that tension. Or, a weak extractor claw will slip over the rim and leave the case in the chamber. Even if none of those things happen, the BCG and buffer's rearward travel can be harsh.

If extraction happens too late (too heavy buffer), there might not be enough power to fully cycle the bolt, leading to short stroking.

For those reasons, I suggest getting a carbine buffer and an H3 buffer. They're relatively simple to take apart, and you can create an H or H2 buffer by swapping the internal weights. Thus, buy 2 types, have options for 4 types.

For me, the mounting of the barrel to the upper is where I pay special attention. My understanding is that a high torque value (60-80+ foot pounds) will degrade accuracy, so I have barrel shims on hand in case I need them. After reaching minimum torque and aligning the barrel nut teeth to allow for gas tube insertion, I then remove the mounting block, insert my BCG (without the bolt), and put the barreled upper back in the mounting block to fine tune my alignment by making sure I have equal clearance on both sides of the gas tube where it enters the upper. I use a piece of old gas tube for this step (you can also use punch or section of wire of the right diameter). Next, I remove the barreled upper from the block, attach my gas tube, and check for binding by turning the upper upside down (to simulate the upward pressure of rounds from a mag), and then sliding the BCG in and out. I'm looking for no (ideal) or minimal drag. If I have any doubts, I'll use a magic marker to blacken the inside bevel of the gas key, run my test again, and check to see where I'm getting wear.

If it's either right or left sided, I make adjustments to the barrel nut until I have no drag. Usually, it's minimal and either at the top or bottom of the bevel. I leave that alone. I've read that you can tweak the gas tube up with a thin block of wood or down by pulling on it with a cord, but I've also read where such tweaks don't work when the gas tube gets hot because it reforms to its original shape.