AR build and beating the odds.

[arthurcw]

What does one do to improve ones chances of making a reliable AR?

This question is based on a comment by the venerable Zak Smith for another thread:

The chances that a "home built" AR-15 will have reliability problems is a lot higher than a factory-built or high-end "custom" rifle. It is certainly possible to build one (ultimately it is a person putting a rifle together) but the odds are not in one's favor.

So what does a person do to increase his/her chances of making a reliable rifle?

I’m sure the list starts with using quality parts and limiting the amount of WECSOG by using proper tools, but what else can you do?

There doesn’t seem to be a lot of wiggle room in an AR build beyond that.

Please let it be known I’m not disagreeing Zak at all. I just want to know what a person can do to even the odds. The fact I don't know means I'm probably on wrong side of the math on this one.

 

[Coronach]

My guess (and that's all it is, a guess) is that the reason for this comment is that most home builds are done in order to save some money. This means the builder probably buys what is cheapest (within reason), as opposed to what is best. Add in the fact that most builders are first- or second- time builders, sometimes without proper tools, and you end up with assembly errors on top of questionable parts. Not a really great way to go for an AR.

My guesses as to how you can improve your chances are:

1. Know what you're doing. At the very least have a good book (IIRC Scott Duff has a good assembly book, but I'm too lazy to go to my book case to see if he is the author), but preferably have a good book and a friend who knows what he is doing, especially when you are installing the barrel.

2. Buy the right tools.

3. Use top-of-the-line parts.

Mike

 

[vzenmn]

Buying quality parts and getting a chrome lined barrel would be my first bet. And don't forget feeding it good quality ammo.

 

[strat81]

Mags, followers, feed ramps, buffer springs, buffers, bolts, carriers, barrel extensions, carrier keys, gas tubes, gas ports, ammo, lube... all of those can contribute or detract from reliability.

Also, how reliable to you need it to be? Is it a SHTF gun, a duty gun, or a bench rifle? If the rifle pukes at the range, you'll be okay. But if you're LE and your rifle goes down, you might be dead.

 

[Soybomb]

I agree with coronach, I think alot of people are trying to save money and buying junk. If you don't know the differences in the parts available, perhaps you shouldn't be deciding that the cheap one will work just as well. I also am not convinced that most people have much ability to read and follow simple assembly directions.

I also think strat has a good reminder. Colt might be one of the gold standards, but is it a big deal if your weekend plinker has a failure now and then? Nothing wrong with saving a few bucks here and there sometimes.

 

[Tarvis]

I'm getting pretty sick of hearing "use quality parts, not the cheap stuff" in reference to building an AR. WHOSE PARTS? WHAT BRAND? All I ever hear is "spend more money" and never who to spend it on. Are we talking about lower parts kits? Are we talking about an expensive BCG? More expensive barrel? No one has mentioned a SINGLE manufacturer that has the best lower parts kit. No one has mentioned a SINGLE TRAIT a good barrel has other than it is expensive. Price is a function of And then there are little gems like these:

Mags, followers, feed ramps, buffer springs, buffers, bolts, carriers, barrel extensions, carrier keys, gas tubes, gas ports, ammo, lube...

Great. Fantastic. I now have a list of parts I should look at. What will I find when I look at them? Not a frickin clue. Need good buffer springs and a good buffer? As far as I know, mine is milspec. Need a good BCG? AFAIK mine is milspec with a properly staked gas key. What were you trying to tell me, that these parts will affect reliability? HOW? WHAT DO I BUY TO KEEP THEM FROM BREAKING??

Still haven't learned anything, only that I should go broke.




As you can tell I am very frustrated. AR conversations drive me up the frickin wall some times.

 

[Coronach]

The real problem is that fanboyism and armchair commandos tend to drown out real, experienced voices in this conversation. The other problem is that there are no real easy answers for a lot of the questions.

My opinions?

LRPK: CMMG has a very decent, fairly priced LRPK. The trigger is nothing to get excited about, but all of the rest of the parts are pretty run of the mill and OK. Most people want to fiddle with the triggers anyway, so buy the kit, and it you want to upgrade the trigger later, have at it. Most of the stuff (FCG excluded) on the lower is stuff that is hard to get wrong, or stuff that can be observed as wrong through visual inspection.

Triggers: I have a RRA NM trigger in one of mine, and it works fine. Others have had problems with them. However, for inexpensive upgraded triggers, the RRA-NM is about as good as it gets. You can also pay more and get a Giselle (match style trigger), or pay more and get a JP (combat style trigger). I've only played around with them and can only say this: they're really good triggers by feel, have really good reps for working right, and cost a lot more than my RRA.

Receiver extensions: Get a milspec tube, not a commercial tube.

Stock: these are pretty hard to screw up. Magul, Vltor, other gucci-gear stocks all work well and have advantages over the standard m4 stock, but you know what? the standard m4 stock works.

Uppers: Any of the milspec uppers will be about as good or bad as any other one, as long as we're talking stripped uppers. If you want to pay a little more, Mega makes a good upper that is, supposedly, more dimensionally correct than the run of the .mil stuff, and that's probably good. They're still reasonably priced. If you really want to make sure you have something dimensionally correct and well made, go with Larue Stealth or Vltor's MUR. Be aware that they're significantly more expensive, and you're into the realm of paying 50% more to get .5% more performance. Only you can decide if it is worth it.

BCGs: Here is where the experts will say to pour some money. Get a shot peened and MPI'ed bolt, and get a well made (Bravo Comapny, Colt, LMT) BCG with properly staked carrier key. Yes, this stuff will cost more, but these are the parts that break. if that doesn't matter (range gun, plinker), just get whatever cheapest. It will probably work fine anyway. if this is a "serious" gun, don't screw around with it- get something top of the line.

Charging handle assembly: Word is that some CHs are really really chintzy. I dunno who makes bad ones versus good ones, but mine appear identical to every other AR out there, and mine came from RRA and CMMG. They seem to work fine.

Barrels: CMMG makes good ones for fair prices. If you're looking for match grade, try White Oak Precision.

That help?

Mike

 

[Coronach]

Also, M4 feed ramps vs regular ramps is another question, along with chrome vs non chrome barrel.

In truth, I don't think it matters too much either way*, but if I was going through the hassle of ordering parts and building my own, I would go chromed barrel for a "combat" gun and match barrel for a precision gun (few (no?) match barrels will give you the option of chrome), and M4 ramps on both.

Mike

* one area where you can screw this up is this: do NOT get an upper receiver with M4 feedramp cuts and a barrel extension that doesnt have them. Much unhappiness results.

 

[For Freedom]

If this worries you, consider G3, FAL, M14, and AK-type weapons.

 

[Zak Smith]

What does one do to improve ones chances of making a reliable AR?

Parts are just one aspect of it. A "quality part" may be a liability if it is the wrong part for the application. A part marketed as or assumed by "internet warriors" to be some type of enhancement may not be - and in many cases is not - an improvement.

The AR-15 is a machine. It is a machine with moving parts. Some of those parts must fit together with critical alignment, engagement, or clearance. It is a dynamic system in which extreme pressure is vented from the barrel to put the action into motion. The action's cycle time and speed is affected by a host of parameters and environmental/input factors. Each aspect of the dynamic system interacts with other aspects with reliability implications. Once past reliability, many of the same factors come into play with regard to accuracy (and consistent accuracy).

Still haven't learned anything, only that I should go broke.

Let's say you want to build a car engine. But you have no experience as an auto or engine mechanic. Do you think the most important question of success is that you buy expensive and quality components-- or that you have proper training and experience actually building engines.

That's how you beat the odds.

-z

 

[Zak Smith]

If this worries you, consider G3, FAL, M14, and AK-type weapons.

I've seen people attempt to use the majority of those in training classes or 3-Gun matches. All can be screwed up by putting them together wrong or adding parts that harm reliability.


"woops"

............... Larger version of above photo.

-z

 

[Bartholomew Roberts]

Buffers: Your buffer should be a solid, mostly metallic unit. It should not be plastic. It should not be filled with shot. Buffer weights are as follows (should be within 0.05oz of the listed weight):

Rifle: 5.2oz
Standard Carbine: 2.96oz
"H" (Heavy) Carbine Buffer: 3.77oz
H2 Carbine Buffer: 4.55oz
H3 Carbine Buffer: 5.43oz
9mm Buffer: 5.60oz


Buffer Spring: Should be free of kinks or obvious weak spots. The military maintenance manuals call for the following lengths:

CARBINE: 10 1/16 inches (25.56 cm)
minimum to 11 1/4 inches (28.58 cm)
maximum.

RIFLE: 11 3/4 Inches (29 85 cm)
minimum to 13 1./2 inches (34 29 cm)
maximum.

As far as whose parts/what brand, I think that is difficult to say. Even on manufacturers with good reputations, you get variances from lot to lot or they start cutting corners once their product gets successful. I tend to agree with Coronach's opinions, only I would add Young Manufacturing to the list of BCGs that I would consider.

There are also some newer BCGs on the market with all kinds of proprietary, no-lube necessary, harder than diamonds type coatings. I haven't tried those yet, so I can't comment much but sometimes too much efficiency (in the form of reduced friction, increased hardness) can be as hard on a firearm as not enough. If the designers expected to overcome X amount of force and you have now reduced it to M amount of force with your space age aftermarket reliability enhancer, what happens when your same weight, harder than diamonds space age part impacts with the regular old GI parts at the higher velocity imparted by the regular old GI parts (which were designed to overcome the higher friction of the GI part you replaced)?

If I were building myself, I would stick very closely to the types of parts used in military firearms because they have been extensively tested and there is a wide body of knowledge about them. When you start throwing in custom parts (like say an MSTN lightweight bolt carrier), you also need a custom builder (like MSTN) who knows how that parts change affects the overall system and what else needs to change.

One of the greatest strengths of the AR (mods o' plenty) is also one of its greatest weaknesses - because it allows guys who have no clue to add aftermarket parts that "enhance reliability" but were really designed to "enhance reliability" for a very specific and narrow area.

One good example: the LMT Enhanced Bolt Carrier. This is a quality product from a well-respected manufacturer. This bolt carrier featured a third hole in the BCG to bleed off more gas. It was designed to help enhance function for a very specific problem - the longer dwell time caused by a 16" barrel with a carbine gas system. In that system, the third hole helped vent the extra gas pressure. However, put the same BCG in a 20" rifle and you are now venting the gas you need to make the rifle run. It has gone from a reliability enhancer to a reliability problem.

So the AR's modularity means any monkey can play "monkey-see, monkey-do" and take parts meant to address specific issues (full-auto suppressed use) and then add them to their regular 16" carbine where they cause malfunctions and consternation ("I just spent $1000 on this rifle and bought a shiny new $100 reliability enhancing buffer and it still chokes on every round!")

 

[ceetee]

You can also have the best of both worlds by buying a complete upper receiver, and separate complete lower receiver.

You can pretty much configure an upper receiver from any of the major vendors (Del-Ton, Rock River, etc) however you want it. Barrel lengths, rates of twist, sighting options - all choices can be pre-ordered, and factory-assembled. Likewise, you can order a complete lower receiver with your choice of furniture and trigger. Doing it this way will still save you the 11% excise tax, but you won't be able to spread the cost out over time as much.

 

[taliv]

tarvis, for quality, cost-effective pieces parts, go to Bravocompany. buy their BCG.

for lower parts, you can buy colt parts from brownells.

for barrels, the most important thing is what chamber you get. if you think all 5.56 or 223 are the same, you're not paying attention. many companies (e.g. LWRC) don't advertise that they have 'improved' the chamber similar to the wylde. others (e.g. Noveske) advertise their improvements.

If I were buying a hard-use barrel, I wouldn't go to some place like White Oak. i'd go to larue or noveske or dennysguns. however, all my competition barrels are done by white oak. it's a right-tool-for-the-right-job kind of thing.

i have an adjustable gas block on my carbine class gun, but i built it before i knew better. i've been lucky and it hasn't caused a problem yet, but I sure wouldn't repeat that. however, I did get another adjustable block on a competition gun. square pegs, square holes.

more later,

 

[Tarvis]

Parts are just one aspect of it. A "quality part" may be a liability if it is the wrong part for the application. A part marketed as or assumed by "internet warriors" to be some type of enhancement may not be - and in many cases is not - an improvement.

That is exactly what I'm talking about. First it was "buy expensive and quality parts," now I need to watch out for "upgrade" parts because they won't work? How about an example, eh?

So, as far as the LPK goes, the only difference is on the FCG (which I have a good understanding of); Good. Now: the BCG, which has a huge part in the function of the rifle, upgraded BCG's are bad?? LMT's upgraded BCG will not work for 20" rifles? I think Zak had it right when he said:

Do you think the most important question of success is that you buy expensive and quality components-- or that you have proper training and experience actually building engines.

The only thing to do now is figure out which parts are upgrades for a certain setup and down grades for others, namely which parts are down grades for which rifles. Like the "super duper upgrade light weight hydraulic" buffer that is supposed to reduce felt recoil. Will this not work in certain rifles or have an increased chance to fail?

I think I need a book, am apprenticeship under a gunsmith, and a few pills.

 

[Zak Smith]

How about an example, eh?

The Accu-Wedge is a classic example of a part that solves a "non-problem" but has demonstrated that it can cause reliability problems. You can put recoil buffers in the same category. I would also add some aftermarket gas blocks (those that do not employ a physical block to movement such as a barrel divot or pin) and adjustable gas blocks in some circumstances and/or those that are not "fixed" properly. Heavy buffers in semi-auto AR-15's are a band-aid which can mask other problems with the gun or magazines.

-z

 

[Tarvis]

I understand 5.56 vs .223 and what chrome lining does. I sit here all day and read. I've been reading pert' near every AR thread that has been on the first page for 2 months. The stuff I need to know is which BCG, barrel and possibly buffer type stuff, but all the more important is why. My brain will not understand an answer unless it understands why that is the answer. For example, why no adjustable gas block on a carbine? No need, or because it will fail? I can see why there would be no need, as all the thing has to do is cycle, whereas a bench/comp gun would benefit from having just enough gas to get the empty case ejected and feed reliably, but that doesn't make it a component likely to fail, right?

Also, what does Bravocompany do that makes their BCG's better than a "standard USGI" BCG I'll get with a kit from m-aparts.com?

I must be typing slow because my answers are getting posted before I can get the question out. Thanks guys, I'm getting smarter.


Edit: Also, a gunsmith buddy of mine asked if I was timing the disconnecter, which can apparently cause the rifle to fire before the bolt is closed. He then showed me a destroyed BCG and receiver which caused me to wonder. Is this an issue with LPK's or no? I didn't put many rounds through my first build before I sold it and I haven't shot my second build yet so my experience is very limited, in either case I haven't seen a problem thus far and neither have my buddies that bought kits from the same place.

 

[Coronach]

Tarvis, it depends on the "upgrade". Some improvements aren't. Basically, most of the things the experts recommend doing are not examples of using something New! Improved!, but using something that is actually milspec as opposed to a cheaper, nonspec part. A prime example of this is the bolt and BCG. Some makers cut corners and save money by using nonMPIed bolts and doing substandard assembly. The good makers don't.

Mike

 

[Jeff White]

Tarvis said;

The stuff I need to know is which BCG, barrel and possibly buffer type stuff, but all the more important is why.

Buy a bolt carrier group from Colt (SAW LE Sales sells genuine Colt parts), Bravo Company USA or LMT. Why? These products have been proven to actually meet the design specification. They are properly heat treated, shot peened and magnetic particle inspected. The carriers are chrome lined on the inside.

Other manufacturers do not build their parts to spec because of the cost. Quite simply they wouldn't be able to offer their ARs and parts at the price point they hit if they did.

Also, what does Bravocompany do that makes their BCG's better than a "standard USGI" BCG I'll get with a kit from m-aparts.com?

See above. The Bravocompany parts do meet the specification. Who knows what standard USGI really means? Anyone can say standard USGI because it means whatever they want it to mean.

Jeff

 

[Zak Smith]

For example, why no adjustable gas block on a carbine?

What happens when the adjustment screw falls out?

What happens when an aluminum gas block expands at a faster rate than the barrel it's clamped on?

Etc....

 

[Tarvis]

EXCELLENT! More and more knowledge. So would you say that LMT, Bravo Co and Colt are all equal in quality to the extent that I won't notice a difference? I am a bargain shopper (like many) but at the same time, but I pick out what I want then try and find the best price, as opposed to choosing solely on price.

Can anyone describe the shot peen, MPI and heat treating process, including it's affects (why it's done), how it's done and what will happen if it's not done? I know, I'm knowledge greedy .

 

[arthurcw]

Glad I started this thread. good stuff. thanks.

 

[Gary G23]

My experience has been just the opposite. I have owned 20 AR's over the past 20 years. My last four frankenguns that I still own have been a LOT more reliable than the first 16 factory guns.

The reason is quality parts. I have seen so much go wrong over the years I am convinced that parts make a big difference.

All of my builds have the following features:
4150 barrel steel Nato chamber chrome lined (my barrels are Sabre, LMT, and CMMG)
M4 feed ramps
Stag or RRA lower parts kits
mil-spec receiver extension (Vltor or Stag)
M16 bolt carrier group with MP tested bolt and properly staked gas key (I use Bravo Company or Denny's Super Duty)
CMT/Stag charging handle

Three out of four of my current rifles have a midlength gas system.

The only variable in my builds is extractor tension and buffer weight. IMO the correct way of determining this is to take the gun to the range after you put it together and try it out. Use the heaviest buffer that your gun will cycle reliably with. In a carbine using M193 ammo that may be a H, or H2, or whatever. Two of my midlengths have H buffers and one has a carbine buffer. It's easy to tell at the range. Swap them out and see what works best. I do a quick triple tap to test if I have slowed down the action too much.

Carbines require more extractor tension than midlengths do. A carbine may work fine with a 5 coil extractor spring, black insert, and crane O-ring but that will probably be too much for a midlength. I never put the O-ring in a midlength build. Also a Wolff spring may work better than a BCM 5 coil spring in the longer gas system. If your empty cases barely clear the ejection port you may have too much extractor tension.

It's like tuning a car. You can tell right away what works best.

Also use good ammo. I primarily use some sort of M193. Either Winchester Q3131A, or Q3131, or Federal XM193, or Prvi M193.

And don't forget good magazines. I've probably bought 200 -300 mags to end up with 100 good ones. My first choice is Magpul PMAGs. My second choice is Okay/NHMTG aluminum mags with Magpul followers. I haven't been able to get consistent reliability out of any other brands.

 

[strat81]

Great. Fantastic. I now have a list of parts I should look at. What will I find when I look at them? Not a frickin clue. Need good buffer springs and a good buffer? As far as I know, mine is milspec. Need a good BCG? AFAIK mine is milspec with a properly staked gas key. What were you trying to tell me, that these parts will affect reliability? HOW? WHAT DO I BUY TO KEEP THEM FROM BREAKING??

Still haven't learned anything, only that I should go broke.

If you quoted the rest of my list, you'll see that I specifically said all of those can affect reliability.

I never said you had to go broke, either. There's plenty of gear you can buy for an AR-15 that'll cost you a fortune and not affect your reliability at all. Usability, maybe, but not reliability.

Consider handguards and rail systems. Plain, M4 handguards should not affect reliability in anyway. Neither should 2-pc, non-floating rails that use the existing hardware. And technically, even free floating handguards themselves should not affect reliability. However, if the personal installing said FF handguards messes with the gas block and installs it wrong when he removes the stock FSB, yeah, you'll get problems. That's an assembly issue, not a part issue.

Same goes for carrier keys. They best carrier in the world isn't worth squat if the keys aren't staked properly and they end up backing out.

Crappy factory ammo or crappy reloads can wreak havoc on even the best guns. They'll short stroke, misfeed, fail to go into battery, blow primers, blow cases...

As for what's what, DO SOME RESEARCH. Stop being lazy. Do you think you're the first guy to ever build an AR-15? I'd bet that almost every question you might have has been answered. Use Google and search THR and Arfcom. The Arfcom tech forums are a wealth of info.

 

[benEzra]

You can also have the best of both worlds by buying a complete upper receiver, and separate complete lower receiver.

I was going to suggest that, but you beat me to it!

I think a big part of the problem is that a lot of people come on here and say, "What's a good first AR?" and there are about 50 replies saying "Don't waste your money on a factory assembled gun, build your own." When, in fact, a newbie who has never even field stripped an AR, and doesn't even know what all the parts do, is vulnerable to a lot of pitfalls.

I am pretty competent mechanically (I fix my own cars, repair electronic equipment, build stuff), and I would not, at this point, consider myself competent to build an AR as reliable as a factory gun from loose parts. Give me six months or a year shooting and field-stripping the platform, to really grok how it all works, and then maybe I'd attempt a kit build. But I think that urging people to build their own as a first AR is not necessarily the wisest counsel.

I think purchasing an assembled upper and lower from a reputable manufacturer, or even buying a complete rifle, are probably a better approach for a first AR. At least that way you know more what you're getting, and if there's a problem a good manufacturer will resolve it.