This is a copy/paste of an email I sent a friend last year on the subject:
You asked about buying an AR or getting a kit. You can come really close
to the quality of the Barrett without spending the $. The following is
cut and pasted from an email to another friend, so take it for what it's
worth. I'm not an expert, or a degreed gunsmith.
Building a nice AR:
Many folks buy a lower, a lower parts kit, and then a complete upper if
they don't have the scratch to buy an entire rifle. While this method
certainly works, it does not get you the rifle you want, only the rifle
someone else makes. Same with buying a mass-market rifle (even from a
good maker). So man the f*** up and build your own.
Parts selection:
lower receiver - milspec. There are others, like the Mega Arms billet,
but why? No one breaks a receiver without also breaking themselves.
Cheaper is better as long as they have a rep for being actually milspec.
PSA blems, other overruns usually OK. Don't get a mechanical second or
unfinished receiver as your first gun. Same with an 80% receiver - too
much work to get it right.
lower parts kit - start with a standard kit. Get a lower parts kit
without a trigger group if you can. Stay away from ambi anything except
safety selector, and that isn't necessary. Reasoning: you need to learn
the manual of arms for a standard AR if you want to be competent. Any
other rifle you pick up, regardless of additional features, will work to
that standard manual of arms. Also, once you learn the gun, you really
don't need anything extra, with a very few exceptions. The only optional
thing I would consider is one of the extended takedown pins. Leave the
pivot pin the milspec difficult to remove one - easy to pop with a
pencil, and hard to accidentally hit. Safeties - I learned to hit the
selector with my left index finger when shooting left handed, so I see
no need for an ambi selector. You might not be able to do that (issue of
dexterity and hand shape) so if that's the case the ambi's are cheap and
simple.
trigger group - if you want a standard rifle, get an ALG QMS or ACT at
45 - 75. They are worlds above the PSA or DPMS FCGs but I don't see a
whole lot of difference between the two ALG options. Next up is a $100
Rock River 2-stage match. Then the $200+ Geisselle options. Geisselle
makes the ALG stuff so it's a budget awesome trigger. But IMHO a general
purpose rifle doesn't need a $350 trigger.
Stock - I like the standard fixed A2 stock. It fits me. OTOH, it is
pretty boring and you can't collapse it. Products from Magpul seem to be
the best non-A2 option. I have an ACS on Jenn's rifle and it's pretty
nice. Their semi-fixed stock (UBR) is very nice, but an A2 is $50 and
the UBR is $250. No matter what you get, specify a milspec buffer tube.
The commercial tubes cause too many challenges in fit. Stay away from
gimmicky stocks including slidefire - fun for a range toy, not for a
defensive gun.
Upper - build your own nancy boy. The only stress is on the barrel
extension/bolt interface, which is set by the factory. There isn't much
other stress in the upper receiver if you look at it. So if you can run
a torque wrench its hard to f*** up.
I like milspec flattop uppers. Tend to run about $75, maybe $50 for a
blemish (finish blemish). Although people debate the utility of the bolt
assist, dust flap, and sometimes brass deflector, it's much cheaper to
get an upper with them and ignore them if you don't like them.
Personally I like the bolt assist and dust flap for the just-in-case
nature, and the brass deflector really should be mandatory. A DPMS
slickside receiver (none of the above) is $90 so getting rid of them not
that huge a deal if you're hung up on it. Parts kit should be milspec if
you need one. Oddly, the slickside receiver weighs almost 2x the normal
flattop.
Charging handle - here's the one place I like to go non-milspec. I like
the larger charging handles so you can use your left hand palm to charge
the gun without taking your right hand from the grip or trigger area or
dropping the butt from your pocket.
Side chargers - those are custom setups and beyond the scope of a first
AR build. But if you like them, something to work up to.
Barrel - depends on what you want to do with the gun. What caliber you
choose, and I'm not going to suggest anything, guides that and also what
bolt you use. I would tell you to do some research on your chosen
caliber to see if bolt breakage is a problem. Also, if you can buy your
barrel and bolt from the same folks so you can be 100% sure they're
headspaced correctly.
Other than caliber you have length and profile to choose. For a
multipurpose gun the 16" minimum is great. Shorter and the gun becomes
an NFA item. 14.5" with welded muzzle device is an option but adds $150
to the cost of the barrel and muzzle device, and therefore might not
really be worth it. Longer can work too if you intend to shoot longer
distances either as competition or hunting, but 16" gets you good
results to 300 meters. Most hunting in the US is at about 100-150 yards,
so make of that what you will. A longer barrel will be harder to
maneuver in a defensive situation. Barrel profile is simple - you have
lightweight, bull, and M4-ish. Main difference between M4 and
lightweight is the shape for the grenade launcher attachment, which you
can't buy anyway. If your preferred barrel/caliber comes in both
profiles, choose cheaper. If not, either is fine. For accuracy work the
bull or heavy barrel is naturally better but a lot heavier. Barrels
cheaper than $150 scare me, and more than $300 don't interest me. I like
midlength gas for everything, but better barrel makers pick the gas
system length based on measure pressure curves with the intended
cartridge. Don't buy a piston retrofit - if you want a piston gun, buy
an entire rifle set up that way from the factory. There are some solid
engineering reasons why piston retrofits aren't the bees knees in an
otherwise standard AR.
Muzzle device - get what you want. I like linear compensators but they
do add weight to the worst place possible. A2 flashhiders are fine as is
a plain barrel. You're not shooting at hajji from the dunes or in the
middle of the night so a flash hider isn't truly necessary. On the same
note, all normalish AR calibers are light rounds so a recoil brake isn't
necessary and will create more flash and noise. As I said, I like the
levang type for heavier calibers; changes muzzle jump into straight push
back which is important for back-up shots, without being a boomer. There
is also an A2 type in some calibers that has the whole bottom closed off
to get some of the same effect.
Sights - I think using a railed gas block and clamp-on sight is silly -
you're adding weight and complexity where it does no good. Either stick
with the A2 FSB, get a Yankee Hill folding, or low-profile block and
just put the sight on the foreend. For rear sights, I like the Magpul
MBUIS. Simple, light, relatively cheap, and pretty tough. Same for a
clamp-on front sight (for example, on a railed free float tube). The
Troy or Knights USMC post rear sight is pretty awesome but really
expensive for what it is.
Gas tube, barrel nut, etc should be all normal milspec unless your tube
needs a special barrel.
Fore end - how much crap do you want to hang on the rifle, and how heavy
do you want it to be? For best accuracy, any of the multitude of free
float tubes are best. You choose how much you want to pay and rails, no
rails, some rails, etc. But the M4 front furniture is perfectly OK too,
and with cheap adapters you can put a few things on them. I have carbon
free float tubes, with minimal rails, on both mine and Jenn's AR.
They're lighter than the M4 or other options, and I was trying to
lighten the rifle as much as possible. But they're not as durable as,
say, a MI FF tube with partial rails. You can spend more than the rest
of the rifle here.
IMHO a defensive rifle needs a zero-mag optic (red dot) and a flash
light of some sort. Getting those as light as possible is a good idea
for a not-going-to-afghanistan gun. The TLR1 is a good light but
expensive. Surefire P6's in a clamp work just as well. I'd skip lasers
or super-high output lights. Some folks want a foregrip, some don't. I
don't use them normally but I'm not against them - but it's another
thing to add weight.
Bolt and bolt carrier - I like M16 carriers; the added mass makes for
more reliable extraction and slows the cycle down on over-gassed guns
(think carbine length gas system). Get the bolt that matches your
barrel. 1-piece mcfarland(?) rings rather than the three milspec ones -
the 1p ring is only $3. Bolt cam pin and firing pin milspec = OK.
Retainer pin the same. I'm not sold on nickel boron coatings but it
can't hurt anything but your wallet.
Optics - get what you can afford. The Bushnell TRS25 is nice and light
and high quality - but a $1200 ACOG it isn't. IMHO it is difficult to
use a magnified optic at point blank ranges (defensive shooting
scenario). A 4x ACOG or ELCAN makes the gun much more accurate at 300
meters - but at 300 meters you're out of self-defense and well into
Murder 1. Which is OK if you're talking deer or hogs. I'd suggest, for a
multipurpose gun, a quick-detach magnified optic that you leave off
except when hunting. Red dot + magnifier is complex and heavy. There is
an Elcan 1x,4x that doesn't zoom, it just switches which sounds good on
paper but I haven't used one. Problem is too that the best reticle at
defensive ranges is a 1-2 moa dot, while at magnified distance is either
a crosshair, ring/dot, or some sort of bullet drop compensating deal
(ACOG or PSOP russian scope).
Magazines - get some. Most work. Used USGI aluminum might be beat to
hell and not work, or have brittle feed lips. Magpul G3s are awesome and
not too expensive, but only come in 5.56. I like stainless mags -
heavier, but indestructible. But if Magpul were to make a normal-AR 6.8
mag, I'd dump all 20 of my current mags to switch. Exotic caliber
choices tend to tie you into one maker's magazine, which then tend to be
expensive.
End game: if you want a defensive rifle, simplify and add lightness. If
you want an entry gun, add your laser, light, vertical fore grip, etc.
If you want a target/deer gun, longer barrel and a bit heavier
components, including a magnified scope. hog gun, MOAH POWAH (.458 SOCOM
comes to mind). Multipurpose rifle: think defensive but with better
sights. Almost all the AR calibers are light recoiling, so a lighter gun
in the long run will feel better, point better, and generally be easier
to shoot. If you intend to hunt, get a heavier caliber than 5.56, period.
To put it all together you need slip-joint pliers, a few punches, thin
knife blade for the pivot pin retaining pin, receiver block and a barrel
wrench, and a torque wrench that will do 80 ft/lbs. Maybe a (usually
3/4" open end) wrench for the muzzle device. locktite, antiseize, and
some gun oil. Can borrow receiver block and barrel wrench from me.
Building an AR is not gunsmithing, it is assembly. With everything in
milspec, even with tolerance stacking the result should run just fine.
With attention to detail for assembly, you can make a truly superior gun
with the same parts. With carefully selecting parts, you can make the
equivalent of a top-tier gun at a mid-tier price... the costs are
actually all the same, you're just supplying the labor.