Building your first AR15 pt 2


Ammunition Office supplies Cone Bullet Musical instrument

Choosing the cartridge you want to use is also important. There are tons of different choices out there now but for the most part you will be looking at either 5.56mm or .223 Remington. 5.56mm is the NATO designation for the .223 Rem. They are virtually identical except that the 5.56 is loaded to higher pressures, therefore it is not a good idea to shoot 5.56 out of a chamber designed for .223. A 5.56mm chamber is built to looser tolerances to aid in reliability during dirty conditions. A 5.56 chamber can shoot either 5.56 or .223. .223 chambers are a little tighter and some say more accurate but you are limited to using only .223 ammo which is usually more expensive than 5.56. There is now a chamber out there called .223 Wylde which is kind of a crossover between the two. You can fire both 5.56 and .223 out of it and it is a bit more accurate than the 5.56. The chambering is decided when choosing the barrel. I personally would go with either the 5.56 or the .223 Wylde.

Most other calibers available to the AR platform will work with the standard lower including: 5.56mm, .223, 6.5 Grendel, 6.8 SPC, 7.62x39, .300 Blackout and .458 SOCOM. There are others I'm sure but these are the most common and the only ones your likely to find ammo for around here.


Here are some of the mid and high end companies out there. Too many low to even talk about

Middle: (not in any order)
Spikes Tactical
Palmetto State Armory
Rock River

High End:
Wilson Combat
Les Baer
Daniel Defense
Bravo Company
LaRue Tactical
Seekins Precision

Remember that Mil-Spec is good but not necessarily the best. Military contracts are awarded to the lowest bidder! Some things you definitely want mil-spec and others don't much matter. The biggest one is a bolt and carrier. Look for 8620 steel carrier with chrome lined carrier and gas key. The bolt should be Carpenter 158 steel and be High Pressure Tested (HPT), Magnetic Particle Inspected (MPI) and Shot Peened. The next biggest things are that the receivers are made from 7075-T6 aluminum. Forged is stronger than billet and cheaper and is the mil-spec. Billet can be compared to the bar stock in the pic below. Billet receivers are just fine. A lower is a lower is a lower. As long as it's 7075-T6 it doesn't make one difference whose name is stamped on it. Find one cheap or go for the coolest looking design.

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As I said, a receiver is a receiver is a receiver as long as it's 7075-T6 aluminum, whether it has a skull and crossbones or a prancing pony it's going to be perfectly OK. Some companies offer Billet receivers and while I don't know a whole lot about them here's what I do know. A forged receiver is cut and then "smashed" into shape while it is red hot creating the strongest material available. A billet receiver is carved from a block of material. While the billet isn't as strong as a forged receiver it's perfectly acceptable as long as it's the right material. The one benefit of a billet is that it can be found in many more exotic shapes and sizes.

Trigger Air gun Gun barrel Gun accessory Gas

Here is a list that shows who actually FORGES the receivers for different companies. Same goes for uppers, as long as it's to spec they're all the same.

Lewis Machine & Tool
DS Arms
Knights Armament

Continental Machine Tool
Rock River Arms
High Standard
Century (New)
Global Tactical
Wilson Tactical
Grenadier Precision

LAR Manufacturing
Double Star
Fulton Armory
Spike's Tactical

Double Star
Charles Daly

Mega Machine Shop
Alexander Arms

Century (Old)

Sun Devil
Sun Devil forged billet receivers

Superior Arms
Lauer (New)

Aero Precision
Aero Precision

So you have chosen your POU (philosophy of use), next is choosing the appropriate components to make it happen.

A word here, there is an AR variant called an AR-10, it uses larger parts for just about everything and is chambered in .308/7.62x51mm instead of .223/5.56mm. If you want this you MUST start off buying AR-10 parts. All the terminology and parts are the same they are just larger and beefier. For a SAPR this is a good choice but the overall cost will be approx. 50%-100% more. Ammo costs will be about double.

Another AR variant is the AR pistol. It is allowed a barrel less than 12" but MUST HAVE a pistol buffer tube which CANNOT be fitted with a stock. In legal terms once a pistol is created it can be turned into a rifle but a rifle cannot be turned into a pistol. Once a rifle is made from a pistol it must have a 16" barrel unless you have a SBR (short barreled rifle) license. You could in theory make an AR-10 pistol although I can't say it'd be practical or fun to shoot....

So here are some terms and parts you will need to know.

The LPK (lower parts kit)- is what will turn your stripped lower into a functioning gun and can typically be bought as a complete package. It will come with the trigger group, safety selector, take down pins, trigger guard, buffer, buffer tube, buffer spring, magazine catch, Bolt catch, end plate, pistol grip and several springs and detents. Some will come with a butt stock and others wont. Or each piece can be purchased individually. I got my LPK for $100 from PSA (palmetto state armory) If you think you will want any of these parts upgraded from the beginning (trigger) it might be best to buy separately although the cost might be much more than buying the kit and then swapping. Extra parts for the lower are NEVER a bad thing.

There are many parts which are being sold to replace standard parts in the LPK such as oversized mag release buttons, oversized Bolt catch buttons, enlarged trigger guards (for glove use), extended take down pins, enhanced triggers and custom engraving on everything. These I feel are just cosmetic except for the trigger and the oversized trigger guard, which has it's place though, especially around here where winter can drag on and on.... I feel that buying a standard LPK to start with is a good idea. If you feel the need to upgrade after using the basics for a while then do so. Like I said, having a few extra LPK items hanging around is never a bad thing.

Lower parts that may be upgraded or need clarification.

Butt stocks- There's a million of 'em and they all do basically the same thing. Some go for $15 and others for $150. I mean.....?

Buffer tube- The tube the butt stock fits onto and/or slides on. Two kinds, mil-spec and commercial, commercial is about .015 larger in diameter and has a 5* slant on the back end. No one can say one is better than the other just make sure your butt stock type matches your tube type. Also holds the Buffer and Buffer Spring.

Buffer- A weighted rod that the bolt recoils against during cycling. The mil-spec is 3oz. Heavier weights slow down cycling and reduce recoil while lighter ones increase cycling rate and recoil. The mil-spec is classified as a heavy but you can get heavier.

Buffer Spring- The spring behind the buffer which returns the bolt to battery after recoil. You can also change the buffer spring to slightly adjust the cycle timing although for average users this is a bit extreme. The standard buffer and spring will do just fine.

Bolt catch- The catch which holds the bolt open (back) after the last round in a magazine has been fired. Upon inserting the fresh mag the bolt catch button is pressed to release the bolt and chamber the first round in the next mag. Can also be used to lock the bolt open if you want to. Magpul sells an item called the B.A.D. (bolt assist device) lever which fits onto the existing bolt catch button to allow the trigger finger to manipulate the bolt catch. Some swear by it... I hope I never need to save that half's like $30.

Grip- What you grip duh.... like the stocks there's a million of 'em, what can I say, everyone thinks theirs is the best....If I had to upgrade mine I'd go with the Magpul MIAD. It comes with several pieces that can be configured to fit your hand.

Trigger- Very few can claim to have a mil-spec trigger because that is configured with an auto sear to allow full auto firing. What they have is the rough equivalent which is pretty basic, pretty gritty feel and has about a 6-8lb pull. The next upgrade that has any real benefits is about $90-100 while the really good ones are going for $200 or more (Timney and CMC) and are usually adjustable to less than 3lbs.

Ok, well I've rambled on here for quite a while now, hopefully this will give you some ideas of what you want to do. Good Luck!

On part 3 I will go over the Upper Receiver.

*Editors Note: After this article was written, but before its scheduled
date for being published, Olympic Arms announced that it would be
closing its doors.