AR-15 uppers & lowers?

[A.Rex]

Reading through Shotgun news I keep seeing uppers and lower or upper reciever and lower reciever, etc. I thought the reciever was ONE unit. Enlighten me.

Plus, what is all this other gear? It looks like you could practically assemble what you want in whatever configuration. Kinda swell.

 

[hk_cqb]

Really green, huh?

The lower receiver holds the trigger group, recoil assembly, buttstock and most important, the magwell. Since the lower is where the magazine attaches, this part is regulated by Federal and State law. Purchases of lower receivers must go through an FFL.

The Upper receiver holds the barrel assembly, bolt carrier group, charging handle, sight assemblies, gas system. The upper is NOT regulated yet (see S.609) and can be purchased by a non-FFL holder.

It just adds versatility to the AR15. With one lower reciever assembly, you can have multiple upper receivers for different purposes.

M4- upper for CQB and ranges up to 150 yards.
Heavy Barreled Varmint Upper for 'yote hunting out to 500 yards.
DCM upper for Service Rifle competitions.

Go post your questions over on AR15.com and you'll get much more info there.

 

[Navy joe]

Not w/ the AR family. The lower houses the trigger group,magwell, mag release and mounts the stock. The upper is connected to the lower by 2 pushpins and houses the bolt carrier group. Attached to it is the barrel. The lower is the only controlled part in a semi AR, all other parts can be purchased w/ no background checks.

As for all the other parts, yes you can assemble most anything you want, BUT it might not be legal. Unless you are building on a lower reciever that was pre '94 "assault weapons" ban assembled there are restrictions on what parts you can use such as bayonet lugs, threaded on "flash hiders", collapsible stocks and so on. Even on my pre-ban there are restrictions, for instance I can call Bushmaster and order an 11.5" machine gun barrel and slap it on. Don't mean its legal. Same goes for any M-16 fire control parts in the lower, etc. Not a lawyer, educate yourself a lot more before you build or buy any Frankenmousinguns.

 

[dZ]

the Lower receiver is the registered firearm that requires an FFL and a 4473 form

even if it is stripped (sans all internal parts)

the upper reciever is not a gun
it is just a gun part and requires no paper work to purchase

of course the upper has a barrel and a chamber and a bolt and a firing pin...

the modularity of the AR system is one of its coolest features

 

[Karsten]

A.Rex
That little AR Critter is a marvel. If you think a Cadillac or Lincoln has options, look at the AR's.
First you need to find the company and deside say BM, DPMS and a few others (that was a hint
Lowers are just that lowers, Upppers are the tough part. Barrel lenth, sights, flat top, bull barrel, M4, M3, M2 and hell who knows.
Check out http://www.youngsguns.com or http://www.gunsonsale.com and study what is available. After picking the AR configration you need, go buy it locally if possible. but the first time out, buy a complete gun. Get good, start putting them together from parts.
Myself, I bought a BM VMatch with a 16 inch barrel and I know what my next one will be also.
Check the boards also for stuff also, mags, ammo and other things.

 

[Q-Man]

A.Rex,

You bought an M1A and now your interested in AR15s? Are you sure you aren't my long lost twin brother?

Here are some pictures of upper receivers:

Post-Ban 20" H-BAR (Heavy Barrel, no bayonet lug, no flash suppressor):

M4 14.5" (Standard barrel profile, with bayonet lug and flash suppressor. The barrel is below the 16” legal minimum and the rifle this upper receiver is installed on must be registered as either a machinegun or a pistol with the BATF.):

20" V match (floated barrel and "flat-top" for mounting a scope)

Lower receivers aren't quite as customizable. It’s mostly just the stock that people customize. There are basically two different options for stocks: Standard A2 (as in M16A2) and collapsible (such as the stock on the M4 carbine).

Lower receiver without a stock:

Lower reciever with a standard stock:

Collapsible stock for the lower receiver:

 

[Paochow]

I recently bought a Pre ban Colt R6601 AR-15 and I'm planning to buy an M-4 style upper (16.1" barrel) in the next few weeks, but was wondering if I should buy an extra bolt, so I am not swapping them between the two uppers. The uppers I have been looking at are sans bolt.


Also I have been told that I will need to check headspace on the new upper before firing. I understand that Go-No go gauges are available, but could use a little advise in finding reference materials on how to adjust headspace.

Thanks.

 

[radom]

The newer made lowers do not fit on the new uppers unless you do a git of fitting. I tryed to put my old milspec M-16 upper on a new bush and the upper would have needed the back of the receiver filed down about 1/64th to fit. They do not want any new stuff to fit right on old preban stuff I think.

 

[Q-Man]

You mean you put your old permanently disabled almost mil-spec M-16 upper on a new (post-ban) lower, because otherwise you might have committed a felony by violating the '94 crime bill.

 

[uglygun]

Bushmaster hasn't gone and done anything to try to keep a person from mounting an M16 upper on their postban lower. The uppers are virtually all identical to one another. The problem you ran into was very likely just a lucky instance of having to parts that were slightly out of spec and not within a tolerance level that allowed them to be mated to one another. Something was out of spec but I highly doubt it was intentionally done by any of the manufacturers. Colt is notorious for putting things into their guns like a sear block that won't allow you to close the upper if you've got an M16 bolt or non milled AR15 bolt carrier in it, the Colt bolt carriers also have been milled out at the back so that they can't be used with a "lightning link." Bushmaster on the other hand hasn't taken these steps towards political correctness.


Bushmaster preban and postban upper assmeblies are both made using the exact same stripped upper receiver forgings and are finished to the same specs, there is no preban or postban specific upper receiver or lower receiver forging.


Modularity is the goal and every once in a while an upper and lower might need a little fitting but on a whole they don't need it.

As for putting an M16 upper assembly on a postban lower, DUMB! First, the M16 upper if it had an M16 bolt carrier in it could be considered an illegal machine gun by the BATF since it has in it one of the parts needed for a full auto M16. The other thing that would be a "no no" would be having an M16 upper with it's "evil" features like the bayonet lug or the flash suppressor on it, putting an upper with preban features on a postban lower would be considered manufacturing an illegal assault weapon.