View Full Version : assmebling an ar 15 upper?

01-28-2010, 2:13 PM
I haven't really found the upper I wanted at the price i wanted so i'm looking at just buying the upper receiver getting the barrel i want and the front hand guard i want and all that.
but my question is how hard is it to assemble them all together? and what all parts are needed?
It's my first ar15 build, and i've built the entire lower from a parts kit and stuff. But like when i went to install the buffer for the stock, i realized i had only got the buffer tube and was missing the spring and buffer and locking plate and locking nut.
Anyways, if it's a big hassle i'm just gonna buy a complete upper and learn to work on it, and build an upper for my next ar. but like i said, how hard is it and what parts are need to assemble a whole upper?


01-28-2010, 2:18 PM
Torque wrench, barrel nut wrench, vise, and upper fixture holder should be good enough for a basic build. If you're messing with the FSB, muzzle devices, and special handguards you'd need more stuff.
Follow the torque values and verify headspace.

01-28-2010, 2:58 PM
If you don't have the tools, it's a LOT cheaper to come over and have me do it for you.
I charge $25 to assemble an upper from a box of parts.

01-28-2010, 2:59 PM
In a nutshell, connecting the barrel to the upper is simple.

If you plan on buying a bare barrel and installing a FSB or pinned gas block, it'll get a bit trickier as you will have to drill holes in the barrel for the pins.


01-28-2010, 3:06 PM
Also, I'm not sure what you're looking at in an upper, but if price is a concern, you may want to re-consider buying an off the shelf upper. They'll often times be cheaper than building your own.

If you do decide to build your own, also factor in the cost of the tools you'll need to buy. Like Randall said above, it'll be cheaper to just go to him. $25 is a great price, you can't even buy a barrel nut wrench for $25.

01-28-2010, 3:15 PM
I re-barreled an upper in the desert with only a barrel wrench, a Leatherman Wave and my knee....that being said, I would take Mr. Rausch up on his offer.

bare minimum tools
1) barrel wrench / muzzle device wrench.
2) Wall nail to drive pins using the flat end against the pin so you dont deform the pin.
3) A secondary tool for hammering and griping the Gas tube without crushing it and to manipulate the barrel slip ring.

Its not hard as long as you understand what is going on and where things need to go to line up.

01-28-2010, 6:50 PM
Ok since we are on the subject is everything in the uppers pretty much uniform or are there some things to really look out for.

Let me see if I an clarify. I have heard that the barrel lugs an the bolt mating is really crucial an it isn't just drop in. That the bolts will not turn an engage the lugs an there is gun smithing that needs to be done to make them fit. Other people say that is total horse c$$p an putting a BCM bolt assembly in a Armalite carrier to a bushmaster barrel will fit every time.

I have only looked at complete uppers because I just don't know enough about this particular area to trust what anyone says..present company excluded.

I have 2 KD lowers just sitting here all built an ready for uppers but I can't find what I want for the price I could build one for. I would just hate to put the money an time in, an have the damn upper grenade on my the first time out. Not to mention the yelling an screaming involved too.

01-28-2010, 6:57 PM

There's a slot in the receiver and a pin on the barrel.
Most of the time, the barrel just slips into the receiver and it all works.
Occaisionally, there's a problem, but it's usually bad parts.
There is usually some slop between receiver and barrel and that's where exxperience helps you to know how to deal with it.
Occaisionally, a bolt will have problems aligning to the lugs, but again, it's bad parts or excessive slop.

01-28-2010, 6:59 PM
I have built several uppers and have swapped bcgs before. I have never experiences the lugs not locking. Something would have to be seriously out of spec. Headspace is another issue, just try to atleast use high quality parts. Try to stick with new parts but little use is alright.

Building an upper is really easy. IMO it is easier than the lower. Do it, it's lots of fun, you learn more about the rifle and you can build it exactly how you like.

01-29-2010, 2:20 AM
I just did it for the first time. It's easy. However, you should purchase the right tools for the job. If you plan on building more uppers or you just like to put things together yourself, it's worth it.

If you like things to "just work" then have Randall do it. He comes well recommended on here. And, yes, $25 is a great deal for what he's doing.

Action block- ~$40
Armorer's wrench ~$25

This is assuming you have a proper vise, torque wrench, and correct grease.

Of course, if you have to drill for the taper pins, it gets more complicated. Just get a clamp on block or drill and tap the FSB for set screws.

If you're buying quality new parts that conform to milspec, you should have no headspace problems. If you're mixing/matching new/old bits and stuff with questionable tolerances, you should most definitely check headspace.

01-29-2010, 6:06 AM
If you don't have the tools, it's a LOT cheaper to come over and have me do it for you.
I charge $25 to assemble an upper from a box of parts.

+100%. If you lived in my neck of the woods, I'd tell you pretty much the same thing (depending on certain variations of f/r sight types, etc.).

01-29-2010, 1:28 PM
interesting stuff guys!
any place to find instructions for doing all this? maybe a picture guide, cause i get what you guys are saying for the most part but without seeing it i'm drawing a blank on it.

01-29-2010, 1:37 PM
Read through this thread, it has lots of pics and good info on assembly:

What are the specs for the upper you want? If you cannot find one with the specs and price you want it's probably because what you are looking for is unreasonable. There are SO many to choose from you should be able to find what you want at the right price.

01-29-2010, 1:41 PM
The issue with asking for instructions is that it is completely dependent on the type of handguards. Since most handguards attach in different ways, there are many different proprietary barrel nuts for each handguard such as the DD Lite, LaRue, YHM, etc.

ARF has a decent guide for different handguards, starts abot 1/3 of the way down: http://www.ar15.com/forums/topic.html?b=3&f=4&t=226782

Midway guide on building a 204 varminter: http://www.midwayusa.com/midwayusa/StaticPages/pdf/Instructions/AR-15%20Varmint%20Rifle%20Instructions.pdf

01-29-2010, 2:11 PM
Its cake to build an upper. If you want custom, doing it yourself it cheaper. If you want basically a factory upper, the factory one will be cheaper and come with a warranty.

01-30-2010, 2:18 AM
Thanks all for the info. I have completely dismantled my other AR's with no problem when cleaning etc. I have the knowledge of how the rifle goes together just wasn't sure about the lugs. I never changed out BCG just because of what I had been told. Just didn't want to damage my babies.

I am being unrealistic in price I know. The upper build I would like is a rail hand guard, middi or carbine not a biggie to me. 16" with flip ups for around 700. I know even with the cheaper extra components it just isn't going to work. I don't want to go with stag that would keep the price down but used stuff so far has all been with A2 front block an I want Lo-pro for a rail an will eventually drop on a clone o tech for optic. Just wanted to build a rife for less then I could buy a completed. Oh well, again thanks for the advice an info it is greatly appreciated.