I have experience with building AKs, but the AR is completely new to me and seems much different then an AK build.  Most of my questions have been solved through searching this site but I am still left with a few. Most AK barrels need to be pressed into the reciever trunion and pinned there after the correct head space is determined.  Is this the same for ARs?  Does anyone have a link to some where my question has been answered along with anything else I need to know? Any suggested reading?
- Thanks

Once you see the elegance of the AR weapon system, those AK's are going to seem like so much sheet metal junk... [;)]


Download :

TM 9-1005-319-23  Unit And Direct Support Maintenance Manual

[url]www.ar15.com/content/books/TM9-1005-319-23.pdf[/url]

No, headspace is factory set in the machining of the bolt, the chamber, and barrel extension.  You, the end user, do not "adjust the headspace".  

The "torquing the barrel nut" thing is nothing special... just that you want a minimum of 31 ft-lb, then continue tightening until the next notch lines up for gas tube clearance into the receiver.  If the notch were to line up at 31 ft-lb, you are done.

You DO need proper tools for this.  I can highly recommend you use an ACTION BLOCK and insert, not barrel vise jaws.  I know, I know, people will argue, that is not what is shown in the military manuals.  The action blocks were not made when those manuals were written.  By sheer inertia, they have not been changed.  But I can assure you the action blocks are a superior method.

You will need an M16 armorer's wrench (barrel wrench) and common automotive torque wrench with 1/2" drive.  

I don't drive roll pins with punches.  I PRESS them in with large Vise-Grip pliers, with the jaws taped with electrical tape to prevent scratching.  Grind a bevel on the ends of the pins, and put a little grease in the hole with a toothpick, and you will insert pins easily.

Nothing else requires any special tools.

The AR does not require any special amount of love to essentially 'fall' together.  An AK will not do this, sometimes even if it was once a complete rifle.  Likewise you should consider building yourself a second upper reciever and barrel assembly to take advantage of one of the AR's best features.

Cant decide if you want an A2 or A3?  Scoped or classic iron?  Have both :)

BTW, the russians built their MiG's just like the AK - hammered together sheet metal.  Amazing.  They did work, though.

Thanks for the book.  It was very informative and filled with usefull information.  I appreciate it.  After reading through, it seems like the AR, for a more advanced weapon than the AK, is easier to build.  

How much pressure does this require?  Can it be done easier with a 12ton press? As far as torquing the barrel lug, what is meant by "ft-lb"?

The 'advancement' really comes in the form of milled parts vs stamped steel.  Just like the Germans in late WWII the russians strove to make weapons with as few milling operations as possible, reducing cost and speeding production.

I don't think there's a stamped part in an AR-15, unless you count the roll pins.

....and perhaps the ejection port dustcover is stamped.

There you go.  I KNEW I was forgetting something..  Ehh... it's possible your recoil buffer tube is stamped...

But ehh, we argue whether forged vs cast is good enough to justify the price on a recvr.

Much less whether one made of stamped pot-metal will do the job :).  Can't stomp on the AK's 'bury it in mud for a dozen years, then fire it' reliability though.

Magazine load:
Dirt
Paperclip
Cartridge
Cartridge
Gas Cap
Branch
Cartridge
Leaves
Crushed coke-can
Cartridge.

Zero failure to fire / feed, etc...

Schwizzdog:  I would NOT use the 12 ton press.

With Vise Grips, pressing pins is safe and easy.

Tape the jaws with electrical tape to prevent scratching if you slip.

Bevel the end of the pins, put a little grease in the holes.

Adjust the Vise Grip so that with the pin in position (hold the pin with needle noses, if need be), with the grips squeezed closed, the jaws just touch the pin and the opposite side, whereever you are squeezing against.  No, open the pliers, and tighten the knob 1/4-1/2 turn.  Place the pin in position, and squeeze the pliers closed. Amost no pressure is required.  The pin should now be started.

Remove the pliers, and tighten the knob another 1/4-1/2 turn, and repeat.  Just a little at a time does it.

With the trigger guard, engage the front end, and swing the rear up into position.  With a nice bevel on the pin, you can easily press the pin in with the Vise Grips without breaking anything.

ft-lb is a unit of torque.  It is a force of one pound exerted at a distance of one foot.  If you look at the pointer of a beam type torque wrench, you can see a scale on there.  Go to an auto parts store, and get them to show you how to use it.  You can get a simple torque wrench for under $20.  Mine is by TRW.

The "armorer's wrench" or barrel nut wrench has a 1/2" square hole.  It is made to engage a 1/2" drive torque wrench, and be used with it.

When you plug the barrel into the upper receiver, which should be chucked up in your vise in an action block WITH the insert in place of the bolt carrier, there is a little slot at the top on the receiver.  There is an indexing pin on the upper side of the barrel that engages that slot.

Now, put some moly grease (ordinary wheel bearing grease) on the threads of the receiver and snug it up by hand.  Do this several times to spread the grease.  The purpose of the grease is to help give a true torque reading, not read the friction of the nut and receiver.

To smooth the threads, using the barrel wrench and torque wrench, tighten the barrel nut to 30 ft-lb.  This AIN'T rocket surgery, as my wife says.  Back off, and tighten to 30 a second time.

----
edited to add:

Back off again, then torque up the third and final time.

----

Before we tighten the last time, let me explain... the torque to tighten is simply an amount that will keep it from backing off by itself, and make sure everything is fully in contact, solid barrel to receiver mount.  And also that the nut is not overtorqued, stripping the thread, which happens over about 80 ft-lb.  There is no magical torque reading that will make the difference in a good running rifle and not so good.  It has NOTHING to do with headspace.

OK, now, this time tighten to 31 ft-lb.  Look at the notch nearest the hole where the gas tube enters the upper.  Will the gas tube pass through without touching the barrel nut?  You can use a drill bit shank, or the gas tube itself.  Stick it in through the notch and into the hole.  Will it swing from side to side equally?  If so, you are done.

Do not back off, you were at 31 ft-lbs, the minimum, SO, budge it a little more. Now check.  You want the gas tube to go through and not touch the nut on either side.  The gas tube needs to be able to "float" slightly, and flex, to smoothly engage the gas key when the bolt carrier moves.

Gas tube clearance should be easily obtained under the 80 ft-lb mark, and usually is done under 60.

That is it, done.

Now, if you did this with barrel vise jaws, the barrel is held stationary, and the nut is torqued against the receiver.  The receiver twists on the end of the barrel, and the hard steel indexing pin on the barrel easily dents the slot of the soft aluminum of the receiver.  You end up with the front sight canted over to one side.  Now you have to adjust the rear sight way over to one side to get it sighted in.  

Thus my advise, use an action block for barrel installation.  But use barrel vise jaws for twisting on/off muzzle brakes, comps, and flash hiders.

Feel free to email me via AR15's mail system if you run into any problems.  Hope I explained clearly enough.

A_Free_Man,
Thanks for the great explanation.  Answered alle the questions I had.  I'm planning on ordering a kit when I return home next week.  I have a lower reciever lined up for purchase, and will begin as soon as I recieve everything.  I actually belive I've used one of those torque wrenches before.  Are they the type that give way to a small click feeling when the desired ft-lb is reached?  I'm feeling very confident about puting this thing together, but for the sake of it, I've been thinking about ordering the book "Build your own AR-15" to help guide me incase I run in to something unexpected.  I also apreciate your offer to help me with any problems I run into.

No, the type I have has a beam pointer from the handle end, and a scale on the other end.  As you stress the wrench, the shaft bends slightly, and the beam points to the amount of torque.  You are really measureing flex of the shaft of the wrench.

Let me add to above.. I will edit it in, after torquing up the second time, you back off again.  THEN, run it up to 31 ft-lb minimum.