Wednesday, April 29, 2015

And it's done

Here's how it went:
The last piece I needed, the crowfoot wrench, came in.  So...
It was time(cue ominous tones).

I know, lots of people have done this with no problem; after lucking out on the barrel, and getting everything else together, I really didn't want to screw something up.  So I hauled everything out to the post vise in the back yard(more space around it, better light for pictures, and this way I can pretend there's no bloody mess in the garage).

By the way, if you're thinking of building one I highly recommend the AR15 Builder site that's run by Brownell's; pictures, video, and instructions from experts on every step.

I was able to get the use of a DPMS Claw vise block for the upper;
machined nylon(it appears), you pull the pins, position the upper on it, insert the pins to lock them together, and clamp the block in the vise.  Holds everything solidly and no chance of damaging the upper.  The owner said that when it first came in an upper would not fit; it was oversize in a few places and it would've taken whacking with a mallet to get the uppper on.  Which would be Bad.  So he colored, tried, and did some scraping where needed(thus the red) and now it's a snug 'push it on' fit.

Upper installed and clamped.
That blue stuff on the receiver threads is Microlon assembly lube, I dabbed some on it and on the barrel nut threads.

Then slide the barrel into the upper, and install the barrel nut hand-tight.

The picture you can't see at this point is me with a torque wrench in hand thinking "Here goes."  The instructions said a minimum of 35 footpounds, max of I can't remember(I'll look it back up later).  I set the wrench for 35, and torqued it down.  Which didn't feel that tight.  At the Builder site they mentioned they generally got better accuracy closer to the minimum torque level, but I went ahead and reset the wrench to 40 and tightened the nut to that.  Surprisingly easy to get this done(I know, silly statement, but I'm always happy when something I've worried about goes together that easily).

Now the gas block and tube.  This is a setscrew block, when you have it in place there are two screws in the bottom you tighten against the barrel(two dimples on the barrel to match up).  First you have to put the tube in the block, which is simple: slide the proper end into the block to the proper place.  There's a hole through the block and one in the tube that align, then you drive in a roll pin to lock them together.  Getting the pin started was a bitch, otherwise they went together no problem.  Slide the block onto the barrel, guide the end of the tube into the upper, then put the block in position and tighten the screws. 

Now for the handguard.  This one comes with two curved wedges

that fit into the back end at the 5 and 7 o'clock positions,
bracing it against the barrel nut.  I found the easiest way to be slide the handguard on until a little more than the wedge length from the nut, then slide the wedges in, then slide the handguard into place.

If you look closely at the barrel nut, you'll see two grooves running around it.  When the guard is in place there are places for two bolts to slide through the guard from the right and through the grooves.  Get the bolts snugged lightly in place, make sure the rail is level with the receiver rail, then tighten them up and it locks it in place.

And that's it, the upper is done*.

The upper and lower assembled

I don't have a scale so I can't give the weight; it's heavy compared to a AR-15, but nothing horrible.  And it's nicely balanced.  I'm looking forward to trying it out.

Among the things learned in this:
It's not that hard.
It's bleeping amazing how many brands and styles and whatever of parts there are for these.
I have a set of roll pin punches, but if I were going to do this very often I'd get a roll pin starter punch of suitable size; getting the damn thing started was a pain without one.

*One thing missing: there's a place for a forward assist, which I hadn't planned on putting in, so I need to get one of the plugs made to fill the hole.


John said...

Next time file/grind/stone a slight chamfer on the roll pin. Depending on the size of the pin, spinning the pin in a drill, or a very small chuck held in the drill makes adding the chamfer easy.

Have fun shooting.

John in Philly

Firehand said...

Something I should have thought of. If there's a next time, I will

Leigh said...

An easy way to align the rail on the upper, to the rail on the hand guard, is to place the assembly upside down on a surface plate before tightening the hand guard set screws. When both rails sit flat on the surface, tighten the screws. This is especially important if you plan on installing a BUIS system on the hand guard and not the gas block. If you don't have a surface plate, a granite counter-top or good piece of steel would work. The same applies for railed gas blocks.
If you don't plan on iron sights, it doesn't matter other than aesthetically.
Nice looking rifle, Firehand. Good job. Now to build your next one. :-)

Whitehall, NY

Firehand said...

A: Good idea.
B: I haven't shot THIS one yet, dammit!

Stackz O Magz said...

Nicely done Sir. I just finished one in 7.62x39 flavor for hunting this year.

Stackz O Magz said...
This comment has been removed by the author.
Windy Wilson said...

Thanks for posting this series of assembling the AR. When I get the funds I intend to build one in 5.56 and one dedicated to .22, and you encourage me.

Firehand said...

Had I thought in time I'd have posted on putting the lower and stock parts together.

Ah well, if this helps someone it's good.