My First AR Build

[Bruiser]

I am about to start my first build ever. All the parts have arrived.

 

From B. King Firearms ($571.57)
AP Upper, Lower and Parallax Tactical 15.5 Slim M-Lok Handguard

LR-308 Ejection Port Cover

AP Forward Assist Assy Kit

AP A2 Birdcage Flash Hider

AP .750 Low Profile Gas Block

AP Standard Charging Handle

ToolCraft .308 Bolt Assy

Magpul Moe Carb Stock

AP M5 Lower Parts Kit

 

From Armalite ($54.50)
6-Postion Carb Buffer Assy Kit

From Ballistic Advantage ($157.14) 

18" .308 Heavy Profile Rifle Length Barrel Modern Series

Rifle Length Buffer Tube

I caught some really good sales.  It only came up to a grand total of $783.21.

Hope to start the assembly tomorrow,
-Bob

Edited March 12, 2019 by Bruiser
Forgot BCG

[sketch]

welcome Bob, your well on your way! did you get the tools required.. mags and ammo ? 

[Armed Eye Doc]

Great looking kit.

[Agent Venom]

Looks great, good luck.

[Bruiser]

I have my lower built.  Had to install the mag release twice because I didn't realize the serrations go to the outside.  It wasn't pictured well on the site I found with Google.  I ended up going to you tube and that's where I saw my mistake.

 

I started on the upper.  I got the barrel dimpled and then went to install it and discovered neither of the mechanics in the garage where I work have a 1-3/8" crowfoot for the barrel nut.  I cut one out of some scrap metal we have laying around but it spread apart when I tried to torque it.  I think I got pretty close to the 35 ft lbs though and I noticed the barrel nut was not in a position where the handguard rail was close to lining up.  The handguard did come with a shim but no instructions so I if it's way off after the torqueing procedure (torque, loosen, torque, loosen, torque) then would I put the shim between the barrel and the barrel nut?  BTW, the gas tube passes over the top of the barrel nut so that's not a factor.  Oh, and what is the max torque that I want to put on the barrel nut?

Thanks,

-Bob

[mrraley]

9 minutes ago, Bruiser said:

Oh, and what is the max torque that I want to put on the barrel nut?

Thanks,

-Bob

There is a wide variation on the amount of torque on the M-15 barrel nut.

At a minimum you should have 35 ft lbs at the maximum, you could be at 65 ft lbs.

All this will vary as long as there is a notch tdc of the barrel nut for the gas tube to pass through with out touching and you have at least got your 35.

[Lane]

1 hour ago, Bruiser said:

I think I got pretty close to the 35 ft lbs though and I noticed the barrel nut was not in a position where the handguard rail was close to lining up.  The handguard did come with a shim but no instructions so I if it's way off after the torqueing procedure (torque, loosen, torque, loosen, torque) then would I put the shim between the barrel and the barrel nut?  BTW, the gas tube passes over the top of the barrel nut so that's not a factor.

I've used a Stanley adjustable wrench for this that I found at Wal-Mart. The problem here, as you may have noticed; is that the barrel nut typically has very narrow slots for the wrench, nothing I had in the house would work on it. If you're already confident making or modifying tools; you could cut a square hole in the handle for a 1/2" drive torque wrench. Just make sure you measure and calculate the torque scale correctly based on the location of said hole. I didn't bother with this because I've done so many head gaskets and valve covers that I have a reasonably intuitive feeling of what to shoot for in those torque ranges. 

Be aware; especially if your barrel nut is steel, that over-torquing could harm the upper. I've also managed to bend an aluminum barrel nut at the point where the screw holes are tapped; which meant the handguard was very crooked, and thus unusable. Had to buy a replacement nut for that build; because I was chasing that perfect alignment and didn't respect the static friction when adjusting for that final alignment. 

I would recommend tightening once, and then trying to decide how many shims are needed (did you only get one, or are there two stuck together?). Try to get it right by the third try, or else you're going to have to do it four or five times. I typically stop a bit shy of alignment and test the handguard with two or three screws, remove it; adjust again a bit at a time until it's just perfect. If you do this; try to stay a bit shy of the max torque because it's not difficult to take it too far if you're watching alignment.

I'm not sure what product everyone else recommends specifically for this; but I've always used anti-seize on barrel nuts. If you guess, and torque less than 35 ft lbs; your nut may come loose in a dangerous way after shooting a few rounds. Don't do that.

[Lane]

1 hour ago, Bruiser said:

I cut one out of some scrap metal we have laying around but it spread apart when I tried to torque it.

I'm not sure what you made this out of (or how thick it was); but have you ever tried heat treating steel? You would want to bend it back first; then heat it up beyond the curie point, and quench in cold water. I've done it with a standard propane torch more than once (might require oxy-acetelyne  if it's too thick); and it's not all that difficult. The curie point can be tested for by trying to stick a magnet to the red hot steel. If it doesn't stick at all, you're hot enough, and can quench right away. You could temper it after that by heating lightly; but it's not likely to be necessary in this case. 

[colonelrhombus]

that's gonna be a nice looking stick.  what are you using for glass?  

good call on using the AP lpk, i used a CMMG kit and the take down pins wouldnt fit.  had to spend $35 for them alone from AP.  

 

 

[Bruiser]

Here's my lower.  I haven't staked the buffer tube nut because I am planning to take it back apart to paint the upper, lower and handguard foliage green.  I just want to make sure it shoots without issue before I do that.  I wouldn't want the paint to be blamed for causing a problem...

Anyway, it could have been two shims stuck together with lube.  I didn't look at it that closely yet.

I didn't think about trying to heat treat it.  I have watched forged in fire (like the show) so I'm surprised I didn't think of that.  But, the real deal crowfoot was ordered this afternoon from Amazon.  Should be here Friday.  I hope to fab up some sort of receiver blocks out of some oak so I don't have to worry about damaging anything.

Optics...  I plan on trying out a Nikon Prostaff 3.5-14x50 SF Matte BDC scope that I bought for a Remington 700 in 308 that I never shot.  Never will either because I sold it to my gun guy when I picked up my lower ?  I had bought the 700ADL planning to trick it out with a stock and detachable magazine.  After I saw the prices of those parts I started thinking that I would be better off buying an LR308 so I have been bidding my time for the last 2 years or so.

I know this is going to sound goofy but I am so thrilled with myself for assembling the lower today.

-Bob

Edited March 13, 2019 by Bruiser

[Guest beltfed]

Looking good, have fun doing it. that's what it's all about.

[Lane]

1 minute ago, Bruiser said:

But, the real deal crowfoot was ordered this afternoon from Amazon.  Should be here Friday.

Good to hear; that will save you from any kind of estimation. As @mrraley was describing; the other type of barrel nut requires an armorers wrench (pictured), though the one I own won't tighten these types of barrel nuts (without the slots for the gas tube).

What did you do about the castle nut on the receiver extension? I see you have it fit already; did you tighten that yet? 

[Lane]

1 hour ago, Bruiser said:

I hope to fab up some sort of receiver blocks out of some oak so I don't have to worry about damaging anything.

I can give you measurements off mine; but they always needed one or two 1/8" shims to make it work right. I've made lower receiver blocks from laminated 1/8" plywood on a drill press with a compound table. Cutting wood that way with a milling bit is very easy.

Do you have plans or blueprints for upper blocks; I never found any myself?

[Bruiser]

I have only snugged up the nut on the receiver extension.  A co-worker is bringing in his armorers tool (like pictured above) for me to tighten it more for the test firing.  Once I shoot the rifle with a couple of loads to make sure it functions great I am taking it apart to Duracoat the upper, lower and handguard foliage green.  When I put it back together that nut will get tightened and staked.

Turns out there are two very thin shims in the little baggy.

I haven't found any plans on the web for a vice block.  I never even thought of looking.  I do a lot of wood working and model building so I just thought I would route out the middle of a oak block to fit snuggly over the rail so that it also touches the top of the receiver and make a second block that slides up into the bottom of the receiver and "bottoms out" on the lower edge of the receiver.  I'm gonna google it now though that you've mentioned it :)  Here we go... Should look like this:

 

Here's a pic of the barrel nut.  Plenty of room for a crowfoot on it.  You can also see that this barrel nut does not have anything to do with the gas tube.  Adjusting the nut is all about proper torque and getting the handguard rail to line up with the receiver.

 

Thanks for all the help and encouragement,

-Bob

FYI: Why foliage green?  Well I was thinking flat dark earth but then B King Firearms was having a special on the MOE stock in foliage green.  It seemed like a sign :)

 

[Lane]

Sounds like you have this pretty well worked out. I've never seen upper blocks that work that way; but that appears to be a much simpler design to fabricate.

This is what the upper blocks I have look like. They hold the upper vertically in the vise instead of horizontally. I have to shim with both AR-15 and larger .308 uppers. One shim for an AR-15, and two shims for the fatter 308 style uppers.

Since you already tried no barrel nut shim; I would recommend starting with one the next time. If it looks like you're close; don't go past alignment on your second torquing. As long as you cross the 35 ft lb mark you can back off and shoot for alignment on the third torque. If you don't think you had it, go for the second shim and see what happens. On some builds I've had to do this a lot more than three times to get it right.

[colonelrhombus]

i have several upper vise blocks, but my favorite is hands down my geisele reaction rod.  it only works on AR15s though.  

for my LR308, i use this:

https://www.guntecusa.com/dual-ar-5-56-308-cal-upper-receiver-aluminum-vise-block.html

 

got it on sale at primary arms for less than $20 if i remember right.

[98Z5V]

On 3/12/2019 at 3:40 PM, Lane said:

If you're already confident making or modifying tools; you could cut a square hole in the handle for a 1/2" drive torque wrench. Just make sure you measure and calculate the torque scale correctly based on the location of said hole.

Set the torque wrench at 90 degrees to the adapter, and no calculations need to be made.  That's the way to do it anyway, when using adapters. 

[Bruiser]

I thought about making the side clamping type of block like Lane pictured but it looked like it would be a little more in-depth than I really wanted to go and require stock larger than I have on hand.  I went ahead and made some like I pictured in my post out of pallet wood.  I think they will do the job.

Here's the blocks just sitting.  You can see the channel the rail fits into and the area that is raised to slip inside the bottom opening

 

Here they are installed.  I think that should hold it secure in the vice while I torque the barrel on.  I checked the mail at lunchtime to see if the crowfoot arrived early but it did not.

 

Side view for posterity's sake :)

 

Thanks for following,

-Bob

[Lane]

That looks great! I agree that the other style would be unnecessarily difficult to fabricate. Do you have enough clearance for the barrel nut in there; or will you need to chop off the front end of your vise blocks?

I've never crushed an upper in the vise myself; but apparently some other people have. Take your time, and don't torque the upper in the vise too hard. It needs to be secure enough to torque the nut obviously, but you don't have to go wild on it. You should actually have some advantage in that department given you are clamping the vertical instead of the horizontal. 

I had a great time with my first .308 AR build; and it looks like you are too. I got a lot of help from the great people around here along the way, and (unfortunately) got hooked on building ARs. Some say it's a sickness... But I get a lot of satisfaction out of the process, and each build becomes very personal; these are MY rifles... I loved the way you tried to make a crows foot right out of the gate.

If you get bored before the new crows foot arrives; you should try to heat treat the old one (even if you don't bend it back, and you don't need to use it). It should take you less than two minutes start to finish. Here is a look at selective heat treatment I did on some 1/8" steel. Yes; a plastic solo cup is fine for the quenching if you don't drop it in. Your tool might be large enough to require a bucket though. Have fun.

Edited March 14, 2019 by Lane
a word

[Bruiser]

Well, the crowfoot was in the mailbox at lunch time and it was a slow afternoon so I got busy.

I torque the barrel three times to 35 ft lbs per most videos and instructions I read.  I could tell that it wasn't going to line up so on the third sequence I put in one shim before I torqued it and it was very close.  I reset the torque wrench to 60 ft lbs and started to line the handguard up.  It took several tries as I would only advance it a little, then check.  Each time I had to take it out of the vice because the lower block was interfering with the handguard.  I think I did it four times and it's on the money now.

 

I think it was because I got so excited I went ahead and installed the handguard all the way and then went to put on the flash hider when I realized I did not install the gas block so the handguard had to come back off.  So then I assembled the gas block to the gas tube and what a PITA.  You need three hands but I got it done.  I finished up the install of the gas block/tube and reinstalled the handguard. 

I moved on (back) to the flash hider and installed it.  I tried to put the crush washer on backwards but soon realized my mistake because it wasn't crushing and I couldn't clock the flash hider.  Google helped me figure out it is was backwards and after I flipped it around the install went smoothly.

Next was to install the ejection port door.  Guess what?  Yep, handguard had to come back of--DUH!  For a minute, I thought I was going to have to take the barrel off and I was close to getting really upset (because of all the work indexing the barrel for the hand guard to line up) but the pin cleared the barrel nut.  This being my first time assembling an AR is quite evident by this point...  After the handguard came off installation of the door was quick.

The forward assist was very straight forward and easy to install.  I felt pretty safe in doing this again (because there was nothing left) and I installed the handguard again :)

When I get it home it'll be time to slide the BCG and charging handle in.  Then I will introduce Mr Upper to Mrs Lower and take a picture.

So close,

-Bob

[Bruiser]

Here we go...

First is the rifle sans any sighting options and something else that is very important if you want to shoot it but not entirely necessary

 

Then I went to get the optics and discovered the Nikon mount I have is not for one inch tubes so it won't work with the Nikon Prostaff

 

It looks like I will be shooting it at first with the mount and 4x scope that was on my Colt Competition 5.56 AR15.

 

I wonder if Cabela's will exchange the wrong mount for the correct one.  I bought it from them but it was a long time ago...  Still NIP though.

If they would, maybe I would buy the other thing that is missing from all these pics while I'm there.

Oh, and the weight without optics is 9.7 pounds.  My Colt Competition is 6.5 and my Sig M400 Kryptec is 7 pounds so it not only the heavy hitter of the bunch, it's also the heaviest ?

Well that about does it.  Thanks again for all the help.

-Bob

Edited March 15, 2019 by Bruiser
typo

[Lane]

Very nice looking rifle sir. Who needs a magazine? Just drop one round in at a time and get shooting! What kind of magazine are you considering? I'm not sure where you live; so you might have a lot more options that I do. 

Often I buy the magazine before any rifle parts; sort of a symbolic purchase to commit myself to the rest of the build. 

[unforgiven]

Way to go brother Bob , Cabela's is good about returns.

[Bruiser]

I think it's going to be a no-go for an exchange at Cabela's.  Apparently Nikon has re-named all their mounts and the one I have is obsolete (?) now.  They use to have the P series and the M series but now they are labeled all different.  I know they make spacers to size down from 30mm to 1 inch so maybe I'll be going that route.

 

I stopped by the base exchange at Holloman AFB and was able to pick up a 10 round Pmag for $19.99.  Not very good pricing but it was sitting there waiting for me to buy it. 

I plan on taking it out on Saturday for it's first shooting.  I have some Remington 180s and I think I might pick up a box of 150s to try both weights for function.

I'll be sure to post up the results.

-Bob

[98Z5V]

17 hours ago, Bruiser said:

I think it's going to be a no-go for an exchange at Cabela's. 

I'll buy that mount from you - I used one of them on the 12.5" Grendel, and I like it.  Just lemme know what you had to pay for it, and I'll pay for shipping from you to me, too.