I am a gunsmith and I got the bug for an AR and I'm not going to pay for something pre built. Before I get into the building of this thing I need some answers, like gas port size and how do I headspace the thing. I know there is a tennon or shank that has to be attached but is the there a certain type or cn I use a generic tpye. I am going to chamber it in 17-223 so I'll profile the barrel from a blank. Again no clue on the barrel set up. Other than that I can figure the rest. Also gas tube length? It'll have a 20" barrel. Like I said no clue.

TIA

Adam

Rifle length gas system on a 20". As for the barrel extension I imagine you can use a standard M4 extension. I would start small with the gas port hole, .060 then expand as needed until you get good results.

From my searching I gleaned a rifle length is about 12" from the reciever, correct? As for the .060" hole do I need to use chucking reamer or can I use a standard twist drill?

Adam

I would ream. Yes 12".

I would be interested in hearing who it works out for you. I have a .17 Rem and love it. I assume you will be getting like performance from the 17-223.

Most custom AR barrel makers supply their barrels headspaced with the gas port pre drilled, such as Shilen and Krieger.

Reba the OP (Ab Bentley) is making the barrel from a blank.

Yup from a blank, I am getting ready to purchase the extension and bolt so I hope to have this show underway soon. I also milled out the lower today. Some pics.







Yes it's going to be Laser Pink.

Adam

If you're gonna build it from scratch, why not build it full auto?

Pop on a regular .223 upper and rock out once in awhile.

I'm pretty sure that would get you locked up. The law is pretty clear on that one.

Yeah - not a lot of wiggle room on this one. Thanks for sharing the pictures.

Here's a link that the rest of us without a tool room have referred to, good luck with the build:

http://www.ar15barrels.com/making.shtml

No building of new full auto guns since 84 or so?? IIRC.

Can only buy whats out there for sale that had been pre registered.

Just don't want to see someone in trouble from a dumb suggestion.

I think it was 1986 that stopped all new machine gun manufacture for civilian use. There was an amendment on that bill that also would've added in supressors but it was thrown out.

The home builds only allow for semi auto and a 16" barrel, no SBR's FA or AOW's.

The gas port will depend on which buffer and spring along with the pressure your ammo is gonna run. The 17 caliber barrel will be different from a 22 bore I would imagine. Starting small and working up is a smart move.

Edit; it was the Firearms Owner Protection Act March 6th 1986, ( I had just read about the anniversary yesterday. )

Wonder what it protected us from.......

Columbine, Sandy Hook, Virginia Tech, Aurora.......oh wait, nevermind.

This is the other piece that usually gets the smooooth Operator in trouble:

http://www.quarterbore.com/nfa/dias.html

If a man can afford to feed a machine gun, he might as well do it right and buy a transferable M16 for about $15000 that way everything is legit cause unless you got a good supressor, people will take notice when you dump the first mag.

With all the bump firing does anyone bat an eye?

Well it's not full auto but it looks like it. The pictures don't even express how iridescent this bad boy is. The camera couldn't register the colors when it was wet paint.

Adam

How did you machine the square magwell corners?

Don't know anyone who bump fires but several people bat an eye and call the sheriff when you fire full auto.

Make sure you have a copy of your stamp on your person...

It was already broached. I cut the fire control pocket.

Adam

I ask this out of complete ignorance. How much do you save buying a lower you have to finish machining vs buying a fully machined lower? And why would you do it?

ab, no illegal intent suggested in any post, at all.

Bein a gunsmith, you probably have a better understanding of ATF laws, and might have a leg up anyway, on getting the proper docs to go full auto.

Little time and $, maybe some cooperation by local LEO, and you could be havin $20,000 worth of fun for $1500.

I wish it was that simple.

eh76 none to very little. But some of us like to tinker so it becomes more pride and your own workmanship.

Don't we all?

The proper FFL license is $3000, and you have to keep paying that every 3 years, or else take away your toys, er ah prototypes.

I gotta confess I only know about the FA option from a gunsmith I know that's done it himself.

He's got the rifles, and ain't wearin orange (yet).

So, as I understand it, a shiznitload a $ turns a bad guy into a good guy.

There's no way I could argue with that logic.

Sorry for the hijack, ab, wishing you no runout.

Unless he's got the proper manufacturers license, he's just been lucky but of course now they're loading up the black helicopters to pay you a visit for a little info. Maybe water boarding?

Sorry just playin. I don't know all the ins and out of the law but dealer samples come with lots of strings.

I'm betting it's more about not having a serial #, there called 80% lowers!

No real savings over a serialized lower, if you buy a "lable" lower. I bought this one for $25, but the mill I used cost $975. The simple fact I made it work and I don't have to mess with paperwork also makes it an easy decision for me.

Adam

*BTW I never had any plans on making this into a SMG. That was a suggestion from one of the replies on the thread.

If they are still calling, you aren't shooting enough!

LOL, not me, I'm a poor boy but I have a friend who's neighbor called on him after 4 or 5 years. I've got another friend who faced the SWAT team at his door, he told em it wasn't him but they didn't believe him till the guilty party started blasting again down the road.

Aside from the FFL, ITAR is around $3000 per year too.

It's a pretty expensive proposition to start putting ARs together.

So here is "Franenstein in Pink". I needed a barrel, well i didn't want to pay for one. I looked thorugh the barrel bucket and low and behold I had nearly new 223 Remington sporter barrel. **back story: I was going to use a 17 caliber barrel but I decided to test it out on a standard caliber first, also I didn't have a 17-223 reamer and wasn't going to wait** So I found out some measurements (.8125 OD, 16tpi, and about .620" long) and started cutting. So now I have a Remington Sporter barreled AR. The best part about it is the chamber is already there and all I have to do is touch it up once I am done. I also am thinking of tapering the ID of the gas block instead of cutting a flat for the gas block seat. All in all this has been a great project and the satisfaction of knowing how to build these rifles and barrels is truely great.















Adam

Cool picks

It's been 27 years since I've seen a high speed tool post

I would rechamber with a good reamer. Remington has some of the worst chambers ever cut in factory rifles.

This barrel cuts pretty well for a Remington. I have a new 223 reamer waiting for the cut. I think it'll shoot well.

As to the HSS tool post, yeah, low tech = cheap.

Adam

Great thread! Inspiring if I might say so.

Can you show/explain how you got or get the barrell extension on the barrel and how you got the head-space to be just so? I have always been confused about that process.

Great pictures!

Mr. White,

It's all about math. You measure the extension depth minus the lug thickness from the back of the extension. I'll write a better explanation here in a few.

Adam

http://firearmsdesigner.com/?p=153

Mr. White this is where I found most of my info.

Adam

Ok, I have a question for you AR gurus. Are MilSpec bolts all similar? I mean to say this: could I use a seperate bolt to headspace and chamber? I know that people slap on uppers and bolts eveyday with no issues.

Adam

Thanks for that link! I always wondered how that was done. Great read.

I hope an expert will give you an authoritative answer on this one. The only way to adjust head space is to remove the extension and adjust the cut on the shoulder where the barrel extension hits... correct? Or is there something that can be done to the bolt? I have always wondered. With all the barrels being sold for do it yourself assembly I had always assumed that the bolts were all made to tight consistent tolerances as well as the barrel extension installations at the barrel manufacturers. From what little I have read here and there folks can double check head space with go and no go but I never read anyone say how they corrected it.

99% of us can't correct the headspace if it fails the gauges. It's time for a new barrel or bolt, or both.

Correct. Insert the bolt into the extension and measure. This gives you your actual depth. I add .005" to that to compensate for crush when torquing the extension on.



I would say factory tolerances are loose enough to work withing the specs of military tolerances. Much like SAMMI specs.

Adam

Once headspace is set, barrel extension pinned, the gas port is drilled TDC and you better hope your bolt matches the one it was set to. The only way to change it is to remove the barrel extension, cut off the exact amount of barrel so the gas port lines up with the pin at TDC and rechamber.

I've never seen a new bolt not pass the field gauge but I still check when buying a new barrel.

If your headspace comes up too short, run a reamer in and turn it by hand. That will give you the few extra thou you need, because you ain't going to get anything swapping bolts.

You can grab random bolts from 5 different vendors an not find a thou and a half difference between them. From the same maker? Chances are they will all be within a half thou. Most places chamber close enough that they grab bolts out of a bin and don't even bother with a gauge.

If you come up too long, well, that's a problem as others have pointed out.

Got a little more done today.



Adjusting the shank length



Shank adjusted and headspaced



Final shank length, time to check chamber depth and ream accordingly.



Go gauge to check headspace.



The nice thing, when I face off the barrel it almost was perfect protrusion. In this case .131" with the Go gauge.



Once the chamber was cut to proper depth, I put a 29* cone @ .570" wide for proper feeding.


Tomorrow I'll torque the extension and drill the gas port. I may or may not put a compensator on it.

Adam

I also have to turn down the shank to 1". Adam

I set of the muzzle and indicated it in. from there I did a small floorboard crown and polished to mirror to ensure no burrs or scracthes.







Next I set the barrel between centers and prep'd for cutting the shank to 1".







Good results.



Tomorrow I have to turn the barrel down as the gas block will not hold steady enough to taper the hole, win some lose some.



Adam

Well today was a slow day, I got to work on the gas block. I reamed it from .625" to .675" this way I don't have to contour the whole barrel just a seat at the gas port.



Adam

Well finished it up today, well as much as machining goes. I had to turn the gas seat (PITA) and then I torqued the extension on. I set it up in V Blocks and leveled it, used a pin to find top dead center and then moved down until I hit the mark I transfered to drill the port. I used a center drill to peck the starting hole. Then I started with the .060" drill bit and moved up to .073", bur free and right centered on the land and groove. After that I used the barrel spinner and cleaned up the barrel.

Now I just have to paint and test fire.

Adam

Adam looking good! Thanks for the pictorial.

Really enjoyed this thread.

Looks like an extremely short gas system for that barrel length. Any reason you chose that length?

It's not too bad on length, but it's shorter than I expected. I ordered a rifle length gas system and when I received it the tube measured out to 12". It's was the correct length but shorter than I anticipated. I really needed the 14" tube, so I compensated with a smaller port hole. All of my research yielded no informant on barrels over 20". Since this is a learning experience and not a production rifle I figure of it gives me fits I'll chop a few inches off the barrel. On that same note I couldn't find any contradicting information that said I couldn't go with mid length tube and a 23" barrel. I found information on AR15 barrels dealing with pressures in the 223/5.56 and with this system I figured I'll be running about 20k psi at the port since I used a port .010" smaller than recommended. Again if my dwell time is too long I'll chop and re-crown.

Adam

20k? A rifle gas on a 20" barrel is smooth because it runs at 13.5k.

Interesting.

I may be wrong. I'm just using the math provided by the chart. It may be lower, but again it's a work in progress.

Adam

Well I shot the upper today. I was pleasantly surprised, it cycled soft and smooth with no hiccups. The brass ejected fine and didn't hit the deflector. This was with a CAR buffer, tube, and spring. I didn't have optics on it so I don't know the accuracy of the barrel.

Adam

Wow--quite the thread. Congrats on building it.

pic of the finished gun?

Please!

Well about that. I used a lower from an MP to test the upper. I am still waiting for my parts to come in from Palmetto Armory. In the interm I think I'll build a space stock as I just have a buffer tube and can't find any YHM lightweight thingys laying around.

I'll post pics as I progress and next week I'll have a scope on it to test accuracy.

Adam

I believe I'll wittle out a 80% in the next couple weeks or so

I have an upper with no stampings........it would make a nice pairing

I had to abandon the pink one for now, put too much paint on it on critical areas. But I present the Franken-Stoner.

Adam

Well I should have known that my SwarTasco scope was too good to be true, shot the AR today and the 4th shot the scope took a crap. It went from groups to patterns. I put my Leupold EFR AO scope on and a good cleaning so tomorrow I'll give her another go.

Adam

I would have bet it was too low myself

Ted,

It wasn't that it was too low, it was the fact the windage turret took a crap. It couldn't handle the 120MOA I needed to put on it to get to 100yds.

Adam

Well maybe it wasn't the SwarTasco. I went and shot it with the Leupold on it and it shot the same. I checked the crown out and sure enough one the legs on the carbon star isn't like the others. Telling me I dinged the crown at some point. So back on the lathe it goes. All well, it happens.

Adam

A poor crown will open up groups but something else seems out of square

I pulled the barrel tonight and nothing else is out of square. The gas tube isn't contacting the key, the rings are tight, the barrel torq'd properly. I mean it is a factory barrel and could be [bleep] to begin with, but I doubt it. I am banking on the crown and that little nick I see on the land.

Adam

Some goods reloads and presto.

Adam

Congrats! It was fun watching this one go together.

Yes as TC1 said it has been fun watching the progress.

Thanks again for the compliments. It was a fun project. I think I might have to make a few more of these things.

Adam

Finally got it out to 200yds.



22gr H4198
40gr Nosler Varmagedon
Fed GMM Primer
OAL fit to magazine
Leupold VX2 3-9x33 AO

Adam

ME TOO!

What happened to the neon color scheme??????

For those that haven't messed with Duracoat, it goes on thick and doesn't come off. I got the paint too thick in critical areas so I had to make up another. I spent 45 mins blasting that receiver and still couldn't get all of the pink off.


Adam