# Not an engine, but a project I expect some will appreciate



## Sixtysixdeuce (Oct 24, 2014)

It is dubbed AR-7.5,  a 50% scale AR-15.  I give you my partial build as it sits now, nearing the close of week 3 and after about 75-80 hours of machine and finishing work:












  That is a normal 5.56 size AR receiver on top.  Don't know how many we have here who are familiar with the AR-15, but for those who are, the scale should be rather striking.

Now, before anyone asks, yes, it is 100% legal in the USA to build your own title I firearm for personal use.  They needn't be serialized, and they can even be legally sold at a later time, so long as they weren't build with the intent to sell.

  Anyway, I still have a long, loooong way to go.  Chambering is going to be .17 Mach 2, which is a .22 long rifle necked down to .17 caliber.  I still need to procure a barrel to modify, as rifling barrels is one thing I'm not yet equipped to handle.  I have not yet made: Barrel nut/Delta ring ( will be one piece), front sight, flash hider, forward HG retainer, hand guards, charging handle, stock, faux gas key, buffer, bolt catch, magazine catch, extractor, ejector and firing pin.

  This is where it all started with a piece of .860" 7075-T6 on Sunday, October 5th:
















  Carving trigger, hammer, disconnector out of D2 tool steel:
















  Installed, and receiver extension housing threaded (5/8-24):






  Unfortunately, I totally forgot any pics while I was carving out the selector.  Oh well.

  Moving on, now time to get after the 6061-T651 upper half:






  Threading the barrel housing in 3/4-28 before cutting away too much material, which would risk tweaking the piece:






  Starting to show signs of life:






  In the rough:






  The pint sized homogenous bolt/carrier I cut from an air hammer chisel.  Should last forever, but it was slow going.  This super tough, super hard alloy destroyed a half dozen carbide end mills and over 20 HSS, TiAlN and cobalt drill bits
















  In the upper, as I try to gauge depth for the modified Savage Mk II mag that will be used until I get around to making a forming die to do scale magazines:






  Today was receiver extension ("buffer tube") day.  Also cut from 7075-T6, this is how the bulk of it was formed:






  Using a 7" long 3/8" carbide end mill and trying to keep the piece rigid enough to avoid chatter proved futile.  I just resigned myself to the fact that there would be a couple blemishes that even 2+ hours of hand finishing wouldn't remove.  Next time I'll use a 7/16" 4 flute for this process.


  It will be a fully functional 6 position carbine stock, which I will be carving out of ABS as I did the grip.

Remember, I have no CNC capability.  This is all done on these 3 machines:
















And with a lot of elbow grease using die grinders, dremels and assorted hand tools.

  So that's about it for now.  When completed, it will be a 50% scale blow-back operated pistol.  I say pistol, because the stock will obvisouly be useless at only 5.2" fully extended.  Hopefully ATF will agree with me and allow this to be a title I handgun rather than forcing me to register another title II short barreled rifle.  We shall see!


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## Swifty (Oct 24, 2014)

Although I'm not a gun fanatic, I do own a couple of rifles for target and hunting, although I haven't fired then for at least 2 years. I can still appreciate the machining work going into your project. Here in Australia we have very strict rules when it comes to owning guns of any sort, no auto or semi auto rifles anymore, handguns are only to be used at a pistol club (I'm talking about the general population now, not security or police). There is still a big, but very misguided push by certain elements to have all firearms banned, but we do have good representation by the Sporting Shooters Association of Australia.

Whenever I go into a gun shop, I almost feel guilty because of all the bad publicity we have here whenever a gun is involved in a crime.

But, as I said at the start of this post, I can still appreciate the work that goes into machining anything, whether it is guns, engines, static items that have been machined for the pleasure etc. Please keep us informed as to the progress of your project, I for one would like to see how it turns out. 

Paul.


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## Omnimill (Oct 24, 2014)

Fantastic project and I'm very envious that you're able to do this. Will be watching your progress.


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## gbritnell (Oct 24, 2014)

Leaving all the politics aside you are doing some outstanding work on this piece. I see in the one picture you have a threading die on a boss with an end mill in the center of it. What exactly was your machining step here?
And as far as manual machines go, almost everything can be done on them given the time and ingenuity. 
gbritnell


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## gus (Oct 24, 2014)

Here in Singapore,it is almost impossible to buy and own a gun. Had to go for interview to get Spear Gun License.  Armed robbery is death sentence.  If Gus is caught making his own gun,it will be a tough 5---10 years in the slammer. A BB gun will get me into deep trouble.

You made DIY Gun making so easy. th_wav


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## kvom (Oct 24, 2014)

gbritnell said:


> Leaving all the politics aside you are doing some outstanding work on this piece. I see in the one picture you have a threading die on a boss with an end mill in the center of it. What exactly was your machining step here?
> And as far as manual machines go, almost everything can be done on them given the time and ingenuity.
> gbritnell



If I had to guess, I think he was using the die to center the work.


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## Sixtysixdeuce (Oct 24, 2014)

> I see in the one picture you have a threading die on a boss with an end  mill in the center of it. What exactly was your machining step here?


The end mill was just still hanging out from cutting the profile.  I centered the quill over the piece and used slight down pressure of the quill on the die to keep it straight.

Did the same thing on the receiver extension, except in that case, I was going for 100% threads on a piece with only 0.070" wall thickness, so I also had a pilot down the hole to keep the piece from crushing.  Just so happened that a Craftsman 9mm deep socket was the exact .491" diameter I had the hole reamed to!



> Armed robbery is death sentence.



As it should be.  It certainly *can* be here.............if the victim is armed!  

Despite attempts by both sides to correlate gun ownership rates with crime, there is no actual evidence proving either case.   More guns  &#8800; more violence, nor do higher ownership rates show any causal effect with reduced crime.  Here in the US, we had the federal assault weapons ban in place from 1994-2004.  During that time, violent crime dropped.  But it had been falling for three years prior to the ban, and it continued to fall after the ban sunset, despite the rhetoric from the anti gun crowd that the streets would run red with blood if the evil guns were allowed to be sold again.  Today, the AR-15 is the most popular center fire rifle in the USA, literally hundreds being sold every single day.  Yeah, they've been used in a handful of high profile atrocities over the last decade, and absolutely villified by the ban crowd over said tragedies.  Fact is, though every life is significant, the mass shooting deaths are _*statistically*_ insignificant.  5, 10, 20 people being killed is a horrible thing, but we should not set public policy and attempt to restrict or take away the rights of millions over something that falls several decimal places to the right in a breakdown of causes of death.  It is also statistically insignificant and virtually unproveable, but very easy to make the argument that the ability to protect themselves with a firearm has _saved_ many more lives.  I know one gal personally who fended off a violent invader with a history of rape and murder. (our "justice" system and recidivism rates are wholly another discussion)

Truth is, crime rates trend independently of gun ownership rates and anti-gun legislation.  Socio-economic factors and demographics are where it's at.  It has been pretty well demonstrated the world over that banning them doesn't solve anything, and it's just as clear that huge numbers of them in private hands doesn't do all that much lot to deter criminals.  They're just tools.   They have no will of their own to do evil, and they are not talismans that protect against it.  Just pieces of metal, wood and plastic.

OK, rant off


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## Herbiev (Oct 24, 2014)

A guy here in Oz made some very high quality guns but as a couple found their way into a motor cycle gang the guy got a ten year jail sentence yesterday. The authorities are going crazy because there are still two more guns unaccounted for. 
The judge said that when he made the guns he should have known they would end up in unlicensed hands.


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## Sixtysixdeuce (Oct 24, 2014)

> The judge said that when he made the guns he should have known they would end up in unlicensed hands.



Not to derail my own thread, but yeah, the anti gun crowd has been using that post hoc argument for a long, long time.  Any reasonable person sees it for what it is; just as ridiculous as blaming the automaker, distillery/brewery, bar owner, etc. for a DUI crash.

People will use whatever weapons are available, including their own fists and feet (which, incidentally, are the weapon used in more USA homicides than rifles).  Perhaps one day our betters will learn that making more objects illegal (or making illegal objects _*more*_ illegal) does not reduce crime.  As for firearms specifically, yeah..........not rocket surgery to manufacture.  Yes, it takes some skill and equipment for a project like this, but $50 in your pocket, a trip to the hardware store and a youtube tutorial can have any idiot up and running with a single shot 12 gauge in a couple of hours with basic hand tools.  Like the Kyhber pass weapons; crude, but functional and deadly.


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## SixSixSevenSeven (Oct 24, 2014)

The way I see it. The intent to kill does not originate within the implement. A sane person will not be handed a firearm and instinctively shoot a person. At the same time a person who is set on murdering somebody else isn't going to be swayed by whether or not firearms are available, if firearms are available then they will use them, else they have a multitude of other implements available whether it be knife, poison, running them down in a car or even bare knuckle fighting.

I believe its the Czech republic which has some of the highest firearms ownership in europe, no issues with firearms crime at all.

To me. The intent to kill originates in response to social, political or economic issues.
The firearm is a block of metal, maybe accompanied with some wood and/or polymer. It doesn't go out and do anything on its own. It doesn't mind control the wielder.


I must apologise for continuing with the derailing. This truly is an amazing piece of machining. Just need to mould yourself some copies of whatever the latest "tacticool" accessory is for the budding mall ninja.


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## Sixtysixdeuce (Oct 25, 2014)

> Just need to mould yourself some copies of  whatever the latest "tacticool" accessory is for the budding mall ninja.


Hahaha.  A friend of mine runs an injection molding business; if I were inclined to build the mold, he'd run it.  Lot of work for a one-off, though; much easier to mill them out of ABS, acetyl or whatever else I have lying about.  That's how the grip was done, and how the stock and hand guards will be.  

It is going to get a faux 1:2 scale EOTech, which will be a remodeled micro red dot.  

I got the take down pins and gas key done today.  I was terrified of tapping the #2-56 holes in the bolt carrier, and justifiably so.  Snapped two taps off, had to carve the ends out carefully with an 0.058" carbide end mill.  Whatever this Taiwanese air hammer chisel was forged from, it's some really tough stuff.  Carbide is the only thing that gets through it decently, but I still snapped several PCB carbide drills trying to get those holes done.






The takedown pins weren't too bad, except cutting the 1/32" slot for the detent pins.  Killed another end mill on that part.  The detent pins & springs are from a wristwatch band spring bar.  Got the idea this morning, made a trip to the local jeweler, and grabbed a couple of 15 and 18 spring bars.  The 15 bars had just what I needed, with 1.0mm springs and pins.  

The takedown pins themselves were cut from #6-32 socket head screws.  Made life a little easier starting with something that had a head and was very close to my final 0.125" pin diameter.  The unthreaded shank on these 1-1/2" screws measured 0.136" before machining.


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## ejcheli (Oct 25, 2014)

This is good stuff!! I am a huge fan of firearms of all kinds, especially the AR15 having used one extensively in the military, and the .17HMR is one of my favorite calibers too. This project is bad ass man, keep up the good work!!

Eric


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## Omnimill (Oct 25, 2014)

- Sorry Thread hijack - nice avatar Eric! What is it an A10?


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## Sixtysixdeuce (Oct 25, 2014)

> What is it an A10?



Don't mean to answer for him, but yes.  You're looking at the business end of the flying tank and it's 30mm GAU-8 cannon.


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## Sixtysixdeuce (Oct 26, 2014)

Got the charging handle done late last night.  That ended up being a lot more work than anticipated, with a lot of careful fitting to get everything sliding smoothly.  about 6 hours all in.  I did goof a little and overran my numbers where the rear should be profiled to fit the horizontal cut in the receiver, but it will not affect function and is barely noticeable.  After what I went through, I'm not inclined to redo the thing right now.  The handle is also a tad thinner than scale; I didn't want to cut the receiver extension housing down any further, and a 4140 steel handle can be trimmer than an aluminum one.

The handle is cut from 4140 chromoly stock, the latch is spring steel, using a 0.041" drill bit for a pin and a 0.055" coil spring.  I only blued the rear of it, as the bluing will wear off wherever it contacts the receiver anyway.














http://i110.photobucket.com/albums/n117/Hunter2506/Machining projects/IMG_1206_zpsd478fb7c.jpg


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## ejcheli (Oct 28, 2014)

Omnimill said:


> - Sorry Thread hijack - nice avatar Eric! What is it an A10?



As Sixtysixdeuce confirmed, indeed it is! I love aviation and I often use the A10 avatar because I think its one of the most awesome jets ever made. What other aircraft is built around a gun as powerful as the AUG-8 Avenger!? None I tell you.

Now back to the topic at hand, what made the charging handle so difficult?

Eric


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## Sixtysixdeuce (Oct 28, 2014)

> what made the charging handle so difficult?


Very tough to clamp something that thin tightly enough to cut without crushing it.  This is also annealed 4140, so while tough, it will bend, which happened a couple of times when the cutter got a good bite, and when drilling through the front.

Remember, the bulk of the handle is just 0.200"x0.110", only 0.005" thick at the top and 0.035" on the sides.  There just isn't much there.  

Cutting the 0.040" slot for the latch was a challenge, and there was also a great deal of final fitting to get it and the bolt/carrier to move freely both together and independently in the upper.

I did get a stock made last night.  Just finished the adjustment lever & pin, but haven't uploaded a photo of it yet.

Shown with a Glock 20:


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## ejcheli (Oct 28, 2014)

Hahaha, that truly puts it into perspective, its tiny!! I love it. And seriously man, you are blowing my mind doing all of this without CNC!! I was going to say "well you could do...." but realizing that you are all doing this on manual machines... amazing job.

I do know that the hardest part of machining things, especially tiny things, is trying to figure out HOW to hold it, not so much HOW to machine it. Fixtures are everything and they take some ingenuity. Everything I do at work is usually measured to .0001" and most of the parts are no bigger than an 1.0" square so I understand your predicament.

Keep up the good work.

Eric


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## Sixtysixdeuce (Oct 28, 2014)

> I do know that the hardest part of machining things, especially tiny  things, is trying to figure out HOW to hold it, not so much HOW to  machine it. Fixtures are everything and they take some ingenuity.



Exactly.  And it's difficult to justify making special fixtures for one-off parts when I'm usually able to find a way to secure things pretty well for the tolerances I need to hold, which are nowhere near tenths.  Heck, I don't even own measuring tools that are accurate to <0.0005".  For most of the parts in this critter, up to 0.003" or 0.004" is acceptable, more in some places.  Really the only areas that need to be 0.001" or less are fire control parts, namely sear engagment and pins/holes. 

Also, since it _*is*_ a one of a kind, hand fitting is no big deal, sometimes easier than fussing with an indicator every single time the part moves in and out of vises or clamps.  

I did upload the latest photos this evening:


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## ejcheli (Oct 29, 2014)

That is very true! And as you say, its a one off part, its not a production model so its not really a big deal. Just like back in the day, guns were manufactured by hand and were custom fit together and one guns parts were not interchangeable with another, but they worked! 

So cool, I will be watching this thread with continued interest, as I want to make my own firearm someday as well. My shop has an FFL so we can make and distribute parts but as you said in your first post something about it being legal if for yourself? I am a big supporter of firearms but I didn't know about this. 

Found this on ATF website... so cool:

_"Firearms may be lawfully made by persons who do not hold a manufacturer's license under the GCA provided they are not for sale or distribution and the maker is not prohibited from receiving or possessing firearms. However, a person is prohibited from assembling a non-sporting semiautomatic rifle or shotgun from 10 or more imported parts, as set forth in regulations in 27 C.F.R. 478.39. In addition, the making of an NFA firearm requires a tax payment and advance approval by ATF. An application to make a machinegun will not be approved unless documentation is submitted showing that the firearm is being made for the official use of a Federal, State, or local government agency."_

So basically you can use up to 10 parts to make a firearm if you didn't want to build the whole thing? Similar to the 51% rule in aviation? The tax thing and approval from ATF kinda sucks but those are for Title2 stuff right? Title 1 can be 100% manufactured by anyone is isn't a felon and don't need to be checked or registered or anything. How awesome is that!?

Eric


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## petertha (Oct 29, 2014)

That's impressive sixtysix. Just wondering, is there a HMEM equivalent to the gun making/smithing world you hang out at or could recommend? I see so many youtube type vids where they are doing interesting machining & metalworking techniques... that all seem to be firearm projects of some ort (all aspects of machining, honing, grinding, heat treating, surface treatments, colorization...). There just has to be some useful resources there.


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## Sixtysixdeuce (Oct 29, 2014)

> So basically you can use up to 10 parts to make a firearm if you didn't  want to build the whole thing? Similar to the 51% rule in aviation?


You can use as many off-the-shelf parts as you want for any "sporting" firearm, and as may _*domestically*_ produced parts as you like in any firearm.  What that text refers to are provisions of section 922, which prohibit the importation of non-sporting firearms.  That is why you see some goofy re-works of rifles like the thumbhole stock Norinco AKs and the HK SL8, which is the importable version of the G36.  There are scores of folks who are in violation of 922(r), mostly because they didn't know about it, and started swapping out parts in their SKS or Romanian WASR AK.  It is not something that is heavily prosecuted; ATF just doesn't seem to care about the 19 year old kit who covered his Yugo underfolder in Tapco parts, but still has an import parts count of 11.

Simply put, if you are building a "non-sporting" firearm, such as a conventional pistol grip AK, AR, G3, CETME, FAL, etc, on a receiver YOU manufactured (legally, the receiver is the gun), then you must have 10 or fewer _*imported*_ parts (optics, lights, lasers, etc. are accessories, not considered gun parts).  Same rules apply if it is an imported receiver.  If it is a USA produced, _*finished & serialized*_ commercial receiver, however, the import parts count is irrelevant, as it is declared a domestic firearm.  That's the deal with the parts kits that are everything but the receiver; the receiver is non-importable (oftentimes because the receiver is a machine gun receiver, and even if you were to weld up the extra cuts & holes, ATF has the "once a machine gun, always a machine gun" policy)

If you are building a "sporting" firearm (basically an arbitrary, "lick your finger and check the wind" set of features ATF declared), then import parts count is irrelevant.



> The  tax thing and approval from ATF kinda sucks but those are for Title2  stuff right?


Yes, the $200 tax stamp applies only to title II NFA stuff (short rifles/shotguns, destructive devices, supressors, AOWs).  To make a title II weapon, you complete a form 1, get your local CLEO (sheriff or chief of police) to sign off, mail the form and a $200 check to NFA branch, then wait for approval (has been quicker lately, but was taking over a year at times).  The part about machine guns is due to the Hughs amendment to the 1986 Volker-McClure act, which prohibits the transfer of machine guns made after May 1, 1986 to private citizens.  That's why machine guns are so expensive these days; fixed supply, increasing demand.  There are somewhere around 174,000 transferable machine guns on the registry.  The only work-around is to become an SOT manufacturer, who can build and possess "post samples".  But being an SOT is not the same as being a "kitchen table FFL", and the machine guns must be transferred or destroyed if the license is not renewed or otherwise becomes invalid.



> Title 1 can be 100% manufactured by anyone is isn't a felon and don't  need to be checked or registered or anything. How awesome is that!?


It isn't just felonies; domestic violence conviction, misdemeanors that could have carried a sentence >12 months, being adjudicated a mental defect, having warrants or being a fugitive.  All the same stuff that's listed on the form 4473 when you buy a gun from a dealer.

But yes, if you can lawfully possess a firearm, you can lawfully build one for yourself.  You do not have to serialize it, and it _*is*_ legal to sell home builds; you just can't build them with the *intent* to sell.  Kind of a fuzzy line, but basically, the guy who sells a home build years after making it is in the clear, where the guy who bought and finished a 2 dozen 80% lower receivers, built them, and has been selling off complete rifles to generate an income is in violation of the law.

As for the 80%, again, ATF has kind of an arbitrary declaration of what constitutes 80%, but they are not legally a firearm until they are 81% or more complete.  That is why you see AR-15 80% receivers sold with no FFL requirement; they're legally a paper weight until you start cutting on them.



> Just wondering, is there a HMEM equivalent to the gun making/smithing world you hang out at or could recommend?


I think Practicalmachinist.com has a pretty busy firearms section, but otherwise I don't know of any boards.


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## ejcheli (Oct 29, 2014)

That is an astounding amount of information, thank you! I see gun projects in my future!


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## jj-smith (Nov 3, 2014)

Nice work Deuce,

Gets the blood warmed up and the desire going again.

We Canucks can't do much of that anymore up here. Our wise guys have made the working on our own weapons nearly impossible unless you are an approved gunsmith.
Even adding Tac stocks and such things are liable to get you no peace while out hunting or peppering the back 40. 
 We can have banana/AK mags but only if they're permanently plugged to allow for 5 rounds (except for the 22's), I guess 5 rounds won't kill anyone but a full mag will?

I gave up working on my own guns and ideas because anything you machine or alter is pretty much illegal.

I like the attention to detail and the long hours of work you're giving it, I will follow because of the quality I see going into it, and not least, I love the AR.

Very nice job! Regards, J.


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## Omnimill (Nov 5, 2014)

You're doing great but work faster, I can't wait to see this finished! Any chance of a video of it in action when it's finished?

Don't feel bad JJ, as I'm sure you know we have it really bad here in the UK, they even stopped us buying Airsoft guns unless you belong to a club...


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## Cogsy (Nov 5, 2014)

And here in Australia we can't own Airsoft guns at all. See, there's always someone worse off than you - normally it's me


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## Omnimill (Nov 6, 2014)

Gosh that is bad Al. Airsoft guns used to be easy to buy over here but the change in the law put many companies out of business. You can still buy them without joining a club but the choice is very limited and they have to be in bright colours like pink or blue!


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## Sixtysixdeuce (Nov 6, 2014)

Yeah..........draconian gun laws are the primary reason I could never live in those nations where you drive on the wrong side of the road.  

Back on topic, when I was cutting the hammer, I forgot to account for the 13/16" radius at the rear of the receivers, which puts the upper a little higher than the correct 1/2 scale 3/4" radius (impatience + damaged 3/4" collet), so the bolt carrier was not pushing the hammer down far enough to engage the sear or disconnector.  In an attempt to avoid remaking the hammer, we tried to TIG some material to the face of it.  Didn't pan out so good:






(not to self: 35 amps too hot for tiny pieces)

So, I gotta do that bit again, and I had killed my last 1/8" carbide cutter just before I blew a capacitor in the phase converter.  Lol.  Phase converter is back up and running, but my 10 pack of 1/8 cutters isn't here yet.  Plus some personal family issues have taxed my spare time and motivation lately.  But I'll get back after it soon.  Still got awhile before I hear back from ATF anyway, plenty of time to make everything besides the barrel.


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## Sixtysixdeuce (Dec 2, 2014)

Guess this thread is past due for an update!

Got a hand guard built a little while back.  I made the mistake of halving the Midwest Industries one I had on hand with no consideration for centerline to top of rail on my miniature upper, so the rail heights are mismatched 0.036", but oh well.

Also got an extractor and firing pin sorted out, although I need to revisit the firing pin, as the surface area of this one is too large to get ignition with the power the hammer has.  





After round two of smoking the smaller 230V 130 MFD cap in my converter a couple weeks ago, I ordered a pair of 330V 145 MFD units, which came in on Saurday.  I found a little time to tinker Sunday and yesterday, made the front sight and a faux barrel.  Still waiting on my letter from ATF, but at least it looks the part now.  I do have my .17 barrel, but still need to make or buy a chamber reamer before profiling it.

The sight still needs a little hand finishing, as well as pin holes, sling swivel and drilled/tapped for sight post, but is basically done.  Turned out to be a 6 hour piece.


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## MachinableWax (Dec 2, 2014)

Nice work!  Neat project.  

What was the ATF determination of what this classifies.  Did it pass as a pistol, or did they make you do AoW/SBR?



> Just wondering, is there a HMEM equivalent to the gun making/smithing world you hang out at or could recommend?


http://www.weaponeer.net/

A little slow on traffic, but there are plenty of friendly, skilled, and knowledgeable gunsmiths there.


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## Sixtysixdeuce (Dec 2, 2014)

> What was the ATF determination of what this classifies.  Did it pass as a pistol, or did they make you do AoW/SBR?



No answer yet.  Gubbermint agency, so I wasn't anticipating expediency..............


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## Sixtysixdeuce (Dec 9, 2014)

Still no word from ATF, but we're getting pretty close on the project.  All that really remains is the forward assist and the real barrel.  Dust cover is done, milled from 4140, as I didn't feel like machining dies to form it from sheet metal.  Also done are the flash hider, front hand guard retainer and one of the most tedious parts, the combination bolt catch and ejector.





















And one for scale:


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## ejcheli (Dec 10, 2014)

That is so cool. ;D


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