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

[Sixtysixdeuce]

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!

 

[Swifty]

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.

 

[Omnimill]

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

 

[gbritnell]

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

 

[gus]

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

 

[kvom]

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.

 

[Sixtysixdeuce]

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 ≠ 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

 

[Herbiev]

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.

 

[Sixtysixdeuce]

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.

 

[SixSixSevenSeven]

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.

 

[Sixtysixdeuce]

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.

 

[ejcheli]

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

 

[Omnimill]

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

 

[Sixtysixdeuce]

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.

 

[Sixtysixdeuce]

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

 

[ejcheli]

- 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

 

[Sixtysixdeuce]

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:

 

[ejcheli]

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

 

[Sixtysixdeuce]

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:

 

[ejcheli]

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