How do I heat treat an AK receiver?

[kymasabe]

If I buy a flat receiver and bend it myself, how do I heat treat it? I guess I could look in the phone book for a someone semi-locally who does that sort of thing but is it possible to heat treat it myself?

[hoytinak]

The ejector on the left lower rail also needs to be hardened. Since most finishes that you will apply to the completed firearm will require that it be baked at 400 degrees or more we will only concern ourselves with spot heat treating the FCG holes and the ejector. The hammer and trigger pin holes on both sides of the receiver need to be hardened due to the amount of stress they receive during the life of the rifle.

You will need the following:
MAPP gas torch
Sand paper
Pliers
Pail of water
Work Gloves

There are two steps to heat treating metal for an AK receiver. The first is to harden it by taking it up to 1500 degrees F and then quenching it. This will make it very hard but also very brittle. The second step is to temper it by taking the metal up to 800 degrees F and letting it air cool. MAPP gas will heat the metal to the proper temperatures in a reasonable span of time. The way to gauge the temperature of the metal is by color. When the metal gets to a bright glowing orange/yellow it is time to quench it in the pail of water. Sand the treated area to bare metal and reheat it until it is a gray/blue. At this point set it aside to air cool. Do the ejector (Left lower rail) first to get a feel for the process.

You will also need to heat treat the hammer and trigger holes (FCG). These are the pivot pin holes located on both sides of the receiver. Heat and quench each hole and then temper them individually and let them air cool.

[dipper]

Being a tool maker, I have heat treated countless pieces of steel in all types, grades, and configuration---for many different applications.
I would not heat treat a receiver for any firearm as hoytinak describes unless I lived in a third world country with no access to proper methods and my life depended on me having anything that would fire a few rounds.
Heat treating is a very critical process often overlooked by people who do not know what they are doing or have little knowledge about the subject.
Harding temp. and annealing temp depend on what steel you are using and some steels require fairly strict adherence to temperatures and times.
I am sure that in some places in this world, someone has built AK's as described by hoytinak but it is not necessary here in the US---there are MANY heat treating business's out there that can do it properly and for minimal costs.
Keep in mind that any part of a firearm that is to soft or to hard can be a big problem.
Also, keep in mind that you never know on which round something could let go---could be on the 5th or 500th round---no way to tell.

[kymasabe]

Someone told me today to heat the receiver to cherry red and quench it in a bucket of water. Would make it hard but brittle. Next step was to immerse it in a metal tray full of brake fluid, put the tray in my grill, light the brake fluid, and let it burn until the brake fluid is consumed, was told it would take 1/2 hour or so and the receiver would be good to go after cleaning and painting/finishing. Sounds a little too easy to me.

[hoytinak]

I am sure that in some places in this world, someone has built AK's as described by hoytinak but it is not necessary here in the US

Myself and several buddies have built around 50 AKs total over the past 10 years using this method and we've never had any problems with it....and yes, we're all in the US. ;)

[dipper]

Good for you hoytinak---not trying to be a jerk but it IS NOT the proper way to heat treat a receiver.
Glad to hear you and your friends haven't had any problems----YET!!;)
If you are making them for sale, or have sold any----assuming you have a manufactures license---I hope you have your liability insurance paid up---you may need it.
You are permitted to manufacture a rifle for your own personnel use without a manufacturers license---ya' all must have a pile of AK's!!---but I don't think you can transfer ownership or sell one without a license.
Also, if you shoot on any public ranges and something happens to the guy next to you you're in a world of hurt.

[kraigwy]

I think this comes under the heading of:

DONT TRY THIS AT HOME

[Swampghost]

I spent many years as a machinist. The co. that I worked for contracted with many aerospace and defense suppliers. Heat treating is NOT a DIY project when it comes to something that could literally 'blow up in your face', it's a job for pro's. They will do a Rockwell test and provide you with certification to CYA. Bear in mind that YOU are now becoming a 'manufacturer' and will be responsible for any problems that occur down the line.

Say that you decide to sell the piece or falls into someones elses hands by whatever means and some handloader overstuffs it, it blows fragments back and the new owner is blinded or worse, YOU will be held responsible. Telling a court of law that you heat treated the part according to some BS that you got off of the web will not fly very far.

I'm with dipper ATW and it really doesn't cost much to have it done professionally.

[hoytinak]

I didn't say it was the best (of course it's better to have it done by a pro) but it's a way to do it yourself (as the OP asked for).

[Jimro]

The mild steel that most people use for AK receivers is pretty damn hard to screw up. As far as heat treating by color, it isn't as sexy as a digitally controlled kiln, but it works.

Catastrophic failure is just as likely to come from impurities in the metal blank put there long before anyone ever decided to turn it into a receiver.

If you want to Cover Your A$$ then building an AK is probably not for you.

And as far as tempering steel with an open flame, that's how Colt finishes the barrels for M4 carbines. It's old as dirt tech, but it works.

Jimro

[TheManHimself]

What I've learned from The Firing Line today:

One of the advantages of the AK is that it can be cheaply manufactured with 19th-century metalworking technology by smelly bearded men in third world countries and still works forever without failing; however, if this method of construction is attempted by American citizens the rifle is extremely dangerous and prone to explode at any minute.

:D

[dipper]

Can't agree with ANYTHING you said Jimro.
In over 30 years of tool making, I have seen guys screw up the most simple of tasks and I have worked with hundreds of people in the machining industry at all levels of experience.

"Catastrophic failure is just as likely to come from impurities in the metal blank put there long before anyone ever decided to turn it into a receiver."

Total BS

"If you want to Cover Your A$$ then building an AK is probably not for you"

More BS
If your saying that encouraging someone WITH NO EXPERIENCE to do the job right makes building an AK " not for you", well......
I didn't see the mention of a Rockwell Hardness tester anywhere in the "how to" description either----which beats the hell out of " hit it with a file".


"And as far as tempering steel with an open flame, that's how Colt finishes the barrels for M4 carbines. It's old as dirt tech, but it works."

What does that mean??
Many companies use that technique for annealing parts so what??
You can bet your butt that it is a very well controlled process with the temperature, time, and atmosphere tightly controlled-- it ain't like some guy out in the garage with a blow torch.
AND I'll bet that every so many parts are hardness checked and certified.

If you think telling someone with no experience to grab a torch and have at it is a good idea, well.......

Rifle receivers ain't washers or spacers---they are something that can hurt you---and INNOCENT people around you.
I just can't sit back and let someone tell someone else to do something like that---especially someone with no experience.

[dipper]

What I've learned from The Firing Line today:

One of the advantages of the AK is that it can be cheaply manufactured with 19th-century metalworking technology by smelly bearded men in third world countries and still works forever without failing; however, if this method of construction is attempted by American citizens the rifle is extremely dangerous and prone to explode at any minute.



Then you need to re-read what has been written and try to comprehend what was said better!!:)

[hoytinak]

One of the advantages of the AK is that it can be cheaply manufactured with 19th-century metalworking technology by smelly bearded men in third world countries and still works forever without failing; however, if this method of construction is attempted by American citizens the rifle is extremely dangerous and prone to explode at any minute.

Kinda funny, that's what I was thinking myself. :)

[Swampghost]

I know, we used to oil and water treat as well as anneal our own parts but they weren't as critical as parts for a firearm.
We machined the actions for the 30 mm GAU-8 used in the A-10's and the M 134 Miniguns. They went out for heat treating and final grinding.

[DnPRK]

dipper, I take it that you have no familiarity with AKs or else you wouldn't post what you have posted.

An AK is not a Remchester. The trunnion of a AK is a machined and classically heat treated part that serves the same function as the receiver ring and lug bearing surfaces of your Remchester. In other words, the trunnion takes the stresses and has to be heat treated for strength. The trunnion is riveted into a thin, mild steel, formed sheet metal receiver. The AK receiver is not a load bearing, stressed part. Spot hardening of the sheet steel receiver is needed at the locations posted by hoytinak to prevent peening of the fixed ejector and elongation of the hammer and trigger pin holes.

When the Soviets first started making AKs, they tried heat treating the stamped receivers like you would a Remchester and had many failures. The thin receivers would warp to the point of being useless or crack from being too brittle. They reverted to use of machined receivers until they got the spot heat treatment scheme worked out.

BTW, spot heat treating is not foreign to US manufactured firearms either. One example of spot hardening is the slide of the 1911A1. An example of spot annealing is the heel of the M1 Garand.

[Swampghost]

Pie fight here!

[BeCoole]

The only reason you heat treat an AK receiver is for wear resistance.
As pointed out above, it does not bear any load.

You heat treat the ejector so that it doesn't get peened by the ejecting steel cases.

No need for rocket science with this.

[dipper]

DnPRK---Your right, I have limited ( some) experience with AK's BUT, Your wrong---EVERYTHING I posted still applies and I think you are missing my point/points entirely.
I have made a "few" firearms related parts however and have talked with a few firearms designers and engineers.
First, I have been told by these engineers and designers that NO PART used on any firearm can be out of spec for hardness that's NO PART.
It doesn't matter if it is in your words "The AK receiver is not a load bearing, stressed part."
It STILL has to fall within specs for hardness----JUST LIKE a set of rings and bases do on a bolt rifle or a lever on a lever action etc. etc.---they are not a "stressed" part, but they CANNOT be out of spec for hardness---like 58-60 Rc.
That would be to hard and NO part on a firearm can be out of spec and be to hard------NO Part.

SO, again, here is a guy ( the OP ) with no experience, no rockwell tester and are we suppose to say " grab a torch" ??

Do you think AKs are spot hardened with a torch??

Let me ask you this, can you reliably "spot harden" a hole with a torch??
I mean a hand held every day common in your garage set-up??

"
When the Soviets first started making AKs, they tried heat treating the stamped receivers like you would a Remchester and had many failures. The thin receivers would warp to the point of being useless or crack from being too brittle. They reverted to use of machined receivers until they got the spot heat treatment scheme worked out."


Yep, but we don't have that trouble today, we can heat treat some very thin parts with very little warping.
And the machined receivers were/are machined out of pre-hard.

"
BTW, spot heat treating is not foreign to US manufactured firearms either. One example of spot hardening is the slide of the 1911A1. An example of spot annealing is the heel of the M1 Garand."

No Kidding!!:)
Why I never did knew/did that before!!
Thanks for the heads up!!:)

Point is, AGAIN, if you or anyone else thinks it's a good idea for someone with no experience and that doesn't have what he needs to check the hardness to wing it ---that's up to you.

My arguement is NOT how a AK receiver is made or what the factories do---it's suggesting that a rookie can accomplish safe specs with his torch---I say there is a GOOD chance he can't---and I will not recommend it.

Nuff said on this!!

[BeCoole]

Tempsticks :)

[Jimro]

Dipper,

If you don't agree with anything I say I guess I need to go cry in a corner or something.

I shoot two AK's with home bent receivers. I give you permission to gloat when one of them blows up and kills me.

Jimro

[1SGT Harlin]

Listen U jabroniiies,
The AK was designed to be built my 3rd world pheasants. As I live near Detriot I know was the 3rd world looks like. As yes, you can heat treat an AK at home. I would use temple sticks to control the temp but, yes a regular MAPP would work fine. I'd quench it in used motor oil myself

[Swampghost]

1SGT, you DO realize that your statement opens you to litigation if something blows up? Yep, it's the web and you may feel somewhat insulated but even a dummy like me can get your IP. Lawyers can do better.

[Bill DeShivs]

I hand make a lot of springs, and I do it with a torch. I'm pretty damned good at it-no failures in about a thousand springs. Here is something you don't realize- you can not "spot harden" anything. For carbon steel to be hardened, it must be heated to the proper temperature and quenched, so you would have to harden the entire receiver, then temper it back-or it will be very brittle. You can't do this in "spots."

[dipper]

+1 Bill

[Jimro]

I hand make a lot of springs, and I do it with a torch. I'm pretty damned good at it-no failures in about a thousand springs. Here is something you don't realize- you can not "spot harden" anything. For carbon steel to be hardened, it must be heated to the proper temperature and quenched, so you would have to harden the entire receiver, then temper it back-or it will be very brittle. You can't do this in "spots."

actually, you can.

http://en.wikipedia.org/wiki/Differential_hardening

Jimro

[popeyespappy]

As I live near Detriot I know was the 3rd world looks like.

Yea but 3rd world or not Detroit probably has more heat treat facilities per capita than any place else on the planet. Timken probably has a furnace operator living on every other block. So if you live in the Detroit area you probably know some one who can take your home bent flat to work with them and toss it in the batch furnace with a load of car parts.

[bejay]

if your building on a flat a torch used on the hammer and trigger holes and ejector is common probably almost all of the home made flats built into a receiver do not do anything else other than maybe using kasenit to get the surface a little harder in lower carbon steels. even receivers you buy from a manufacturer may not be fully hardened depending on the manufacturer.
this is sheet metal that is only around .040 thousands thick there is very few places that can harden the whole receiver without ending up with a warped paper weight.
however if your worried about it guess you could just buy one already made there not that expensive if you dont have the jig to bend a flat along with a welder for installing rails it is usually alot cheaper to just buy one from a manufacturer already done.

[MaxHeadSpace]

Not sure if this got mentioned. I'm not wading through the thread --

Building a receiver is viewed as "firearms manufacture" and requires licensing from the BATF.

If you think heat treatment opens a can o' worms, wait until you talk to the boys in the federal building about manufacturing AK recievers. :eek:

[Bill DeShivs]

Jimro
Yes, you can differentially temper knife blades. I have made "a few" of them, but you can only differentially SOFTEN, not harden parts.
You could leave the receiver too hard and soften a few spots on it-but that would kind of defeat the purpose, wouldn't it? You can't adequately do spot heat treatment at home.
Maxheadspace
Anyone can manufacture a regular firearm for their own use. It's perfectly legal.

[MaxHeadSpace]

Anyone can manufacture a regular firearm for their own use. It's perfectly legal.

You can't manufacture a receiver, not without a license.

You can build a firearm from existing receivers, but you can't manufacture a receiver without a license.

From NRA:

http://www.nraila.org/Issues/factsheets/read.aspx?ID=70

Federal Firearms Licenses


The Gun Control Act, as amended by The Firearms Owners` Protection Act of 1986 (P.L. 99-308), requires that persons engaged in the business of dealing in, manufacturing, or importing firearms, or manufacturing or importing ammunition, obtain a Federal Firearms License (FFL). The federal firearms licensing system is administered by the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE), an agency of the U.S. Department of Justice.

---------------------
The Gun Control Act of 1964 requires that a gun reciever be identified with a serial number and that the serial number be registered and licensed by the US Govt. And you can't do that without being licensed.

[JohnKSa]

The Gun Control Act, as amended by The Firearms Owners` Protection Act of 1986 (P.L. 99-308), requires that persons engaged in the business of dealing in, manufacturing, or importing firearms, or manufacturing or importing ammunition, obtain a Federal Firearms License (FFL). The federal firearms licensing system is administered by the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE), an agency of the U.S. Department of Justice.You can make them, you just can't make them with the intent to sell them.

Making your own gun is fine. Being in the business of making guns requires the proper licensing.The Gun Control Act of 1964 requires that a gun reciever be identified with a serial number and that the serial number be registered and licensed by the US Govt. And you can't do that without being licensed.It's the Gun Control Act of 1968 (http://www.atf.gov/pub/fire-explo_pub/gca.htm) and it doesn't say that.

Here's a pertinent bit of information from the BATF's FAQ

http://www.atf.gov/firearms/faq/faq2.htm#a6

(A6) Does the GCA prohibit anyone from making a handgun, shotgun or rifle? [Back]

With certain exceptions a firearm may be made by a non-licensee provided it is not for sale and the maker is not prohibited from possessing firearms. However, a person is prohibited from assembling a non-sporting semi-automatic rifle or non-sporting shotgun from imported parts. In addition, the making of an NFA firearm requires a tax payment and approval by ATF. An application to make a machine gun will not be approved unless documentation is submitted showing that the firearm is being made for a Federal or State agency.

[SigfanTN]

To the OP: there have already been methods posted, here is a link:

http://www.surplusrifle.com/ak47/index.asp

If you look to the right side bar and read the Soup to Nuts articles, there is a step-by-step of how he is heat treating the receiver.

<disclaimer>I have zero first-hand knowledge of the process myself, so this link is posted for strictly information purposes in response to the OP</disclaimer>

[Bill DeShivs]

The information in the link is very erroneous. Rockwell 90 is not attainable on gun steel. That's 90% as hard as a diamond. Gun steel will not achieve 60 rockwell. When separately hardening the holes, you are annealing the hole next to it.

[Jimro]

Yes, you can differentially temper knife blades. I have made "a few" of them, but you can only differentially SOFTEN, not harden parts.
You could leave the receiver too hard and soften a few spots on it-but that would kind of defeat the purpose, wouldn't it? You can't adequately do spot heat treatment at home.

Why don't you try the technique yourself? You obviously have the means to buy a receiver flat and make the attempt to selectively harden holes and ejector. At most you'll be out a few bucks and you'll get the opportunity to talk from experience.

Jimro

[dipper]

Bill is 100% correct, there are NO steels used in gun making that can obtain anywhere near 90-95 Rockwell---the dude is full of beans---it is IMPOSSIBLE.
He may have known that if he had one of those new fangled rockwell testers.

Bill is also correct about spot hardening the holes---anytime you put heat to one spot of any metal, you are also affecting the surrounding metal---to what degree depends on how hot your flame is and for how long you apply the heat.

[bejay]

I agree rockwell 90 is wrong and you are not going to spot harden and get uniform hardness, but that isnt the point it is to make the holes and ejector harder than the state they come in as a flat, there have been a few failures with wear or cracking from the holes either being to soft or to hard but for the most part it does work in preventing the holes from elongating at the fire control group pins and the ejector from mushrooming or deforming from shell cases slamming into it every cycle, and there is plenty of aks built on a flat with enough rounds through them to prove it.

[Jimro]

Dipper,

HRB 90 is a lot different from HRC 90.

Jimro

[dipper]

Jimro the guy said:

"This metal has been hardened to around Rockwell 90."

He doesn't specify what scale---in the gun industry---at least everything that I have been exposed to, Rockwell C scale is used as the norm.
If you are going to put things on the net, especially related to firearms work, you should be specific.
Just another indication that the guy leaves something to be desired IMHO.:)

[Jimro]

Dipper,

I agree, most firearms manufacturers use the Rockwell C scale. This is because between HRC 30 to HRC 40 is where most manufacturers want their receiver steel. Bolt steel is usually slightly harder. But take a look at an old Mauser action, they were case hardened so a Rockwell reading isn't going to accurately portray the toughness of the action, only the surface wear resistance, except on actions that weren't uniformly carburized where you'll get different hardness readings based on different test areas.

But talking bolt action rifles has pretty dang little to do with rifles designed to be made from stamped sheet metal.

Jimro

[Bill DeShivs]

Jimro
Why don't you send me a flat, and I'll experiment with it?
I doubt that I can spot harden it, and I'm pretty darned handy with things like that-but I'll sure try. But someone with no experience and a propane torch? I doubt it.

[darkgael]

Great thread to read through. I don't know enough about heat treating to comment. I do know that, being color-blind, the do it by color method would be a problem.
I do take issue with a comment repeated a couple of times: "One of the advantages of the AK is that it can be cheaply manufactured with 19th-century metalworking technology by smelly bearded men in third world countries and still works forever without failing"
It's the part about the "works forever without failing".
That comment is based on an assumption that is pretty much impossible to verify. The assumption is that those AKs are of the same quality and as safe as the ones that come out of the military factories (ie - the ones WE buy). Are they? You can't know that one way or the other. There may well be a quite high failure rate; we can't know that either. There are no safety statistics from the mountains of Afghanistan about the safety, durability, functionality of "home built" AKs.
Pete

[Chui]

Remind me never to purchase an AKM from some people who visit this board.

:p

Just take it to someone who has a company that specializes in this. Those in the Detroit Metro Area and Southern California will have no problems finding someone who does this. Obviously, in CA one cannot have the receiver, but that's another story.

Yes, Detroit is closing on "Developing World" status... as is the rest of the nation - and then the rest of the world follows.

[popeyespappy]

Just take it to someone who has a company that specializes in this.

Specializes in heat treat or home grown AK's?

[Chui]

Specializes in heat treat or home grown AK's?
Heat treating ferrous alloys. Sorry about the ambiguity.

[ISC]

As others have noted, the only part of an AK reciever that gets hardened is the ejecter and holes where the pins contact them. I would never consider hardening and tempering a bolt or trunnion, but the reciever just isn't as crucial as those parts. The technique described by Hoyt is perfectly valid and is better than is done by many of the less reputable AK manufacturers.

Building AKs isn't rocket science. Some of the snobs in this board just can't get it through their head that sometimes perfect isn't required; good enough is all you need.

Who carries around a torque wrench to make sure that their tires are properly torqued when they change a flat? no one. Sure, occasionally someone may not tighten up their lugnuts enough, but guestimating and hand torquing the lugnuts is good enough.

I wonder if some of the most vocal objectors would wait on the side of the road and wait for a professional to change their tire for them if they had a flat?

[dipper]

Are these just your thoughts ISC??
Or do you have the experience and knowledge to back it up??
Are you a Machinist, Tool Maker, Engineer ??
Ever actually do any heat treating?
Ever see anything fail because it was to hard and brittle? I have---some with some severe results to those close by.
Done ANY work for the firearms industry??


Don't understand why you would call someone who cautions a rookie to do the job correctly a snob.
Yeah, sometimes good enough is fine--- for boat paddles, paint jobs, etc.---not for firearms.

Has nothing to do with being a snob---more a question of safety.
HEY, I bet you're the kind of guy that yells " YA' ALL WATCH THIS" LOL:)

[darkgael]

"The AK was designed to be built my 3rd world pheasants" (by 3rd world peasants?)
Is that true? Was that one of Mikhail Kalashnikov's design parameters?
Pete

[ISC]

I wouldn't call myself an expert.

I've only built a few AKs, and the education I recieved in Nuclear Power School was focused more on heat transfer theory and reactor physics than materials.

When I started my undergraduate work as a Mechanical Engineering major, firearms wasn't even discussed, and the tens of thousands of rounds I've fired don't mean that I am a firearms expert.

After I left college and went to work as a millwright in power plants, paper mills, and industry the jigs and tools I made were only used on the jobs I worked on or ran; I never sold any of them or paid to have a stress analysis done on them.

I have seen items break that were improperly heat treated, but they weren't done by me. I know enough to know what is a critical part and what isn't. I know the inverse relationship between strength and hardness.

I've spent more time working with molten metal and welders than most men have spent deiving their cars.

I would never say I am an expert. Of course I never designed tires or worked at a tire shop, but I feel perfectly competent to change a flat tire.

[Jimro]

Bill, I'll check to see if I can't dig you up a flat. But try to do the heat treat process with a MAPP torch instead of propane.

Jimro

[blume357]

My real response was going to be "Good Lord did the internet lawyers come out...but then I realized just as many machinest showed up too"... the original question was for how to do it yourself and is the reason I opened the post... i've had a couple AK receiver flats laying around for a while along with at least enough parts to make one rifle...

First extended question... I was told by my father to imerse the hot metal in oil too... just kind of trying to figure out which is best...

second question...how do you stamp all those Rivets together just right?

[Bill DeShivs]

Jimro
I have air/acetylene.

[hoytinak]

First extended question... I was told by my father to imerse the hot metal in oil too... just kind of trying to figure out which is best...

Not sure which is the best as I've only used the method I posted earlier.

second question...how do you stamp all those Rivets together just right?

Some people have modified regular bolt cutters (just google it I'm sure you can find it). I tried the rivits on my first built and it was a PIA, so I started tapping the front and rear trunions and putting them together with screws.

recommended screw sizes
front trunion: 10-32 x 1/4
rear trunion and cross member: 10-32 x 3/8
rear of trigger guard: 8-32 x 1/4
front of trigger guard: 8-32 x 3/8
hex nut for trigger guard: 8-32 x 1/4

[dahermit]

First extended question... I was told by my father to immerse the hot metal in oil too... just kind of trying to figure out which is best...Depends on if it is water hardening steel, or oil hardening steel. Or, if it is high alloy steel (some require a sub-zero(liquid nitrogen) quench to properly harden). Or the steel may be a chrome-moly steel as a lot of gun steels are nowadays. It is unlikely that it is just water hardening plain carbon steel...they are not making much of that anymore.
Also, note that if it was water hardening steel...that really means brine not water...water will boil (form bubbles) as the steel is immersed, insulating where the bubbles are, leaving soft spots. The salt keeps that from happening. Furthermore, if it is high carbon, water hardening steel, and you quench it, it has to be drawn (tempered) immediately or if left for a period of time can produce fracture cracks.
If it is water hardening steel and you use oil to quench, it will not harden properly.
Also, keep in mind that professional heat treat shops do not use hand-held torches to heat threat...they put things in H.T. ovens that have thermostats that insure the proper temperature.
In short, if you are not a metallurgist, leave it the hell alone and stop listening folk tales about metal hardening from persons who have not been educated in the field...no matter how long they have been doing it. I have been breathing for 65 years and I still do not know anything about the respiratory system. How long a person has been doing something is a foolish defense for bad practices.

[MaxHeadSpace]

Manufacture -- as in "fabrication" of a firearm receiver is regulated by the BATF.

You can assemble guns from parts until you're blue in the face. The restriction is that you can't "manfacture" or otherwise configure an NFA firearm from a pre-existing receiver.

http://en.wikipedia.org/wiki/Gun_Control_Act

The Gun Control Act of 1968, Pub. L. No. 90-618, 82 Stat. 1213 (also known as GCA or GCA68, and codified as Chapter 44 of Title 18, United States Code) is a federal law in the United States that broadly regulates the firearms industry and firearms owners. It primarily focuses on regulating interstate commerce in firearms by generally prohibiting interstate firearms transfers except among licensed manufacturers, dealers and importers.

Marking Requirements

The law also required that all newly-manufactured firearms produced by licensed manufacturers in the United States and imported into the United States bear a serial number. Firearms manufactured prior to the Gun Control Act remain exempt from the serial number requirement. Defacement, alteration, or removal of the serial number (if present) is a felony offense.

--------------------------

Here's the legal Catch-22: You can't put a serial number on a receiver you've fabricated yourself without engaging in "defacement" or "alteration" of the serial number. And you need to be licensed in order to fabricate a receiver.

Otherwise, with an existing receiver, you can pretty much do what you will, so long as the serial number is left intact.

Trust me on this one. I didn't just fall off the turnip truck with respect to BATF regs.

[musher]

Trust me on this one. I didn't just fall off the turnip truck with respect to BATF regs.

Perhaps, but you are not correct, nonetheless.

(A6) Does the GCA prohibit anyone from making a handgun, shotgun or rifle? [Back]

With certain exceptions a firearm may be made by a non-licensee provided it is not for sale and the maker is not prohibited from possessing firearms. However, a person is prohibited from assembling a non-sporting semi-automatic rifle or non-sporting shotgun from imported parts. In addition, the making of an NFA firearm requires a tax payment and approval by ATF. An application to make a machine gun will not be approved unless documentation is submitted showing that the firearm is being made for a Federal or State agency.

[18 U.S.C. 922(o) and (r), 26 U.S.C. 5822, 27 CFR 478.39, 479.62 and 479.105]

source-- ATF Firearms FAQ (http://www.atf.gov/firearms/faq/faq2.htm#a6)

[Candiru]

AK receivers don't require a great deal of finesse to work reliably. The receiver has nothing to do with containing pressure--that's the front trunnion and bolt, both of which, if assembled from a parts kit, will have been heat-treated in proper facilities. The purpose of heat-treating the trigger and hammer pin holes is to add a bit of strength to the area in order to prolong the time until it's necessary to demill the gun and build a new receiver. The torch method is pretty crude and certainly not the best way to do it, but it seems to provide some benefit. The way some people are talking, heat treatment didn't exist before electricity and thermostats. (I know it wasn't as reliable or effective as it is nowadays, but it worked often and well enough to justify the time and effort.)

[Bill DeShivs]

Max-
In case you haven't noticed, we aren't talking about an NFA receiver.....or turnips.

[JohnKSa]

The restriction is that you can't "manfacture" or otherwise configure an NFA firearm from a pre-existing receiver.This also is not correct. You can make an NFA firearm as long as it isn't a machine gun and as long as you pay the tax and get BATF approval.

However, as pointed out, this thread is not about NFA firearms.Here's the legal Catch-22: You can't put a serial number on a receiver you've fabricated yourself without engaging in "defacement" or "alteration" of the serial number. And you need to be licensed in order to fabricate a receiver. You're making this too complicated. Putting a serial number on a new receiver is not defacing or altering the serial number since you are the manufacturer. And while you are not a licensed manufacturer, you CAN still manufacture firearms for your own personal use subject to some regulations.

[blume357]

don't hold any pressure was exactly what I was thinking... the worse that is going to happen if the mentioned part is not treated right is the holes wear out. The rifle is not going to blow up.

You metal guys remind me of myself and my peers... I'm a chimneys sweep and not only clean but inspect and repair chimneys. I've probably met about two homeowners/woodburners in my business (over 25 years) who have a grasp of how to properly install and operate a woodstove and this isn't nearly as complicated as metal work.

[deeppurple]

Dipper forgot that in the USA the first criteria for any business is to get profit, to cheat customer without giving a real product. They don't know even what and how to do.
That crap that he is talking about works for M16, which needs the awful feature to help pull the round into the barrel, ha ha.
AK is top of the line in design, features and exploitation.
At the factory the receivers are spot quenching.
Good luck.
It's never late to learn

[madmike]

The reason an AK receiver should ideally be treated completely is strength. Rolled and annealed 4130 has a tensile strength of 80,000 PSI. Properly heat treated, it approaches 225,000. This makes your AK much less likely to ding, bend or warp when you jump out of the truck the Chechen rebels are blowing up. It's far less critical for a recreational shooter. As noted, the trunnion is the critical stressed component, the receiver merely holds things together. This is why in the far, distant future, materials like aluminum and plastic will be used for receivers and frames. </sarcasm>

Treating the entire receiver is easy, with a jig that holds the receiver to shape, and a heat treating furnace. The holes will have to be milled after the fact, though, unless you have a jig with indexes for each of them, and then finish ream.

Pretty much every set of instructions I've seen online are crap. You don't triple heat and quench then red heat and air cool. You don't heat white hot. There is no Rockwell 90 on the C scale as far as steel goes (which almost never breaks 65, and even TiN and other exotic coatings rarely reach 90).

However, it is absolutely possible to differentially treat steel. The Japanese perfected several ways of doing this a millennia ago, as did the Franks and Norse.

A small, hot spot of MAPP on the axis pin holes, followed by a good dousing in water, light oil, or even sprayed rapidly with WD40 will provide appropriate hardness. You can judge temperature with a color monitor, heat sticks, by eye with experience, or by the field expedient of a magnet--when the metal austenizes, the magnet will stop sticking. After treating each hole, the receiver can be placed in an oven and heated to 500 for an hour, which will relieve sufficient stress on thin stock such as this, with a Rockwell C around 45. You can also torch temper, as long as you are quick on the color change. Quenching during temper is not ideal, but isn't going to matter much on something with the slack tolerances of an AK. And before any "experts" tell me I'm wrong, I do, in fact, have access to a Rockwell tester. I've been forging and heat treating blades, and some firearm parts, for 26 years.

The holes are far enough apart that if you're quick and steady, the heat bleed does not reach the other holes.

These holes need sufficient strength to slow them from egging out from friction, though obviously, nothing lasts forever.

As noted, this is not ideal, but if done properly, is perfectly safe and adequate for a weapon not expected to see heavy combat use. If you doubt your ability to do this, or to rivet properly, or to ream axis pin holes, or headspace, or time, then, as with any technical task, such as tuneups, brakes, alignments, water heaters, furnaces, wounds, computers, axes, tractors, etc, seek a professional for advice or to do it for you.

For the strongest in AK receivers, seek out the 1.5 mm (.064) Chinese receivers, or the milled receivers.

Edit: FYI, combloc AK receivers were completely heat treated. You can tell this when you have to bend, rip and force the old sections off the trunnions. They're a soft spring temper, probably around Rockwell 45-48.

[Willie D]

deleted

[LHB1]

...

[63chuck]

Marinate for three hours in ATF in freezer. Immediately place in microwave on MEDIUM for 22.50 minutes. Start shootin