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1/25/2018 7:38:29 AM
Posted: 5/12/2003 2:33:03 PM EST
Does anyone know the alloy of the AK47 flat receiver stamping offered by "FAC". It seems to me I read a post that FAC was associated with Hesse and this was most likely a unfinished Hesse receiver.I called FAC and the Lady told me she did not know but would have someone call me back ( never happened ).
Link Posted: 5/15/2003 3:38:57 AM EST
[Last Edit: 5/15/2003 3:39:49 AM EST by mg34ss]
As far as I know, you are correct. Hesse blank. I have no idea how they bent that blank, but from my experiance you have a one in 50 chance of getting the bends right. There has never been a worse deal. I have never seen one successfully built into a gun. Get a folded blank if you want to make your own. I think its 4130.
Link Posted: 5/15/2003 8:34:39 AM EST
Thanks for the good advice MG34.
Link Posted: 5/22/2003 6:59:41 AM EST
"FAC" did at last call back alloy is 4140
Link Posted: 5/24/2003 7:01:58 PM EST

We came up with a protype bending jig that will correctly get the bottom bends in right. Two of three of the flats we bent turned out right. The part we don't have "clean" yet is the upper lips. That was done by clamping a bar behind them and using a hammer to bend the lips down over the edge of the bar as a guide. They ended up looking a bit funky, but that does not show unless the topover is off.

As for getting the barrel on and off the trunion, we heated up the trunion instead of using a press, but we are still working on a short throw mechanical press to make the whole package something of a do-most-of-it kit.

The other bonus is that the same tooling could be used to produce the bent metal reciever blanks out of 4140 flat steel.
Link Posted: 5/25/2003 9:15:51 AM EST
Hi Osi,
are you doing any heat treating after forming?
Link Posted: 5/25/2003 6:07:05 PM EST
OK, guys, it's getting down right dangerous here. Bending the upper lips over with a hammer will stretch the upper lip and warp the sides of the receiver. It will end up lumpy and bowed. Not a pritty sight.
That is not the real problem now. The real one is the trunion. What do you mean, you heated it up to remove the barrel? If you got it anywhere near red hot, you've destroyed the heat treat of the trunion. It will splay open at the locking lugs when you fire it. I don't know if you know about heat treatment, but you have created a situation where you might have a failure in the locking lugs. That translates to your face meeting Mr. Bolt at 100 miles per hour. Slow down here. You guys have to stop trying so hard and re-think what you are doing. A mechanical press would have been the first thing to do, not heat the trunion to get out the barrel...
We here, will be glad to critique your plans. Please bring 'em here and let some people with experience give you some tips. My first tip is get another trunion to replace the one you heated. Check your barrel too, if you beat it out with a drift it may have crushed the chamber mouth.
Link Posted: 5/25/2003 6:46:22 PM EST
[Last Edit: 5/25/2003 6:55:13 PM EST by mg34ss]
Listen up, time for Heat Treat in your shop entry-101. Steel is a crystalline structure. The crystals are changed in size when you heat and cool the metal. Slow cooling, (big crystals) equals soft metal. Fast cooling, (little crystals) means hard metal. You have to heat the metal to about 1850'F to make the crystals all loose and runny, ready for the quenching process. You cannot do this with a rosebud torch tip. You have to use some kind of furnace or kiln. The metal has to be a bright orange. The whole thing, not just in places. If you put the sheet metal into the kiln when it's cold, and let it heat up slowly, you will experience the wonder of oxide scale. Basically your shiny receiver will turn into a piece of weld slag. The kiln must be hot and the receiver must be placed in it for no longer than 5 minutes max.
When you take it out of the kiln and walk across the shop to place it in a water quench, you lost it. The metal will cool below that little crystal stage and go into the big crystal stage before you take two steps. The thin sheet metal isn't "massy" enough to hold it's heat. You have 1 1/2 seconds max, to get it into the water before it turns out dead soft. You will know if you did it right if it has a nice "ting" when you tap it. If it goes "clunk", you loose. The up side is you can try again. You can do the process over, several times in fact. Metal is not damaged by the heat treat cycle.
The trunion could be salvaged by the same process, but it must be tempered. Tempering involves re-heating the metal to a medium temperature for some period of time, called a "soak" and the slowly cooled to room temp. This take away the over hard brittleness and makes the metal tough. Problem is, who knows how long and how much? Each alloy has exact reheat and soak formulas. These are based also on the thickness and mass of the metal part. We don't know exactly what it's made of or the time required. So you're kind of lost here.
I have made receivers from scratch, so you're getting the facts here. 4130, the sheet metal alloy, is more resistant to hardening than 4140. 4140 may "over harden" and need a soak at around 800'f for 10 minutes or so. This temp level can be checked with a heat crayon available at a welding supply shop. The wax will melt and run when it reaches the temperature you want.
Two presses are just about required to build AK's. A drill press and a hydraulic press. Both are useful for many things besides AK's. Both are worth investing in.
Link Posted: 5/25/2003 8:14:39 PM EST
Thanks for the tutorial MG, after finishing my receiver is it necessary to harden it?
I do have access to a heat treat oven ( 2200 F.max) . Should the receiver be put into a jig because of possible warpage or with your experience do they do OK without a fixture? ( the fixture might keep the temp up until the quench).
Link Posted: 5/26/2003 1:02:02 PM EST
[Last Edit: 5/26/2003 1:10:07 PM EST by mg34ss]
Here's a good tip. I haven't worked with the FAC flat, but I have worked with the bent and flat 4130 available. (I'm a big fan of the prebent blank on the link page.) First thing to do with it is to toss it in the kiln and heat it, then let it cool slowly. It softens into butter. You can practically bend it with your finger tips. This reduces the force required to bend the upper rails by probably 50%. Shape and form to suit, then reheat and quench.
You didn't mention if you have the FAC flat or flat sheet metal. I would recommend heat and quench on the flat sheet metal or pre-bent blank, I cannot say what to do with the FAC flat. The heat treat process might not be the same. If they actually DO use 4140, a heat treat as I described may over harden the frame. This will result in a frame that would break like glass. 4130 is easier to work with because it won't harden into a brittle condition. 4140 will. If you got flat sheet, you probably have some scrap metal around to test with. Try some tests and you'll get a feel for what you need to do based on the characteristics of the test pieces.
There might be small warpage of the frame, but not enough to require a jig. A jig will actually compromise the heat treat quench. 4130 dosen't like to harden, though it will. Most quenches use oil and a slower cooling rate than 4130. To harden 4130, the quench must be violent. Bright orange into cold water instantly. A jig will retain heat and might slow the quench, leaving you with a soft receiver.
Link Posted: 6/6/2003 10:59:34 PM EST
[Last Edit: 6/6/2003 11:14:13 PM EST by OSI]
The issue on the Hesse/FAC/Tannery flats has always been whether or not you mangle the magwell when bending it. We went through several prototype jigs and mangled a few of the flats before coming up with this.

You can read more about it here


I'll be honest, I had my misgivings about heating the trunion also, but the guy who did it is yet to experience a faliure. We will probably end up testing it by running the hottest ammo we can find through the thing. I think he told me that he did not get it quite red hot, but definitely pretty warm.

As for hammering the upper lips. I want to come up with a better way of doing it, and comparing one of our recievers to a stripped Hesse that I bought recently, I can tell that Hesse was doing it with some sort of multi-stage process. Still, the hammer bent rails have yet to fail, not even on the gun that had a milled reciever stub welded to a cut-off sheetmetal receiver.

The big thing is that we have the issue with the magwell deformation 100% licked. Other people seem to have come up with usable designs for barrel presses. In reality, I get the impression that a complete AK making tool kit is going to run someone in the range of $800 to $1000, but the idea of being able to produce the guns at competitive cost to a Romanian SAR in a home shop is intriguing. Also, the tooling does not seem to have any wearout issues that arise with the various AR tooling.

Just like with the old Soviet plans for the AKM, making them in small numbers on costly tooling does not make sense, but in economy of scale, it makes sense if you get a few people together and pitch in to make ten rifles. My guess is about four guys in a reasonably well equipped shop with the AK tooling, a pile of flats, and a pile of parts kits would be able to turn out a bunch of rifles in a weekend.
Link Posted: 6/7/2003 2:55:54 AM EST
[Last Edit: 6/7/2003 3:03:06 AM EST by mg34ss]
Oh my. Why anyone would go through this much work so they didn't have to lay out 17 holes and dremmel out a mag well and a trigger hole, is beyond me. Nice work on the jigs. They are impressive. Your cost analasis is off a bit. I'd suggest, $100 for a cheap press, $45 for a dremel, and, if you like, about $75 for a table top drill press. $20 for a dial caliper. Done for $240. All the tools are usable for other projects. All the home made dies are special purpose and have no other function.
The advantage of a pre-bent blank, you don't have to re-work the trunion for the AK-74, just drill the holes in the correct spot. Now you've skipped the welding step for the rear trunion. This step and the die construction make this process beyond the skills of non-welders. You probably have to have a shop metal saw and a milling machine to do the die work. Also beyond the average guy.
With the pre-bent blank, no heat treat is required, unless you want to. All my scrap and all your scrap was produced getting the bends correct, and you still don't have your top rail bends sorted out. Pre-bent blanks have that step completed. The amount of time you and I spent building dies to do these bends was huge. For anyone planning to build less than 20 guns, it simply isn't worth it. The amount of time saved on the hole layout is lost several fold in die construction and the cost of distroyed flats. This is NOT the way to go if you want to build two or three AK's. It's great fun if you are really into building tooling. That's not a bad thing. If you are building 400 AK's, yeah, do it this way. For the average guy, it's a total waste of time and money... Of course spending the extra $35 over the bent blank price, gets you a finished receiver. I built three AK's with home made receivers. I wouldn't do it again... Well, maybe one more....
Link Posted: 6/7/2003 6:32:01 AM EST

Originally Posted By mg34ss:
Oh my. Why anyone would go through this much work so they didn't have to lay out 17 holes and dremmel out a mag well and a trigger hole, is beyond me. Nice work on the jigs. They are impressive.

That, of course is the real question.

Now, I think the jig is a good idea, especailly if you want to make your own pre-bent blanks. that's where I see its utility. You can choose any alloy you wish and heat treat it accordingly. Once you have your pre-bent blank, you can download the AK receiver template from WECSOG-Blueprints, print it 1:1, bond it on with contact cement, and whip out the old Dremel. Then just rivet or tack-weld the loawer rails in, and you are done.

The savings would come in buying $10 worth of sheet metal rather than a $40-$50 flat.
Link Posted: 6/7/2003 3:45:09 PM EST
On the up side, I really have to admire your skill building these dies. You will be the first flat builder I have ever seen build a successful receiver. Not saying it hasn't been done, I've just never seen one before.
Link Posted: 6/9/2003 5:40:08 PM EST

O. K.
I am reading about the upper lid but how about the rails?
They nearly drove me crazy cutting them and putting them into a sergeant freedoms bent. I still don't have them right.
fac's flat doesn't have them.
Link Posted: 6/10/2003 2:09:54 PM EST
Nice piece of tooling Osi. MG34ss, just out of curiosity in your opinion can Osi bend a customers flat or would he be considered manufacturing?
Link Posted: 6/11/2003 1:27:06 PM EST
Now that's an interesting question. There is some debate on this one. I have my own oppinion, but it is meaningless from a legal perspective. I suspect it would be manufacturing only if you bought several flats, bent them and then sold them. There is no question that that would be considered manf. However, if you bent a flat for a friend, or even a customer, who had a receipt for the flat, then you would be performing a service. This is a grey area. One that would not be something the ATF would even be interested in. Fifty bent flats however, even if your friend had receipts for them, would probably be a problem.
However, in the big picture, it probably dosen't make a diffrence. ATF is interested in big ticket guys, not you. They can't make any money or further their evil reputation by busting you. Probably. So I wouldn't sweat it.
As for rails, buy a set and use them as a guide for making as many as you want. I recomend leaving off the auto-sear slot.
Link Posted: 6/12/2003 9:43:20 PM EST
If we can come up with a quick and easy jig for bending the upper lips correctly, the game would be to put it all on a rolling cabinet that I can haul to gun shows and other gatherings and people could bend their own flats in five minutes for a small fee. Ie a deal where they can buy the flats, bend them if they want to, and then do the riveting and welding at home. It might be possible to set up a portable air compressor with a riveting gun, but the people at the shows would probably bitch about the noise. I figured out that I can fit everything in a rolling cabinet that I had originally built for some other machines. It would work well at some sort of outdoor gun show, but I don't know of any.

The thing is those flats really ought to not cost any more than about $25 each and at that price there should still be plenty of profit margin for the manufacturer. Heck, the going price for a complete and blue Hesse AK reciever at the Portland Expo show is typically $50 straight money, $49.95 for a flat is bullshit, but then even the 80% AR lowers typically cost more than a factory lower.

I am willing to bet that a deal could be made with the Romanians for unfinished flats at a reasonable price. The thing about the Hesse Recieves and flats is that the magwell is somewhat generic to work with several different mag variations depending on what caliber you make the gun. Same deal with their rails, they make the extractor extra long in case it will be used with a 5.45 gun.

I built one gun using a bent-metal reciever but I paid a ripoff premium for the vendor to include a template on it and a set of rails. The thing about those vs a flat is that the bent-metal recievers do not have the indentations in the magwell or the X marks around the holes.
Link Posted: 6/13/2003 2:38:32 AM EST
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