Building order from a flat

[MUDSUX]

Hello everyone,

I have been pouring over all the info here and the build tutorial cd but I can't seem to get the sequence in my head. I've read a lot about assembly but hardly anything about working from a flat. I am starting from a flat with a demilled Romy G parts kit with original barrel. Can someone verify or correct me? Thanks in advance:

1. bend flat
2. drill and ream the trigger and hammer hole, then heat treat the holes
3. rivet in trigger guard with stop plate
4. rivet front trunnion in place
5. fit barrel
6. head space barrel

This is where I get confused. Do I heat treat the rails before spot welding or spot weld in, drill center support while the rail metal is still soft, then heat treat. Do I heat treat only the ejector? I read somewhere where both rails were completely heat treated.

7. Rivet center support
8. rivet rear trunnion
9. fit magazine, file rails as necessary

I am sure I am missing something. Any help is greatly appreciated. Thanks

[nalioth]

If it's a G kit with an original barrel, you will most likely not need to headspace it.

Check headspace? sure.

[HillBilly2]

If you rivet the trigger guard before you fit the mags and they don't go high enough then your gonna have to remove it to thin the stop. Use screws to attach it until you verify proper mag fit, then rivet.

[ronin]

Whose flat are you using? With AK-Builder, you can pretty much install the trigger guard and line up the front trunnion with the front of the flat and rivet it in place. Others, you need to do the TG and then test fit the front trunnion until you get a good lock up with a variety of magazines, then you mark, drill and rivet it.

Here's a ballpark (meaning it can vary) order that I follow with AK-Builder flats:

1. Very lightly grease the flat on both sides. Do not go heavy or you will make a mess possibly even deforming things.
2. Bend flat carefully
3. With the flat in the die, inspect lower FCG holes and tap flat with a hammer if need be.
4. Inspect the bottom of the flat and make sure it is flat. Tap flat with hammer and length of metal bar
5. Remove the flat from the die.
6. Install trigger guard and stop plate - make sure the stop plate is positioned right with the tab to stop the select lever on the operating side (I did it backwards once).
7. Install the front trunnion (see my opening note about fitting the magazine if not an AK-Builder flat)
8. Install the lower rails (I fully heat treat them outside of the receiver and am very careful installing them. I have messed up the heat treat on the ejector tip 2-3x by allowing the spot welder tongs to get against the tip when heating. You can correct this by spot heat treating just the tip, but I am careful and avoid it now. When installing the rails, do practice welds first and get used to your welder. You want solid penetration and want at least 5-6 welds per side. Too light and they will not hold up. Note, I use drill bits to align the lower rails parallel to the upper rails and with the "shelf" or opening of the front trunnion - they must be parallel and they must line up with the trunnion to work right. I used to butt the lower rails against the front trunnion and never hard a failure but now leave a very small gap (maybe a 1/2 mm or so max) to reduce the chances of the front trunnion hammering the rails.
9. Install the barrel - I lightly polish the barrel and inside of the trunnion making sure there aren't any burrs. I freeze the barrel for an hour or two and warm the front trunnion with a heat gun. I literally pull the barrel out of the freezer and run back to the shop, apply some anti-seize compound, line up the barrel by sighting between the "ears" of the front trunnion to try and line up the the RSB with it. Note, inspect the barrel and its components to make sure they are all in one dimension and not canted. I then push the barrel in by hand part way and give it some taps with a mallet on an old brake I cut flat. The brake protects the muzzle from getting hurt. I sight down the ears to the RSB again to make sure everything is square and then press in the barrel slowly and carefully. Use a qtip or whatever to clear out the barrel pin hole so you can see when the barrel pin channel lines up.
10. Make sure the chamber is clean before you headspace.
11. Now, at this point, I headspace before I install the barrel pin. You need to strip the bolt - especially with Yugos - to make sure the extractor isn't hitting the barrel and interfering with the headspace measurement. The bolt should be able to close on go and not on no-go. I use Manson gauges and they have worked just fine for me.
12. Assuming it headspaces okay, I then install the pin and check headspace one last time. If it does not headspace okay, you need to move the barrel in or out and the drill the hole out for an oversize pin, a procedure that I will not detail right now.
13. Install the rear trunnion - I do this after so I have more working room.
14. Install the center support I do this last so I can wiggle the rear trunnion around easier.
15. I then test fit the bolt carrier by itself and run it back and forth looking for any fine tuning I need to do to the rails. Have the gas tube installed when you are doing this to make sure the geometry matches.
16. Now, install the bolt. It will hit the ejector because it is too long. One every rifle, I hand file (no power tools) the ejector such that when the bolt goes by, even if the carrier is pushed as far to the opposite side of the receiver as it will go, the ejector will still pass through the bolt face, hit the case and eject the spent round. If the ejector is trimmed too short, it will either fail to eject or intermittently/randomly fail to eject depending on the position of the bolt and case relative to the too short ejector. You want to go slow, remove a little and test over and over. It is a bear to rebuild one hat is too short. It can be done but it is very tedious. With a power tool you risk going too fast and taking off too much not to mention ruining the heat treat (as mentioned, I heat treat the entire lower rails before I install them).
17. Test fit a variety of magazines. Don't be surprised it you need to sand down the back of the magwell area slightly. Any adjustments should be fairly minor. You should not need to sand/shape the front trunnion. With AK-Builder rails, you will want to grind the stabilizer tabs down so they help position the magazines and snugly hold them in space. I do the rough shaping with a die grinder and carbide burr. Be careful as a tool like that takes off a ton of material fast. Until you have experience, the key is to take off material and test over and over. Grinding them too short is not the end of the world - you just loose the benefit of a nice snug magazine consistently lining up the cartridges for feeding. Regardless, why rush? Just take your time until all your magazines fit nice.
18. Drill out all the holes and ream them to size
19. Test fit FCG axis pins to make sure everything is cool
20. Heat treat the holes. Note, I only use oil now - in my case used engine oil that I store in an old 12-14" cannon fuse container epoxied to a board so I can dunk the receiver in. I have stopped using water as I have cracked a few FCG holes before I learned that the water must be relatively warm because relatively cold tap water can cause the steel to shrink too fast. Basically, I heat the holes to a yellow-orange color by eye in the shade so I can see their color. I then dunk the receiver into the oil. This is messy but it works for me. I only do the 4 axis pin holes. Clean the holes off until the steel is shiny silver again. Now, heat each hole until the steel turns blue and let it air cool.
21. I polish the back of the hammer so it is glass smooth using very fine sandpaper and a Dremel (not the drum but the little flat sandpaper discs).
22. From here, I install the FCG. Make sure the disconnector spring is installed and make sure the hammer is facing the right direction.
23. Be sure to function test for safety. Pull the bolt back - the hammer should be held. Pull the trigger and it should be released. Next, hold the trigger back and cycle the weapon. The hammer should again be held and not follow the carrier back. Pull the trigger and it should release. If the trigger hooks or the disconnector fail to grab the hammer and it follows the carrier back into battery, then something is wrong about either the installation of the hammer backwards, no spring in the disconnector, something bent wrong, etc. At any rate, the weapon is not safe.
24. I put a light dab of wheel bearing grease on the back of the hammer, and other FCG parts that make contact, plus on the bolt's shaft, the bolt cam groove in the bolt carrier, and on the rails. I then give it a quick spray of CLP to make everything nice slick.
25. I install the bolt into the carrier and install it into the rifle followed by the spring.
26. I test all the functions again before I seal it up.
27. Also, I run cleaning patches down the bore to get rid of any debris. You'll find that the surplus barrels have a ton of cosmoline and dirt that need to be removed. Cleaning is a safety and accuracy issue.

The above isn't etched in stone. I don't always follow it exactly but it does give you the ballpark idea of order and method. The most important thing is to take your time and do it safely. If things don't seem to be going together right, stop, take your time and think about it or even post here. The one AK front trunnion that I ruined, I was tired and started fiddling with rather than stop and realize I had made a mistake with the riveting at the start.

Hope this helps.

BTW guys, correct anything I messed up/overlooked. I wrote it on the fly so I may have forgotten or mixed up something.

[MUDSUX]

Thanks Ronin!

Everything I have is from AK-Builder except for the trigger guard rivet drill guide/barrel press ram & plate/front trunnion barrel reinstall press fixture which I got off gunbroker from GulfBeachBum as a package.

This is great and I will most likely follow this order for my build. It's like I have too much info from everywhere and it's hard to know what is right and what is wrong.

I have one of AK-Builder's new flat bending jig and when I bend the flat, the bottom is not completely flat. I looked and it seems the bottom plate for the punch is not completely flat. I don't know why it is like that.

Do you find that it is hard to trim the bottom rails after heat treating? I read somewhere to partially trim them outside of the receiver, before heat treating and installing.

[ronin]

I haven't had any problems trimming the lower rails after the heat treat. The only things you need to trim on an AK-Builder lower rails are the ejector tip and mag guides. As mentoned, I use a file on the ejector tip and a die grinder with a carbidge bur to knock down the mag stabilizers. I do the finishing work on the mag stabilizers with a stone in a Dremel. You could use a sanding drum, stone or whatever for all the shaping work on the stabilizers - I have carpal tunnel and using a file for a long time is a real bear as a fair amount of material needs to come off.

On the guides, I do taper them slightly - wide at the front and narrower to the rear. The idea is that the magazine can be inserted fairly easily become increasingly stabilized as it is seat and locked into place at the rear.

[ronin]

BTW, I haven't used Curtis' new jig but it seems to me it should bend completely flat - his old one does (I have one of his original models). The bottom of the receiver must be flat or the magazine catch and FCG geometry will be thrown off.

Is the jig new or used? I wonder if someone pressed the die in too far and bent the frame.

[MUDSUX]

The jig I got new from Curtis. Here is a pic of the bottom bar for the punch. Looks intentional to me, he milled the sides. Not really sure why though but there must be a reason. AK-Builder stuff seems top notch to me.

[ronin]

Edit: I just watched the video on his site and am not sure what to tell you. I'd recommend you call him.

He's a great guy to deal with. He's not too red hot with email but I've had very good luck with calling him. All my AK tooling is from him and he's been very responsive to my questions over the years.

[MUDSUX]

I am pretty sure that's how they are suppose to be. Anyway, thinking about following this for heat treating:

Heat treating

Is there a better way?

[ronin]

Actually, that's the method I follow with the exception that I only quench in used engine oil now - no water.

[MUDSUX]

Awesome. Thank you. Will try it this weekend.

[ronin]

Have fun. Just take your time & let us know how it goes.

[MUDSUX]

Ok so I tried heat treating the rails this weekend with my MAPP torch. I am having trouble getting an even orange color across the length of the rail. Is there a trick to this? As soon as I get one end orange and move to the other I lose the color. I tried moving back and forth, tried shooting parallel down the rail, nothing. Anyone have any advice? Orange is the right color correct? I cannot get it to yellow. Thanks

[ronin]

Crank up the heat/output pressure and go back and forth to heat it up. A lot of guys, maybe even most guys, use a MAPP torch so it does have a proven track record of working.

BTW, I wouldn't worry about absolute uniform perfection. The ejector is the most critical part. At least make sure it is bright orange when you dip/drop it in the oil.

I use an oxy-acetylene (OA) torch and when I am holding the part with pliers, the ejector is the last thing I hit before dropping it in the oil just to make sure it is hot enough.

[MUDSUX]

Thanks Ronin,

My MAPP torch only has one knob and it was at max. Why do you only use oil now?

[KernelKrink]

The critical temp happens when the metal loses it's attraction to a magnet, use a pocket magnet to see if your heated rail sticks or not. Color is subjective and looks different in different room light.

Oil is recommended because water can cool the steel too quickly, causing stresses and cracks. Some steels are rated for a water quench, but the ones commonly used in flats are rated for an oil quench.

[MUDSUX]

Thanks Kernel,

What weight oil do you use?

[ronin]

I literally just use old/used engine oil. Given our vehicles, it will be some combination of 5w30 to 10w30. I keep it in an old 10-12" tall and maybe 4-6" wide fuse can that has a screw on lid. That way, I have a ready made dunk tank whenever I need it.

Before I thought to make the dunk tank out of the fuse shipping tin, I used all kinds of stuff. I even used a plastic container once, dropped the rail and it melted the very top layer of the plastic before it cooled all the way.

[ronin]

BTW, I ruined a receiver with cold water once. It shrank so fast the metal snapped and I had 1-3 cracks radiating away from each of the 4 holes. I've never had that problem with oil and have stuck with it.

There are guys with water blends that have additives to help address the problem. Rather than spend the money, I just stuck with oil and the associated cleanup.

[MUDSUX]

This is very interesting. I am somewhat of an amateur knife builder, have 2 under my belt, and those guys all want to use fast quenching. I always sent my blades out to be heat treated because I don't have to right equipment. I guess it all depends on the type of steel and thickness etc.

[ronin]

Originally Posted by MUDSUX

This is very interesting. I am somewhat of an amateur knife builder, have 2 under my belt, and those guys all want to use fast quenching. I always sent my blades out to be heat treated because I don't have to right equipment. I guess it all depends on the type of steel and thickness etc.

That's what I gather too - alloy especially.

[buffalo]

I use the new ak-builder flat bending jig for my flats also,these are the steps that i do my builds in,this has worked for me.

**Steps used on a matching parts kit build**

Bend the flat
drill trunnion holes
drill and ream fcg holes
dremel off any sharp edges left from drilling
Spot weld in bottom rails after heat treating the RAILS(not the receiver)
Heat treat the receiver(i find i don't get any warping if the rails are already in)I just use a propane torch from homedepot and a bucket of water.
place center support and rivet in place and hold there with duct tape till later
rivet in front trunnion(i place all rivets in thier holes first so there is no shifting)
rivet in trigger guard
rivet in rear trunnion
remove tape from center support rivet and squish
dremel down the bottom rails for proper mag fitment
dremel down any front rivets that might be sticking up just enough to clip barrel
Press in the barrel
dremel down ejector so it clears the bolt(dremel very slowly so you take off just enough,to much and your screwed)

Those are the steps i use,hopefully that helps some.

[MUDSUX]

Thanks Buffalo!

[buffalo]

Originally Posted by MUDSUX

Thanks Buffalo!

Your very welcome,hopefully some of that helps. That is the process that after many screw ups i have found to work the best,i haven't had to start any builds over since i started doing it in that order.

[synweap223]

Originally Posted by MUDSUX

THIS IS MY PROCESS, YOURS MAY BE A BIT DIFFERENT. CAPITALIZED MY REPLYS TO SEE EASILY, AND NO I'M NOT YELLING.

Hello everyone,

I have been pouring over all the info here and the build tutorial cd but I can't seem to get the sequence in my head. I've read a lot about assembly but hardly anything about working from a flat. I am starting from a flat with a demilled Romy G parts kit with original barrel. Can someone verify or correct me? Thanks in advance:

1. bend flat
HEAT TREAT EJECTOR, & WELD IN LOWER RAILS
2. drill and ream the trigger and hammer AND CENTER SUPPORT hole, INSTALL CENTER SUPPORT, then heat treat the TRIGGER & HAMMER holes
3. rivet in trigger guard with stop plate
4. rivet front trunnion in place
9. fit magazine, file rails as necessary
RIVET REAR TRUNNION
FINISH (YOUR CHOICE, BLUE, PARK, ETC)
5. fit barrel
6. head space barrel

This is where I get confused. Do I heat treat the rails before spot welding or spot weld in, drill center support while the rail metal is still soft, then heat treat.( I TYPICALLY HEAT TREAT THE EJECTOR FIRST THEN WELD IN THE RAIL.) Do I heat treat only the ejector?(ALL THATS NEEDED) I read somewhere where both rails were completely heat treated.

7. Rivet center support(DONE)
8. rivet rear trunnion(DONE)
9. fit magazine, file rails as necessary(DONE)

I am sure I am missing something. Any help is greatly appreciated. Thanks

Again, this is how I do it, others may have different approaches.

[Dan FS71]

My sop:
1) Bend Flat
2) Drill Front Trunion Rivet Holes (use adjustable vise @ 90 degrees)
3) Rivet Front Trunion
4) Drill Rear Trunion (some flats are pre-drilled)
5) Rivet Rear Trunion
6) Heat Treat Ejector "Tip" Of Left Rail
7) Clean Rails And Receiver
8) Spot Weld Rails Into Receiver (left 'ejector side' first) - (7 spot welds each side)
9) Drill Center Support Rivet (move hole .030 toward rear trunion and .030 down toward bottom)
10) Drill and Ream FCG Holes
11) Rivet Center Support
12) Heat treat FCG Holes
13) True Up Receiver So Bolt Carrier Runs Smooth (may need to slightly sand the top rail to flaten it)
14) Mill Ejector 'Tip' To Correct Size
15) Mill Mag Lower Rails
16) Fit Trigger Guard And Holes
17) Rivet Trigger Guard And Pistol Grip Nut
18) Make Bullet Button (if none are ready)
19) Polish Barrel Chamber And Trunion Area
20) Install Barrel Into Receiver
21) Disassemble Bolt And Check Headspace
22) Install Barrel Pin
23) Install RSB Leaf
24) Fit Receiver Cover And Locking Pin
25) Install Folding Stock And Make It Permanently Fixed
26) Final Fitting
27) Recheck Correct 922r Parts Count (6 on AK's)
28) Done

[MUDSUX]

Hey Dan,

Why are you moving the center support hole? Are AK-Builder's flats not located in the right place?

[Dan FS71]

It's easy to do on a mill & wonky mags will fit without filing.

[resting]

I basicly follow Ronin's build order. I heat treat with a MAPP torch checking the areas with a magnet before quenching in very hot water with a bit of dish soap added. I draw the pieces by heating them in kitchen oven at 550 degrees for one hour. I trim the magazine stablizers close to size on the lower rails before heat treating and spot welding and then only have to do a little filing on them to get a final fit after welding them in. I rivet in the rear trunnion last in case I need to stone or file the upper rail to get the bolt and operating rod to slide smoothly as this gives me a little more room to work.

When I'm building from a barreled kit I always check headspace before pushing out the barrel and then measure the gap between the front of the trunnion and the Rear Sight base with feeler gauges and write down the resulting measurement for later use when pressing back in the barrel.

I finish the barrel and receiver seperately with GUNCOAT, bake the two assemblies and then press the barrel in. This just makes it easier to fit in my oven. Once I have the barrel started well into the trunnion I place a feeler gauge .002 larger between the rsb and the front of the trunnion and GENTLY press the barrel until I get to zero clearance and then release pressure on the press and visually check alignment through barrel pin hole and then check headspace. If good, I push in the barrel pin and check headspce one more time.