I am planning an AMD-65 build.  I am considering a Cold Steel Solutions 80% receiver because they already have the dimples in them.  They come either in .064 or .040.  They make the .064 ones either in 4130 or plain sheet metal, and the .040 ones in 4130 only.

Their site states that you need to heat treat the entire receiver if you use the .040 ones.  From what I've read, I know that you can heat-treat around the holes using a torch but you can't treat an entire part.  

I would like to use the .040 receiver because that's what the AK is supposed to have, but is what they're saying correct?  I haven't seen anyone else stating that you need to have an entire receiver hardened.  This is my first build and I'd rather not have to mess with the internals a lot to make them fit a thicker receiver.  If anyone has any experience with this, I'd greatly appreciate your input!

Also, what are your opinons on Ace Arms receivers?

I built 3 using Ace Arms blanks.
They have the best template I've found.

All you need to heat treat is the pin holes and the ejector

Shouldn't you treat the rails too?

Yes......The rails and holes must be treated.
But you should be just fine with that. It would be a good idea to treat it all but unless you have access to a kiln or furnace that can maintain 1200-1500 degrees you really don't have that choice on an untreated receiver.
You can use a "map" or "Propane" tourch to heat each hole and to heat the rails to quinch and temper. But your main concern are the rails/ejector and the receiver pin holes. Do NOT try heating the whole receiver with a torch. You need a constant surface temp. to really do you any good. This method could ruin it by warping the material or breaking down the properties in the steel and make it very brittle/weak.
                                               To quinch:
Heat untill a very bright orange Approx (1200') than plunge into ICE cold water.
This has to be done within a very short period so make it quick, without getting burned. Becarefull!!
                                               
                                               To temper:
Heat back up to a dark blue approx (900') than set aside and let air cool.

By "Quinching" You're damagnetising the metal and strengthining the internal properties of the 4130 carbon.    
By "Tempering", This would be the surface hardining.
Use this same method for each individual hole.
Be sure to practice on scrap stock, before treating your final peice or part.
By repeating these steps to many times could result in a hard but brittle finish.
Use a file to test the strength of the steel.
Thicker receivers: A little more work...But well worth it.
If you decide to go with a thicker receiver such as the .06 instead of the .04 4130, Don't forget you're going to have to trim the front and rear trunion sides with a surface grinder to fit.
That's where the precision comes into play use a digital "vernier" to calibrate the trunions to fit the thicker receiver.
Hope this helps and be carefull!!!,
Shadow                        

Yuo do not have to treat the entire rail, just the ejector.

Ok, I have a technical question on the heat treating.

If I heat treat the rails and pin hole with a MAP torch do I complete the heat treating on each hole before starting on the next hole or can I heat each hole to the Orange stage then quench, go to the next hole and heat it to orange then quench until I have all the holes to that stage, then after all the holes have gone thru the first heat and quench stage can I then heat each of the holes to the blue stage and let the reciever sit and cool??

I'm about to do the same thing. Seams to make sense. I think if when you quench take your time, let the metal cool way down. Then wait till it's kinda cool to the touch. I have not done this myself but am about to.  Maybe somebody with a little info will chime in. Good luck

Victor,
I think you should be ok, as long as you heat each (quench) hole individually the first go around.
The first step is the most critical part. With tempering, it needs a slow cool anyway.......So you should be fine. Don't forget to test your hardness with the edge of a file after cooling, to make sure you have completed the hardening state. You can also use the same method to quench by using automotive motor oil. This provides an extremely reliable moisture barrier. But by heating a peice of steel to  1200' could cause a fire, and be very harmfull. So be carefull!!!  
The method I use is the ice cold effect with salt water, Yes table SALT. The iodine in the salt anneals the carbon in the steel by changing it chemicaly somehow. I'm not really sure technically, but it seems to be a little harder. If you use salt water to quench, this almost immediately causes slight surface rust. But can be buffed out pretty easy. And with a light coat of your favorite protectant you should be just fine.  By the way......don't forget to use warm water to melt the salt before you add the ice. Just use a little common sense, J.K.
All and all, the ice water by itself should suit your needs just fine.            

Hope this helps,
-Shadow-      

Krallstar,
Read my prevoius reply to the post again.
To quench, You have to use a violent dip with the part into the cold water. This means as it is heated "orange/white" plunge very quickly within two seconds or so.
Use a rag to cover your hand just incase. BE CAREFUL!
The second stage "Tempering" the annealing process, is the slow cool effect for the material.
-SHADOW-  

Thanks for the reply Shadow.
So you think that I will be ok by heat/quenching each hole then heating each hole to the second stage and let cool will harden and temper the holes where they need to be right?

Also, you say checking the hardness with a file, can you tell me a little more about how you do this??

Thanks for the info guys.

Good, I'm glad I can do this myself without paying to put this thing in an oven.

What's better for heat-treating... acetylene or MAPP?  I have access to acetylene if I drive to a garage, but I know it can go from zero to spatter very quickly.  Is MAPP safer to use on a receiver?

To heat the receiver you can use either (Mapp/Acetaline) or propane.
But with acetaline, It heats up extremely quick so becarefull not to damage the receiver by getting it to hot. You can warp it this way.
Pay attention to the color of the metal while heating,  that's were your heat factor plays a part in somewhat indicating on the temperature of the material.
Turn to a medium-low heat for Ace./mapp. For (Propane) heat to a high-medium.
It may take a little longer, but you can pay attention to the color of the heated metal a lot better.
Hope this helps,
-Shadow-        

Victor,
Buy using the file take a peice of untreated stock scrap, and use the edge of the file to bite into it cutting the metal.
Now use the same method on a peice of stock scrap (Quenched).
You'll see what I'm talking about.

Quoted: This provides an extremely reliable moisture barrier. But by heating a peice of steel to  1200' could cause a fire, and be very harmfull. So be carefull!!!   The method I use is the ice cold effect with salt water, Yes table SALT. The iodine in the salt anneals the carbon in the steel by changing it chemicaly somehow. I'm not really sure technically, but it seems to be a little harder. snip All and all, the ice water by itself should suit your needs just fine.             -Shadow-

I had asked if it would be acceptable to quench in water in this thread www.gunsnet.net/forums/showthread.php?p=1853836#post1853836 and I was advised that water would make the metal cool to fast resulting in a brittle state...  

I am a newbee at this but can someone in the know try to discuss the pros/cons of oil vs water...?

Yes......Water, Then heat back up to a dark purple/blue then let air cool. Anealling.