At the BuildFest we had at _Disconnector_'s house a little while back, we usedcosmonaut said:Is there any particular type of oil that should be used?
Steel core is right. It also causes much higher stresses in the steel due to the speed of cooling and you will get stress cracking. There are steels(1040- 1050) that need to be water quenched but this is not one of them. In fact you should probably heat your oil to at least room temperature if it has been outside or out in the garage in the winter. And one way to keep flame ups to a minimum is to submerge the whole piece so nothing is out in the air like a wick.Steelcore1964 said:water can cool it too fast and make the 4130 brittle, harder is not always better, motor oil will not make the metal too hard/brittle due to slower cooling.
I had the holes on my first build (AMD-63) begin to eggshape and I didn't even fire it. Just the consant working of the hammer and trigger started the process (didn't heat treat the holes). I didn't measure the holes to start with and didn't measure them afterwards but I knew that the axis pins were snug in the begining. I then tried the heat an quench (in both oil and water) and I continued to see the holes open up. I then used Kasenit, heating the holes to red pouring the Kasenit on the holes (had a steel backup plate) and then reheated the holes to red again. I then quenched the receiver in clean water (as per directions). From that time on the holes have stayed the same. I don't know how brittle the receiver is around the holes but I do know that holes arn't egging anymore.hcpookie said:We have yet to see/hear any reports of an untreated receiver w/ egg-shaped holes. Would be nice (and expensive) to measure the holes, load up a few cases at the range, and then measure again. That would give us a baseline on how long the holes would be expected to last w/o heat treating.