I need some help I have a romy underfolder that I built.  I noticed some peening on the ejector after only 50rnds.  This is the first ak builder flat that I have used.  I have built several tapco flat guns and the heat treating worked and have no peening. 

I need some suggestions on how to correct this.  Can I just heat treat it again or is there something else I have to do it correctly?

That part was probably not heat treated would be my guess. I would think a simple case hardening followed with a temper would do it.

start at doing the heat treatment all over again..... you have a 90% chance that this will correct the issue. is it possible that the ejector missed the tempering part of the heat treatment?

But if this still seems to be an issue, ask him if any heat treatment problems have been reported, and what he advised to correct it. (could have been a bad batch)

I have used his older ones and had no problem, and have worked with him many times in the past, and he typically had the correct dies, steel, dimensions etc (better then the others). but I don't know if he changed anything since then.

I will try it again.  I will bring the temp up and see what happens.

If it were me, i would case harden it. I have donethis a few times with sucess but i am not sure how hard the parts are. What i do is heat the part to a purple orange color, not red hot, just before that point, then dip it in used or new motor oil. That adds carbon to the steel. I did that 2 times to the rear of a firing pin.

Once you do that the part is HARD, but, it is also in a brittle state. So you have to temper it.

To temper it you simply heat it again, and dip it in water.

Worked for me.

I am not totaly sure if that is a very high tech or correct method but it does work.

A simple way to harden if you are not good at judging  temp / color.

Heat part till it ceases to be magnetic (requires magnet) then quench.

You can also temper in your home oven at 350 for about 20 to 30 min.
Don't go longer or you will take out the hardness.
Good luck
If you run into a problem with the ejector let me know i recently came up with an idea for replacing the ejector without building a new rec.
Its in the testing phase but 500 rounds into it and its holding and working so far.
Ryche

Tried again.  Doesn't seem to have worked.  Hit it will file still seams soft.  Going to put some rounds through it and see what happens.

Did it work? If not, try the case hardening techinique i described.

Hey I've got a friend that tried this says it worked for him.
I haven't tried it yet but we came up with the idea in a kick ideas session.
Use a spot welder to heat up just the ejector, especially the front edge
when it hits yellow red then drop in oil sitting right below it, so it doesn't have time to cool down. Then use a torch to warm up just a little for
temper. Nothing past light blue or you will make it too soft. Just warm it up a little and let it air cool. He tried it on a piece just completed and seems to be doing fine no peaning after 100 rnds.
With a spot welder it only takes a couple of seconds so watch carefully.
Also the hard part is balancing the welder right over your oil. He used an old hub cap filled with enough oil to cover the ejector when put in it.
If you try it good luck I will be trying it myself as soon as i get back in the shop.
Ryche   P.S. let me know if it works for you so we can let everyone know.

If it has not worked by now time to admit the piece of steel was probably low grade get a better piece 4140 grade remake the part