Just finished my first build. I wanted to see if it would chamber and eject correctly. The first one chambered and ejected fine. The second one chambered but when i went to eject it, it never ejected and the bolt pushed the third up. The round is now wedge under the chambered round. Can't release the mag.

Separate upper from lower and go from there

Put down your purse, push mag. release button and rip the magazine out.  Let the bolt slam home on the chambered round and then pull back charging handle with authority.
 

Grip and rip the mag.  The rounds in the mag will shift enough that the round which is hung up will be freed from the assembly.  Then lock the bolt back, clear the jamed and unfired round.  Let the bolt go forward and cycle the bolt until the stuck case comes out.

Take a good look at the stuck case and make sure you don't have a worn chamber by looking for any gas burns on the case.

If you can't get the stuck case out with the bolt, lock the bolt back and very carefully, paying close attention to not damage the muzzle, use a cleaning rod from the muzzle end to kock the case free from the chamber.

Examine your bolt extractor and make sure it's clean and ensure that the extractor tooth isn't broken off.

If you are worried your going to damage your mag, taken another mag and load some rounds in it.  Put another round across the gap between the feedlips and push down...it should load into the mag.  Congrats, you just saw that the rounds will move as you rip the mag and you just learned how to properly load the mags instead of trying to slide rounds in front to back.(we've all been there).

Wes

LMAO

Lock bolt to rear
Remove mag
Sweep chamber with fingers
Cycle action
Insert fresh mag
Cycle action
Fire (if needed)

OK, that worked. I tried to chamber it again and it worked fine. Next question... Is it safe to shoot the couple of rounds that I loaded and unloaded or not? They have seemed to get quite a few scratches from doing this and the rim of them are not as smooth anymore. How about the one that was wedged? It has a few dents in the bullet head. Is that safe to shoot or no?

The scratches won't matter but if there is any bullet setback then pressures can become very high.

 

So the best thing to do is not to use the wedged one since it may have pushed the bullet back when trying to chamber? Can I pick my purse back up now, Aardvark? gees

just measure if they are the same overall length.

Should I check the head space for this gun? The BCG is from PSA and the barrel is DPMS.

If you put the barrel on the upper, yes.