I had s rock river arms upper for a while now.  I wanted to get the good colt mags for it.  So I did.  $300 latter I have colt mags.  With two of the mags I am having trouble with the gun it is faling to eject them.  It is not stove piping it seems as thought the ejector is not hiting them.  the bolt cycles but the case dose not leave the gun it just jams it self into the barrel.  I am not sure but it is only happening with two of the three mags.  I used two diffrent types of ammo.  Winchester Value pack, and fediral classic 115gr +p+.  One mag works thought.  It seems to happen at around the end of the mag 10 rounds or less.  I am thinking this could be a spring issue.  Like it is pushing the live round up to quick or too slow.  I am not sure i don't think it is an ejector problem in that is works most of the time.  any ideas?
Gary