[foghorn leghorn]

call 1-800-578-3767 ask for replacement mags, or you can attempt to recurve the lipps on the mags to raise the forward part of the lip which will allow the nose of the round to clear the edge of the magazine. Their are two tabs which could use filing, which have no use except to hold in the follower. They get caught on the case when the lips haven't been recurved. Don't put too much torque on the lips, they can break off. Brownell's has a tool specific to ar-15s for this purpose, but I think you can do it with some long needle nose pliers.
p-mag has a great mag on midways site for 18 dollars. Just buy three mags and leave the ones that came with the rifle alone.
this issue has been common knowledge for a while, but what do I know.