No. They weren't "mistakes". They intentionally did not ban arms, because if they did the law would have been thrown out by the courts under the Miller test; "suitable for Militia use". So they made an incremental law that could pass; cosmetic features. Now Heller and McDonald are even tougher for them to get around.
If Congress makes a law that bans AR15's (which they won't) it would be quickly tossed by a federal judge. Fundamental rights cannot be legislated away. They haven't been, are not now, and will not be.
All this chickenlittle panicing plays right into the anti's plan.
Feinstein says "Boo"! I'm not scared of her. I know my rights.
As much as I agree with you on the odds of a bill passing, there are a few points that we ignore at our peril:
1. Don't depend on judges, federal or otherwise to protect your rights...history should prove why. The 2nd Amendment can, has and will be ignored/reinterpreted just as easily as all three branches of government have ignored/reinterpreted the rest of the Constitution and Bill of Rights. We are now a country where one can be spied on, indefinitely detained or even killed by our government without due process of law - do you really think the omnipotent government types give a darn about Amendment #2?
2. If anything passes, it will be the background checks. Even gun owners are piling on that bandwagon. If that doesn't change, expect some kind of background check bill to pass as a quid pro quo for some other legislation...like Medicare cuts, for example. Besides the obvious negative effects on private sales, consider this...based on the wording of some of the bills introduced at the Federal level, it will be illegal for a non-licensed buyer to take possession of a firearm without going through a background check. Think about that for a minute...if you have any firearms that were not purchased from private sellers without some kind of notarized receipt, how are you going to prove that you took possession of that firearm before our hypothetical law went into effect? What is going to prevent them from charging you with illegal possession of a firearm?
Remember, we're talking about lawyers and politicians here...words are their game, they make their living by taking seeming innocuous words and twisting them to their purpose.
I applaud you for not buying into the panic...but keep in mind that knowing your rights isn't enough...you gotta be able to defend them against those who don't give a crud about trampling them.