News items today indicate that the Senate gun bill will not contain Feinstein's bans on assault style weapons and on magazines over 10 rounds. However, Reid promised that each of those bans would be introduced to the full Senate as separate amendments to the bill, thus they will each get an up or down vote of the full Senate.
The bans were dropped from the bill simply because the bill would not pass with them. I think the political purpose of allowing the full Senate to vote on the bans by allowing the ban amendments is to allow those democrats from states where the bans are popular to "show their stuff" by voting for the bans, while those democrats from states where the bans are unpopular can show their voters that they oppose the bans, yet still support the main bill.
2nd Amendment bills are a "hot potato"; wait and see if Reid even goes near any of this or even says anything positive about a ban; if he does he can start counting the days until his membership in the "good ole boys club" is history by way of the gun owners of Nevada.
The Democrats dropped it from their bill for lack of support. I think one of the issues is that the Dems from pro-gun Red States didn't want to go on record as having voted for it, or against it, for that matter. Voting on them individually would be an exercise in futility.