To answer your quetion, let's assume that you are not using the Shopping Cart Trick, nor are you applying for multiple cards from the same issuer at the same moment (e.g. three Citi cards, in which you could ask Citi to do one hard pull for all three).
Let's also assume that you already had a very low CC utilization, so improving your total credit limit from the new cards won't help your score.
Finally let's assume that each application is approved.
There are several scoring factors that will be affected by the apps, any or all of which could give you a penalty:
* The hard inquiry (which will usually be performed on only one bureau and therefore could penalize only scores from that bureau)
* The drop to your AAoA (Average Age of Accounts)
* The drop to your AoYA (Age of Youngest Account)
* The increased percentage of your accounts that are considered new (for this discussion we'll assume that the model defines an account as new if it is less than 12 months old)
Different people will experience different impact depending on what their profile looks like. If a person has many inquries already at Equifax, then one more at EQ will likely result in no penalty at all. If a person has several accounts (cards, loans, etc.) already, then the impact to his AAoA will be very small compared to a person who had exactly one very old account.
The most notable issue here is AoYA. If a person has an AoYA of greater than 12 months, then the first new card in the spree will result in his AoYA going to zero months (once the new account appears on the report). That could have a big effect. But subsequent new cards in the next 60 days will simply cauuse the AoYA to stay very low, which will not lower the score further. Once the spree has ended, then the AoYA wil start going back up; as it does that, and certainly after it crosses 12 months, you will see a substantial improvement.
Bear in mind that lenders and CC issuers have their own internal metrics that they use in addition to the FICO score. Thus your FICO score changing is only one issue to consider. Some issuers might see that you opened "too many" cards in the last 30 days, or 90 days, or 24 months, or whatever their own rules are -- and even if your score is over 800 you might be denied on that basis.
