The problem is when you do a NICS check for the first time, they have no info in the database on you, so they have to check more sources for the first time. This is why they delay your sale. Once you are approved the first time, future sales refer them to the prior approval and it becomes faster.
Personally, I am not ever going to buy any ammo in NY, because they are using the info to set up an unconstitutional registration data base of everyone that ever buys ammo in NY. They may already have an unconstitutional registration data base on everyone who ever did a NICS check for a gun in NY, but that is illegal by law and they don't know about guns that were transferred in the past without any FFL involved or a NICS check being done. They want everyone on their radar. That can only be for one reason. Future confiscation.