Yep, assuming you buy a can in stock, you submit your Form 4 stamp and $200 dollar check immediately. Your check is cashed, usually within a few weeks. Your Form 4 sits at the ATF until your examiner works through all the forms assigned to them that were submitted before yours, then they start on yours, submit you to the FBI for a basic background check, then if you're immediately cleared, process your form in a few days. The vast majority of the wait time passes as you are waiting for the examiner to process all the forms ahead of you, thus, every time you submit a form, you have to wait for the folks ahead of you at that time to get processed first. There's nothing special or particularly time consuming going on, the ATF is not funded and manned to the levels required to process all the forms submitted in a reasonable time, so you wait until they work down to where your form is in the stack... every time you submit a new form. Congressional mismanagement at work.
~ One exception that seems to be in effect now is that if you submit a bunch of forms, even if they are over a few months, you may wind up having all of them processed at the same time on the same background check. It's not just 2-3 forms that will trigger batch processing though, the magic number of forms appears to be ~9 or more.
