I wouldn't call it replaced. I think there needs to be a five day rule still. More of a "cooling off" period in case someone decides to buy a gun and go shooting in a school.
The five-day waiting period for handgun purchases expired on November 30, 1998 and was replaced by a computerized criminal background check prior to any firearm purchase from a dealer holding a Federal Firearms License (FFL). All dealers, manufacturers and importers must verify the identity of a non-FFL customer and receive authorization from the National Instant Check System (NICS) which often takes only minutes instead of the several-day waiting period.
Unless an exception applies or the purchase is being made using an approved alternative method, Brady Law requires that background checks for individuals be conducted before a firearm may be purchased from a dealer, manufacturer or importer. Unless there are additional state restrictions, the firearm may be taken upon NICS approval. Purchases from a non-FFL seller are not subject to the Brady Law, but may be covered under other federal, state, and local restrictions. This distinction prevails without regard to the locus of the sale. Thus FFL sales at gun shows are still subject to NICS approval while private sales are not. The so-called "Gun Show Loophole" would be more accurately called a "Private Sale Loophole."
The Brady Law does not apply to licensed Curios & Relics (C&R) collectors, but only in respect to C&R firearms. The FFL Category 03 Curio & Relic license costs $30 and is valid for 3 years. Licensed C&R collectors may also purchase C&R firearms from private individuals or from federal firearms dealers, whether in their home state or in another state, and ship C&R firearms in interstate commerce by common carrier. Curios or relics are defined in 27 CFR 478.11 as "Firearms which are of special interest to collectors by reason of some quality other than is associated with firearms intended for sporting use or as offensive or defensive weapons." The regulation further states
To be recognized as curios or relics, firearms must fall within one of the following categories:
(a) Firearms which were manufactured at least 50 years prior to the current date, but not including replicas thereof;
(b) Firearms which are certified by the curator of a municipal, State, or Federal museum which exhibits firearms to be curios or relics of museum interest; or
(c) Any other firearms which derive a substantial part of their monetary value from the fact that they are novel, rare, bizarre, or because of their association with some historical figure, period, or event. Proof of qualification of a particular firearm under this category may be established by evidence of present value and evidence that like firearms are not available except as collector's items, or that the value of like firearms available in ordinary commercial channels is substantially less.
Obtained via Wikipedia.
~Brian