The chief lobbyist for the National Rifle Association has been fired in the wake of a falling-out with the Reagan administration over a proposal to abolish the Treasury Department's Bureau of Alcohol, Tobacco and Firearms, according to sources close to the gun lobby.

Neal Knox, director of the NRA's Institute for Legislative Action, and James Norell, his executive assistant, were removed by NRA chief executive officer Harlan B. Carter, the sources said yesterday.

Officials of the NRA, which boasts 2 million members nationwide and is considered one of the most potent lobbying groups in Washington, refused all comment yesterday on staff changes.

The reported shakeup comes a month after the group reversed its longstanding position on the fate of the BATF and, in the process, incurred the wrath of White House counselor Edwin Meese III, according to congressional sources.

For years the NRA had lobbied to eliminate the bureau, which enforces federal gun laws. It appeared to have scored a major victory last year when the administration announced it was was doing just that.

But when the NRA discovered that the administration's reorganization plan called for the gun-law enforcement responsiblities to be shifted to the Secret Service, it did a flip-flop.

It reasoned that the service might be a more vigorous enforcer and, given its positive public image, less vulnerable to political attack.

The NRA supported an alternative measure that would keep the BATF alive but severely curtail its funding and enforcement capabilities. A Senate Appropriations subcommittee approved that approach last month, reportedly over the strenuous objections of Meese, who was the administration's chief lobbyist on the bill and who expressed his displeasure with the NRA's switch. The bill is in limbo while the "It's been a bad stretch for them, but I'm surprised. Neal Knox is a very effective lobbyist and political operative." administration tries to work out a compromise.

One source speculated that the firing was related not only to the BATF flap but to other recent NRA setbacks.

The NRA's chief legislative priority this year has been passage of a bill sponsored by Sen. James A. McClure (R-Idaho) and Rep. Harold L. Volkmer (D-Mo.) that would weaken the record-keeping requirements of the 1968 handgun control bill.

Though the bill has 59 Senate co-sponsors, it has been bottled up in the Senate Judiciary Committee for months. According to one gun lobby source, Knox had promised the membership that the bill would be on the floor of the Senate by the time of the group's annual convention in Philadelphia earlier this month.

The NRA also has been unsuccessful in its efforts, both legal and legislative, to overturn an ordinance the Chicago suburb of Morton Grove, Ill., passed last year, banning possession and sales of handguns.

Knox led a drive to get the Illinois Legislature to do away with the state's local home rule option on gun ordinances, but the NRA-sponsored bill failed this month.

The NRA is known among gun enthusiasts as a hotbed of ogranizational infighting and intrigue, given to periodic leadership purges. Knox, an expert marksman who is credited with helping transform the group from an association of sporting shooters into a modern lobbying juggernaut, gained his position in 1978 after such a shakeup.

He is known to friends and adversaries as an agressive--some say abrasive--advocate. One adversary, Michael Beard, director of the National Coalition to Ban Handguns, expressed surprise at the reported firing.

"It's been a bad stretch for them, but I'm surprised," Beard said. "Neal Knox is a very effective lobbyist and political operative."