"Deadly Business" is a polemic, worthy of Michael Moore. The fact is that there was nothing unusual or sinister about the importation of those Carcano rifles any more than about any of the other milsurp imports at the time. It was all legal and approved right down the line.
As to GCA 68 it is true that the assassinations of the Kennedys gave it an impetus. But the real reason was the riots that followed the assassination of Dr. Martin Luther King, Jr. Congress looked out from Capitol Hill at a burning capital, thought of what would happen if all those black hands had mail order guns, and went berserk with racism. The big selling point of GCA 68 was that the buyer of a gun would have to come "face to face" with the seller. No seller can tell a criminal by his face, but he can surely tell a black person. Since it was assumed that the government would never allow a black person to have a dealer's license, the goal was to keep white dealers from selling to black "revolutionaries".
As to Congressional reaction to the JFK killing, the folks here have vastly understated it. Hysteria and insanity were the order of the day. Laws were proposed to ban all guns, all rifles, all scope sights, all military guns, and on and on. There were proposals to put NRA members in concentration camps, and to exterminate all gun owners without trial. There were probably over a thousand anti-gun bills introduced in Congress in the next few days. GCA 68 was a watered down amalgamation of them.
Not commonly known casualties of the JFK tragedy were planned DCM sales of M14 rifles, welded to semi-auto National Match configuration (M14M), and sales of Model 1903A4 rifles with the original scope sights; the scopes were removed, broken up, and the lenses given to high schools for "science projects".
Jim