As to the Randy Weaver matter, there are lots of stories about what happened, with differing details, and none of them, including the sworn testimony at the trial are proven beyond doubt.
The story I heard, and consider most plausible, is that Weaver cut the barrels to legal length (18" or possibly 18.25"). The guy who wanted the barrels cut (and bought the guns after Weaver cut them) was an ATF informant, and that when he delivered the guns to the ATF agents running the case, the guns were measured and came up 1/4" short of the legal overall length. The entire matter resulting from that was horribly and tragically mishandled by the ATF and the FBI and Weaver's son and wife, and a US Marshal died as a result. Also remember that after the prosecutor literally walked out of court and quit during the trial, the Govt settled with Weaver, paying a bunch of money and "admitted no wrong doing".