With less than 24 hours before the Military Times Battle Bracket field shrinks from 32 to 16, voters are running out of time to save some well-known pieces of military hardware from elimination.

Here’s a look at some of the closest contests, but no lead is safe — click here to cast ballots in all 16 second-round showdowns, and share your favorites on social media with the hashtag #BattleBracket.

(Vote totals as of Monday afternoon; Round 2 voting closes at 3 p.m. Eastern on Tuesday.)

F-22 Raptor (53.8 percent) vs. F/A-18 Hornet series (46.2 percent)

The winning air frame gets bragging rights among the fighter-jet set, plus a likely date with the AH-64 Apache helicopter in the third round. Number-crunchers can get their fill here and here.

Despite the bracket’s basketball theme, the NBA isn’t any help: The Toronto Raptors and the Charlotte Hornets split their two meetings this season and won’t face off again until April.

Close-In Weapons System (54.5 percent) vs. Aegis combat system (45.5 percent)

The Aegis system bounced shipboard coffee in the opening round, while the CIWS had no problem dispatching the Mk 45 deck gun. The matchup comes down to a matter of preference: Aegis’ ability to score a single hit against a satellite or incoming missile versus the ability of the CIWS to pump 3,000 (significantly smaller) rounds, at least, into any threat.

The ballistic battle should continue in Round 3, with the winner of this contest likely to fact the Tomahawk missile.

Marine “knife hand” (55.9 percent) vs. M2 machine gun (44.1 percent)

“Ma Deuce” leaped out to a strong start, but the Marine Corps faithful rallied to bring the knife hand even and then push it into the lead.

Not familiar with this gesture’s brand of military mythology? Click here for some more details, visit Terminal Lance for a slightly profane primer, and check out this 2013 White House petition, which lobbied for the knife hand to “become an official method of communication” for the Marine Corps. It topped out at 866 signatures.

M777 howitzer (57 percent) vs. Bradley Fighting Vehicle (43 percent)

Towed destruction has outpaced troop transport in the early going, but there’s plenty of time for Bradley fans to turn the treads around.

The winner is on a collision course with the Abrams tank, while the rest of the region seems heading for a Stryker-Cougar showdown in the next round.

Ohio-class submarine (58.9 percent) vs. USS Constitution (41.1 percent)

a major makeover