America’s newest nuclear bomb built seven months early

• The U.S. has fast-tracked production of its latest nuclear gravity bomb with the first unit completed seven months ahead of schedule. The B61-13 replaces some older B61-7 models and offers improved flexibility for targeting.
• The B61-13 incorporates the same safety and accuracy systems as the B61-12, ensuring a high level of reliability and effectiveness.
• The National Nuclear Security Administration (NNSA) is shifting focus to building the B61-13 using the same manufacturing infrastructure as the B61-12.

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The U.S. has fast-tracked production of its latest nuclear gravity bomb, the B61-13. It completed its first unit seven months ahead of schedule, according to Sandia National Laboratories.

The B61-13 plays a key role in a broader modernization effort that aims to maintain a credible nuclear deterrent in an increasingly complex global security environment.

The B61-13 is a variable-yield gravity bomb with a reported maximum explosive yield of 360 kilotons. It’s widely described as roughly 18 times the strength of the 20-kiloton “Little Boy” atomic bomb dropped on Hiroshima. Unlike missile-launched warheads, the B61-13 is designed to be dropped from aircraft. This includes the B-2 Spirit stealth bomber and the upcoming B-21 Raider.

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Sandia credited the accelerated timeline to an “aggressive” plan that cut production time by more than 25%. The laboratory said the program prioritized test coordination with the U.S. Air Force, Los Alamos National Laboratory and the National Nuclear Security Administration (NNSA).

What’s different about the B61-13?

The Pentagon first announced the B61-13 in October 2023. It said the missile would replace some older B61-7 models and offer improved flexibility for targeting hardened or wide-area military assets. According to the Department of Defense, the B61-13 uses the same safety and accuracy systems as the B61-12. It also not increase the overall size of the U.S. nuclear stockpile.

Officials said the B61-13 is part of a planned modernization effort to keep pace with an increasingly competitive nuclear environment.

According to the 2022 Nuclear Posture Review, the U.S. is adapting its deterrence posture to match emerging threats from adversaries expanding and modernizing their own arsenals.

From B61-12 to B61-13: A planned transition

On Dec. 18, 2024, the NNSA completed the final production unit of the B61-12 Life Extension Program. The program refurbished and replaced older variants, including the B61-3, -4, -7 and -10. The B61-12 extended the bomb’s life by at least 20 years and incorporated a modern tail kit for improved precision. According to the NNSA, the program’s on-schedule completion demonstrated its ability to meet DOD needs at the required pace and scale.

NNSA, with B61-12 production now complete, has shifted focus to building the B61-13. It uses the same manufacturing infrastructure. The agency reported that early coordination across the nuclear security enterprise accelerated the B61-13’s production timeline, moving full-scale production from fiscal year 2026 to an earlier date.

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A broader modernization effort

The B61-13 is one of several active warhead modernization programs underway. Officials said these efforts aim to enhance capabilities and revamp the manufacturing base needed to support future deterrence missions.

Deputy NNSA Administrator Marvin Adams said the early delivery of the B61-13’s first unit “demonstrates our ability to execute — not only to our partners and stakeholders in DOD and Congress but also to our adversaries and allies.”

He added that the program’s success contributes directly to U.S. deterrence and assurance efforts.