A bunker buster bomb’s weight isn’t just a figure; it’s a calculated force intended to penetrate hardened geological formations and layers of steel-reinforced concrete. The heaviest conventional bomb currently in use is the GBU-57 Massive Ordnance Penetrator, or MOP for short. It weighs an incredible 30,000 pounds. It was created by Boeing and is only used by the B-2 Spirit stealth bomber. It is unique in that it combines precision and mass.
The MOP’s casing is made of an incredibly resilient Eglin steel alloy thanks to advanced metallurgy, which enables it to withstand high-velocity impacts into fortified terrain before detonating. Only roughly 5,342 pounds of the bomb’s weight is explosive, despite its enormous size. This ratio demonstrates how the bomb’s ability to penetrate is primarily due to kinetic energy transferred through dense structural momentum rather than the blast. Practically speaking, it’s similar to breaking through a granite wall with a freight train.
Bunker Buster Bombs and Their Weights
| Bomb Model | Weight (lbs / kg) | Key Use Case | Aircraft Used |
|---|---|---|---|
| GBU-57 MOP | 30,000 lbs / 13,600 kg | Deep underground facilities and nuclear bunkers | B-2 Spirit |
| GBU-28 | 4,000–5,000 lbs / 1,800–2,300 kg | Hardened command bunkers, Gulf War targets | F-15E, B-52 |
| Disney Bomb (WWII) | 4,500 lbs / 2,000 kg | U-boat pens and super-hardened structures | Lancaster Bomber |
| Grand Slam (WWII) | 22,000 lbs / 10,000 kg | “Earthquake” shockwave destruction under target | Avro Lancaster |
| KAB-1500L-Pr | 3,300 lbs / 1,500 kg | Russian deep penetration into concrete/soil | Su-24M, Su-34 |
| BLU-113 | 4,400 lbs / 2,000 kg | GBU-28 variant for hardened underground targets | Various USAF Aircraft |
| BLU-127 | 27,125 lbs / 12,304 kg | Core of the GBU-57 MOP design for maximum penetration | B-2, B-21 (future) |
For historical context, the design logic of Barnes Wallis’ World War II “Grand Slam” bomb is remarkably similar. The foundations of fortified targets were undermined by shockwaves from that 22,000-pound weapon. With precise GPS guidance, electronic fuzing, and a weight class that significantly outperforms its predecessors, the MOP modernizes this idea decades later.
The GBU-57 saw its first operational use in the June 2025 airstrikes on Iran’s nuclear facilities in Fordow and Natanz. Fourteen MOPs were dropped by seven B-2 bombers on targets believed to be buried more than 80 meters below the surface. Because of its exceptional weight, the bomb was able to penetrate deeply into solidified ground, reaching depths that conventional explosives were unable to reach. Analysts claim that this was a clear demonstration of capability rather than merely a tactical choice.
The guidance package for the MOP is made for high-altitude deployment and mid-air stability. Instead of planar fins, which are small but very effective at high speeds and altitudes, it uses grid fins. More control over the descent is made possible by this aerodynamic system, particularly when dropping a large object from more than 30,000 feet. Bunker floors collapse as a result of the bomb’s explosion, which does more than just bring down buildings; it also compresses the ground underneath them.
Without a corresponding increase in blast radius, the MOP offers exponentially more impact than lighter bunker busters like the GBU-28, which weighs roughly 5,000 pounds. This is especially useful for hitting deep targets without needlessly destroying the surface. It conveys an equally powerful psychological message: if the physics are in your favor, no bunker is too deep.
The development of such weapons is still guided by the “weight over yield” principle. Weight has become a deciding factor in the context of changing threats and high-stakes diplomacy. Although other nations have begun creating comparable instruments, none of them are as large as the MOP. Despite its effectiveness, Russia’s KAB-1500L-Pr is less than one-eighth as heavy and has a more constrained range. The BLU-113 and other American-made weapons are used in Israel’s own bunker buster programs.
Curiously, the target’s construction and geology also affect how effective heavy bombs like the MOP are. For instance, layers of ultra-high-strength concrete, some with a compressive force of over 30,000 psi, shield Iranian facilities. The question of whether even the MOP can always succeed has been raised as a result of this. The MOP is unquestionably a game-changer in aerial strategy, though.
The performance of the bomb has been significantly enhanced by the United States through the integration of smart fuzing systems. The Hard Target Void Sensing Fuze (HTVSF) is one such device that can postpone detonation until an air pocket or cavity is found; this means that it will only detonate when it is well inside the usable area of a bunker. It’s a very good illustration of how brute force and technology can coexist in a single device.
Beyond technical aspects, the social and ethical ramifications of these bombs are becoming more widely recognized. They are tactically invaluable, politically sensitive, and logistically complex due to their weight. The ability to breach subterranean facilities that safeguard nuclear enrichment, chemical weapons, or strategic command has both military and moral ramifications during conflicts. It forces both sides to think about how far they can go in hiding.
The upcoming B-21 Raider, which is expected to be the second aircraft that can deploy the MOP, will probably increase its role. Because it would enable more extensive strategic coverage without exclusively depending on the B-2 fleet, that change is especially encouraging. That combination of penetrative weight and aircraft flexibility could influence conflict resolution or deterrence in the years to come.
