Weapon H, like Wolverine, may have adamantium-coated bones, but the Hulk-Wolverine hybrid hero's metal insides work pretty differently than Logan's. Marvel Comics created Weapon H to be the combination of several heroes, most notably Wolverine and the Jade Giant. However, when the Hulkverine transforms from his human-like form to his Hulk form, his entire body shifts, with nanotech allowing him to change sizes despite metal inside covering his bones.
Weapon H is one of Marvel's strangest and most powerful experiments, as the Weapon X program created the hero by combining the DNA of the future version of Logan and Amadeus Cho's Hulk. The former mercenary Clay Cortez transformed into the Hulkverine, whose DNA also consisted of a few other heroes and villains, including Sabretooth, Domino, and Warpath. But, thanks to Lady Deathstrike's DNA being included, Weapon H was embedded with nanotechnology throughout his bloodstream. As a result, the Wolverine-Hulk hybrid hero could Hulk out despite having his bones covered in adamantium. The upgrade put Hulkverine in a league of his own when it comes to manipulating the adamantium coating on his bones.
In Weapon X #7 by Greg Pak, Fred Van Lente, Marc Borstel, Ibrain Roberson, Frank D'Armata, and VC's Joe Caramagna from Marvel Comics, the Weapon X team (who adopted the name of the organization who experimented on them) led by Wolverine try to find Weapon H after he turned on his creators. After tracking him, they realize his footsteps got smaller, as he turned into a human. Sabretooth asks how that's even possible, considering Weapon H has adamantium bones, but Lady Deathstrike suggests perhaps the nanotech from her cybernetics allows him to shift his bones even with the metal covering them.
The Hulk-Wolverine hybrid would be instantly killed without the nanotech every time he transformed, as his adamantium-coated skeleton would be ripped from his body every time he Hulked out. However, with the nanotech, Weapon H's body can shift as needed allowing him to change back into Clayton Cortez when required. Although, recently, his nanotech has led him to take an even more unusual form, as the Hulkverine became a Red Hulk-like Harpy creature in the most recent issue run of the Savage Avengers after traveling through time.
Given that he's the blend of several heroes and villains, Weapon H can do things Wolverine can't including being able to transform from human to Hulk or vice-versa, despite having his bones coated in adamantium. Weapon H's amazing transformations is all due to Lady Deathstrike's nanotechnology being embedded in him. Ultimately, it's another power that separates the Hulk-Wolverine hybrid hero from the powerful heroes he was designed from.
