James J. Barney, codename Grand Slam, is a weapons engineer and G.I. Joe's resident expert on reverse engineering extraterrestrial technology. Unfortunately he hasn't had the best luck with not getting shot out in the field. On the most recent occasion, Grand Slam was left paralyzed from the waist down, confining him to a wheelchair. Now unable to be part of the active G.I. Joe field roster, Grand Slam harbors a serious grudge against Rock 'n Roll, the man responsible for his injury, and has overall become grouchy and paranoid that his new disability has put his status as a member of G.I. Joe in jeopardy.
James J. Barney was born in Chippewa Falls, Wisconsin. Growing up, he became a fan of science fiction and found himself fascinated by the laser guns and various other weapons and tools used by the characters in these kinds of stories. Though he still dreamed of more technologically advanced fare, he eventually developed an interest in real world weaponry as well, something that would lead to him joining the military. During his time in the Army, Barney graduated from the schools for Special Weapons, Artillery, and Advanced Tech and would prove proficient in both operating and developing new forms of artillery. These skills, in addition to a remarkable knack for plotting trajectories, eventually earned Barney a place in G.I. Joe with the code name Grand Slam.
On one of his first missions with the team, Grand Slam was part of G.I. Joe Team Alpha on a mission to retrieve stolen network files from the Ichkerian mafia. When the Joes were found out, Grand Slam was shot in the head by a sniper but miraculously wasn't struck anywhere fatal, allowing him to make a full recovery and remain a member of G.I. Joe.
Apparently unaware that he had survived, Duke kept a picture of Grand Slam in his wallet along with several photos of dead Joes.
At the time of G.I. Joe's recommissioning in 2016, Grand Slam was stationed at the Earth Defense Command base at Bikini Atoll while waiting to be cleared for combat. While there, Grand Slam put his technological expertise to work in aiding the EDC's efforts to repair the Decepticon defector Skywarp's out of control teleportation systems. Though he was able to fix the problem that was causing the Cybertronian to come out of phase, he also left Skywarp unable to teleport at all. While he poked around inside him, Grand Slam also began to develop an understanding of Cybertronian laser weapons and used that understanding to build his own laser rifle.
When the EDC base was infiltrated and taken over by the Dire Wraiths, Grand Slam was the only human at the facility who managed to survive. Holing up with and defending Skywarp, Grand Slam fended the aliens off for two days before a team led by Scarlett arrived to investigate why the base had gone dark. When Rock 'n Roll finally found Grand Slam's hiding spot, Slam brandished his laser rifle at his former teammate, believing him to be one of the Wraiths. Despite Rock 'n Roll's insistence that he was who he said he was, Grand Slam refused to stand down, forcing Rock 'n Roll to shoot him. While he was able to survive yet another seemingly fatal gunshot wound, this one left Grand Slam paralyzed from the waist down, confining him to a wheelchair.
Despite his injuries, Grand Slam remained part of G.I. Joe, stationed aboard the team's new underwater base Lemuria, and worked together with the Docs Junior and Senior on a device capable of detecting Dire Wraiths. As the elder Doc scanned his daughter and then himself, Grand Slam was frustrated to find the device reading both of them as Wraiths. Just then, Rock 'n Roll entered the lab wanting to talk with Grand Slam, who claimed he was far too busy to talk with him. When Rock told him all he really wanted was to be given a laser weapon like the rest of the Joes, Slam brusquely presented him with laser shotgun before wheeling off, reminding Rock that he was responsible for his current condition.
As he made more and more adjustments to his scanner, Slam continued to be confused why it still read Doc Senior as being a Wraith. Just as Doc suggested they take a break from it, Skywarp made his way into the lab, demanding that the two scientists finally get around to fixing his broken teleportation abilities. Though Grand Slam made no promises he'd be able to figure it out, he still agreed to take a look. Lifeline had stabilized Doc, Grand Slam asked what they would do. Skywarp opined that the Joes should kill the Wraith, but Grand Slam and Scarlett refused on the grounds that Doc was their good friend. When the younger Doc returned from the field and was promptly detained in her quarters, Slam argued with Scarlett over whether or not it was right for them to keep one of their own locked up. When Lifeline opined that they should be keeping her in the lab for study, Slam took offense and reminded him that Doc Junior was only half Wraith and that her father had saved his life.Just as Skywarp seemed at his wit's end with the two of them, Grand Slam finally gave him the go ahead to try teleporting again. However, something suddenly went wrong, causing the machine Skywarp was hooked up to to explode! As he shielded himself from the blast, Grand Slam was shocked to find Doc Senior revealing that he actually had been a Dire Wraith all along, assuming his true form as he dove to protect Slam from some incoming shrapnel. After Scarlett had been called to the scene and
In preparation for G.I. Joe's expedition to the center of the Earth to dispatch the Fatal Fluffies, Grand Slam and his team created the Mole Pods. While he presented these new vehicles to the field team, Slam was annoyed by Rock 'n Roll showering him with praise and told Rock to stop trying to kiss up to him.
Given that it wasn't as defective as it seemed, Grand Slam gave Scarlett a Wraith scanner for the field.
On Shipwreck's orders, Grand Slam built a pair of super powerful brass knucks that would bolster Gung-Ho's strength. After presenting them to Shipwreck, he excitedly asked Dial-Tone what his role on Ship's new quick response team only to fly into a rage when he found out he wasn't on it but guys like Rock 'n Roll and Skywarp were.
After Matt "Spectrum" Trakker of M.A.S.K. was made a member of G.I. Joe, Grand Slam visited his lab both to congratulate him on the work he and Cover Girl did on the team's newest vehicle and gripe at him about how he was going to replace him. Spectrum didn't quite understand what was bothering Grand Slam so much, forcing Slam to elaborate that now that the team had someone who was technically minded and field ready, he was effectively obsolete. Spectrum didn't agree and asked to take a look at Grand Slam's wheelchair to see if he could modify it so Slam could take a more active role. Slam shrugged off Spectrum's praise of his work on custom building the chair before Skywarp returned to the lab, asking yet again about getting his teleporter fixed. Though Grand Slam shooed him off, saying they still didn't have the materials necessary, Spectrum let it slip that they could change that pretty easily. After claiming they'd still be backordered and getting Skywarp to leave, Slam chewed Spectrum out for thinking it'd be a good idea to give a grouchy ex-Decepticon a teleporter.
- Given that Grand Slam's first appearance in the IDW continuity involved him getting shot in the head, many assumed his reappearance in Joe's Revolution tie-in was a new character who had inherited the codename until writer Aubrey Sitterson confirmed they were the same guy in the letters page of G.I. Joe vol. 5 #3. Funnily enough, Slam's "corpse" was carried off by Rock 'n Roll in his Origins appearance.