Raynor began playing drums in his preteens, forming a group with friend Ryan Kennedy at age 11 to perform at a school competition – "a kind of 'show and tell' thing," Raynor later recalled. The duo were initially inspired by Metallica, but found their material far too technical; they instead played "Twist of Cain" by Danzig and "London Dungeon" by the Misfits. Raynor's first legitimate performance consisted of a cover of "Vlad the Impaler" by Gwar.
Raynor attended Rancho Bernardo High School (RBHS). RBHS often arranged Battle of the Bands competitions, and Raynor participated: his band, The Necropheliacs, played a cover of Metallica's "Creeping Death". While at the competition, new transfer student Tom DeLonge, who had been kicked out of Poway High School for attending a basketball game while drunk, performed an original song titled "Who's Gonna Shave Your Back Tonight?" to a packed auditorium. Raynor was introduced to DeLonge at a party by Paul Scott, founding member of The Necropheliacs, shortly before he moved out of state. The two found they had plenty in common, and DeLonge was searching for a more permanent band to create music with. The two began writing songs at Raynor's parents' home – "a strange mix of metal and Descendents-style punk" – and tried out a variety of bass players, according to Raynor. DeLonge later met Mark Hoppus in August 1992 through friend Kerry Key and his girlfriend, Anne Hoppus. "I thought they were hilarious when I met them. I mean, I didn't have a driver's license yet, so I gained a lot of agency through hanging with them and their group of friends," said Raynor. The trio began to practice in Raynor's room (amid complaints from neighbors), which was soundproofed with empty egg cartons.
The trio spent time together constantly, attending punk shows and movies and playing practical jokes. The trio first operated under a variety of names, including Duck Tape and Figure 8, until DeLonge rechristened the band "Blink". Hoppus' girlfriend later led him to depart from the group for a time, but he returned when Raynor and DeLonge began recording a demo tape on a four track recorder with friend and collaborator Cam Jones. The band soon became part of a circuit that also included the likes of Ten Foot Pole and Unwritten Law, and they found their way onto the bill as the opening band for local acts at SOMA, a local all-ages venue which they longed to headline. "It's difficult to describe, in words, the nauseous mix of fear and excitement that would hit me when I first started seeing lines of people wanting to hear us play," said Raynor.
The three eventually were playing concerts at local venues such as SOMA, which alerted local independent record label Cargo Music. Hoppus was the only member to sign the contract, as DeLonge was at work at the time and Raynor was still a minor. The Cheshire Cat sessions were to be the last performance with the band for Raynor, whose family had moved to Reno, Nevada. Raynor stayed with his sister for the summer of 1993 in order to rehearse for the recording of their debut album. Raynor moved to Reno following the recording and was briefly replaced by school friend Mike Krull. The band saved money and began flying Raynor out to shows, but eventually Raynor would move back to San Diego to live with Hoppus and his family. His parents allowed him to drop out of full-time school to move back and play with the band, but he would continue to finish his diploma by bringing homework on tour. "I think Mark and his sister Anne and I stayed up watching old TV shows until morning that whole summer," he recalled.
"The summer I lived with Mark and his family was probably the greatest summer of my life so far," said Raynor in 2001. "I left home at 17, came to San Diego, we bought a van, finished our first video… I had all kinds of dreams in my head and they were all coming true."
By March 1996, the trio began to accumulate a genuine buzz among major labels, resulting in a bidding war between Interscope, MCA and Epitaph. MCA's persistence and sincerity won the band over, as well as their promise of complete artistic freedom. The band began recording their sophomore effort Dude Ranch that winter. Raynor had broken both heels and was in a wheelchair due to a drunken stunt; he was well enough to record the drum tracks for the album while on crutches. The record hit stores the following summer and the band headed out on the Warped Tour, which Raynor described as "one of the most unequivocally positive experiences of my time with the band." When lead single "Dammit" began rotation at Los Angeles-based KROQ, other stations took notice and the single was added to rock radio playlists across the country. Desperate for a break due to extended touring, the overworked band began to argue and tensions formed, centering largely around Raynor.
Raynor had planned from the earliest days of the band to one day attend college, as he said in a partially tongue-in-cheek remark in a 1994 interview: "I don't want to be 30 and still in a punk-rock band. That seems kind of scary to me." Shortly after the band released Dude Ranch, Raynor began to think outside of the situation, viewing the major label experience as nothing like he had hoped. He had only been half invested in the band since signing to MCA, as he felt it offered less creative freedom, especially in comparison to Epitaph, which had been pursuing the band and was Raynor's first choice. "I mean, I was intellectually invested, I recognized it as a smart move financially. But it's like that song says, 'I Left My Heart in San Francisco'; I left my heart in the office at Epitaph. After that compromise I found it difficult to make further ones, and I felt like I was asked to make a lot. Eventually, there was not enough of my heart in the band to justify my sticking around. I backed away, I was dead weight." The tension came to a head in February 1998 as the band embarked on SnoCore, described as "a winter version of the Warped Tour." Sharing the stage with Primus, the band was enjoying more success than ever before, but the drama between the musicians had grown substantially. Relations reached a low point when the band engaged in a fight on a Nebraska date after SnoCore's conclusion. Shortly after the conclusion of SnoCore was a short minitour along the western coast, most notably Southern California, the band's favorite place to play. The tour ended with the band headlining a sold-out show at the Palladium in Hollywood, where the band had dreamed of performing for years.
Raynor suffered a "tragic loss" during the West Coast mini-tour and flew home, forcing the band to find a fill-in drummer: Travis Barker of the ska punk support band The Aquabats. Barker learned the drum tracks for the band's set in only 45 minutes prior to his first show. Raynor returned for the band's Hollywood Palladium performance, and the band became increasingly uneasy and arguments grew worse. To offset personal issues, Raynor began to drink heavily and it began to affect the band's performances. Following a largely successful Australian tour in the spring, Hoppus and DeLonge presented an ultimatum: quit drinking or go to an in-patient rehab. Raynor agreed to both and informed the band of his decision after taking the weekend to mull options. According to Raynor, he was fired through a phone call despite his agreement to rehab. Despite this, he felt no malice toward his former bandmates and conceded they were "right" to fire him.
The band would minimize the impact of the situation in future interviews and remained vague regarding his departure. The band later worked Raynor's departure into a song, "Man Overboard," which makes reference to his alcohol abuse.
Following his exit from Blink-182, Raynor kept himself busy with various musical projects, including a group called The Axidentals. Raynor played guitar for the group, which recorded an extended play and a full-length that was left unreleased when Vagrant Records showed interest in signing the band. By the time the deal went through, Raynor was having disputes with the group and quit; the band later released their debut album as Death on Wednesday through Vagrant in 2000. Raynor also began contributing to a charity called StandUp for Kids, an outreach organization that helped street and homeless youth. He also taught music to teens in trouble with the law under the Street of Dreams program.
Raynor later went on to perform with the group Grimby from 2000 to 2001, which recorded an extended play at Doubletime Studios. Recorded live over the course of a day, Raynor has described it as dark comedy, "a Black Sabbath, Ramones, and "Weird Al" Yankovic milkshake." In January 2003, a rumor circulated on the Internet that Raynor had been shot dead; he addressed the hoax via a letter he e-mailed to the sites in question, that instead directed the attention to the StandUp for Kids organization. Raynor fulfilled a long-held ambition to work with Nirvana producer Jack Endino on an extended play recorded with The Spazms in 2004. "The language of the whole record really speaks for me. It's deskilled, nihilistic, and posits, by default not intention, a Franco-feminism," he said.
As of 2017 Raynor is the drummer for The Los Angeles post punk band "The Wraith"