Lil Wayne -- Alleged Bus Shooter Goes Full Snitch ... Birdman Should Be Behind Bars!

The man charged with shooting up Lil Wayne's tour bus has blown the whistle on Birdman ... saying he should be behind bars too.

Jimmy Winfrey claims in new court docs he shouldn't be singled out for the crime, when "[Birdman's] financial dispute with [Lil Wayne] is what ultimately led to the shooting."

So, Winfrey argues, "[Birdman] should be held liable as a party to the crime." He's not specifically saying Birdman ordered the hit, but essentially that's what he's saying.

As TMZ first reported, Wayne's tour bus was shot up back in April as he was leaving a club gig in Atlanta.

Birdman denies any involvement.