8:52 AM -- Law enforcement sources tell TMZ ... T.I. was, in fact, allowed into his gated community after an initial argument with the guard, but then returned on foot shortly afterward to confront the guy again. That's when cops were called to the scene, and ended up arresting him.

We're also told T.I. did NOT make physical contact with the security guard, but the guard feared he would be hit during the dispute. Under GA law, that constitutes an alleged simple assault.

T.I. got busted at his own gated community in Georgia after he got into it with a security guard for the neighborhood.

According to local reports, the rapper was trying to get to his house Wednesday morning -- around 4 AM -- but didn't have his key. T.I. and a friend argued with the guard at the security shack, who wouldn't let them enter ... and it got heated enough that cops showed up.

Henry County PD arrested Tip for simple assault, disorderly conduct and public drunkenness. He certainly doesn't look too pissed in his mug shot.

He's already been released ... without bail.