Kim Zolciak Gives Daughter Brielle Handgun for 21st Birthday

Kim Zolciak's little girl is now a grown ass, pistol-packing mama, and her mom wouldn't have it any other way ... TMZ has learned.

Brielle Biermann turned 21 on Sunday, and when she got home on Monday ... Kim was waiting with her gift -- a brand new customized Glock 43, complete with rose gold slide. Brielle seemed a little nervous around the weapon at first, but Kim said it's important for her to have it ... now that Brielle's living in her own condo.

We're told Brielle's practiced at a gun range before. She doesn't have a license yet, but Georgia doesn't require one if it's stored in a home, car or place of business.

BB also got some pieces of art, which look like molds of topless women, and set Kim back $5,550 each! The handgun was a relative bargain at just $1,300.