This is the Gallus K from Gundam UC. It's a modified HGUC Gallus J.

As of this posting, there's no sign of the Gallus K being released, but the concept was "What if I built the HGUC kit straight out of the box?" I tried to make it as plain as possible, based on the anime design.

It's a derivative of the AMX-101 Gallus J, developed during the First Neo Zeon War.

Its fixed armament has been removed, and it's equipped with the Rats River triple missile pod (used on the Zaku Desert Type) and the Zaku Cannon's Big Gun on each arm as portable weapons.

It also has the AMX-00 on its shoulders.

AMX-101K Gallus K | トーナ's Gunpla works