That .50 cal Browning at tank-modellbau.de looks to be only the barrel assembly. The rest of the MG in the picture is the receiver of the HL gun. I'm not sure what they're selling, a complete gun or just the barrel as an upgrade.

I would advise buying the .50 M2 sprue from the Tamiya M-26 as the best alternative because the stock HL molding leaves a lot to be desired and requires extensive mods to make it look right.