In this study we compute grain boundary (GB) properties for a large set of GBs in bcc transition metals with a special focus on W, Mo, Fe and W25at%Re using ab initio density functional theory (DFT) and semi-empirical second nearest neighbour modified embedded atom method (2NN-MEAM) potentials. The GB properties include GB energies, surface energies, work of separation and GB excess volume. We first identify the best simulation setup to evaluate these properties and then analyse them and compare them to various experimental data where we find a good overall agreement. In particular our results explain the experimental finding that W and Mo prefer intergranular fracture while other bcc metals prefer transgranular cleavage. We find that the used 2NN-MEAM potentials can predict general trends of GB properties but do not always reproduce the GB ground state structure and energy found with DFT.