Best mad bomber recipe imo is The MFC Cluster. Just scavenge all the Duct Tapes and Scrap Electronics you can find. MFC Cluster is like 6 independent throwable mines that do extreme damage. When they do not explode, you can recollect them as MFC grenades.
For an explosives build I'd always use all weight related perks (Strong Back, Burden to Bear, Pack Rat, Heavyweight and the Hoarder perk).