 Bull left Canada and moved to Brussels, where a subsidiary of SRC called European Poudreries Réunies de Belgique was based.Bull continued working with the ERFB ammunition design, developing a range of munitions that could be fired from existing weapons.A number of companies designed upgrades to work with older weapons, like the M114 155 mm howitzer, combining a new barrel from the M109 with Bull's ERFB ammunition to produce an improved weapon for relatively low cost.