9 3 9 , ▁and ▁a ▁version ▁with ▁a ▁ 5 - round ▁magazine ▁was ▁about ▁to ▁be ▁market ed . ▁But ▁when ▁German ▁arm ies ▁inv aded ▁Poland , ▁these ▁plans ▁were ▁delayed ▁to ▁increase ▁production ▁of ▁b olt - action ▁rif les ▁and ▁machine ▁guns . ▁ ▁The ▁German ▁invasion ▁of ▁Belg ium ▁in ▁May ▁ 1 9 4 0 ▁interrupted ▁any ▁plans ▁for ▁the ▁production ▁of ▁the ▁new ▁model , ▁as ▁Li ège , ▁home ▁of ▁F N ' s ▁factory , ▁was ▁occupied ▁by ▁the ▁German ▁military . ▁Despite ▁this ▁set back , ▁Sa ive ▁was ▁able ▁to ▁escape ▁to ▁England ▁via ▁Portugal ▁in ▁ 1 9 4 1 , ▁where ▁he ▁continued ▁work ▁on ▁what ▁would ▁become ▁the ▁F N - 4 9 . ▁ ▁By ▁ 1 9 4 3 , ▁Sa ive ▁was ▁back ▁to ▁working ▁on ▁his ▁experimental ▁rif le , ▁now ▁in ▁ 7 . 9 2 × 5 7 mm ▁M aus er . ▁Late ▁that ▁year , ▁the ▁Royal ▁Small ▁Ar ms ▁Factory , ▁En field ▁ordered ▁ 5 0 ▁pro tot ypes ▁( design ated ▁" EX P - 1 " ▁and ▁sometimes ▁referred ▁to ▁as ▁" S LE M - 1 " ▁or ▁" Self - Loading ▁Ex perimental ▁Model "). ▁Based ▁on ▁tests ▁with ▁these ▁pro tot ypes , ▁En field ▁placed ▁an ▁order ▁for ▁ 2 , 0 0 0 ▁rif les ▁for ▁tro op ▁tri als , ▁but ▁a ▁last - min ute ▁problem ▁with ▁the ▁moder