or ▁John ▁Gar and ▁developed ▁an ▁" en ▁b loc " ▁clip ▁system ▁that ▁allowed ▁am mun ition ▁to ▁be ▁inserted ▁from ▁above , ▁clip ▁included , ▁into ▁the ▁fixed ▁magazine . ▁While ▁this ▁design ▁provided ▁the ▁requ is ite ▁flush - mount ▁magazine , ▁the ▁clip ▁system ▁increased ▁the ▁rif le ' s ▁weight ▁and ▁complexity , ▁and ▁made ▁only ▁single ▁loading ▁am mun ition ▁possible ▁without ▁a ▁clip . ▁ ▁E jection ▁of ▁an ▁empty ▁clip ▁created ▁a ▁distinct ive ▁met all ic ▁" ping ing " ▁sound . ▁In ▁World ▁War ▁II , ▁it ▁was ▁rum ored ▁that ▁German ▁and ▁Japanese ▁inf antry ▁were ▁making ▁use ▁of ▁this ▁noise ▁in ▁combat ▁to ▁alert ▁them ▁to ▁an ▁empty ▁M 1 ▁rif le ▁in ▁order ▁to ▁catch ▁their ▁American ▁enemies ▁with ▁an ▁un loaded ▁rif le . ▁It ▁was ▁reported ▁that ▁the ▁U . S . ▁Army ' s ▁Aber de en ▁Pro ving ▁Gr ound ▁began ▁experiments ▁with ▁cli ps ▁made ▁of ▁various ▁pl ast ics ▁in ▁order ▁to ▁soft en ▁the ▁sound , ▁though ▁no ▁improved ▁cli ps ▁were ▁ever ▁adopted . ▁However , ▁this ▁claim ▁regarding ▁the ▁ris ks ▁of ▁a ▁ping ing ▁empty ▁clip ▁is ▁question able ▁due ▁to ▁he ars ay ▁produced ▁as ▁fact ▁by ▁the ▁only ▁known ▁source , ▁the ▁otherwise ▁fairly ▁reliable ▁author ▁Roy ▁F . ▁Dun lap ▁in ▁Or dn ance ▁W ent ▁Up ▁Front ▁in ▁ 1 9 4 8 . ▁According ▁to ▁former ▁German ▁soldiers , ▁the ▁sound ▁was ▁in aud ible