▁it ▁to ▁perform ▁more ▁effectively ▁in ▁the ▁shorter ▁bar rel ▁of ▁the ▁XP - 1 0 0 . ▁ ▁The ▁. 2 2 1 ▁Fire ball ▁produces ▁the ▁highest ▁velocity ▁of ▁any ▁commercial ▁p istol ▁cart ridge . ▁ ▁Off sh o ots ▁ ▁The ▁. 2 2 1 ▁Fire ball ▁has ▁been ▁used ▁by ▁wild cat ters ▁to ▁create ▁a ▁small ▁efficient ▁. 1 7 ▁cal iber ▁cart ridge . ▁The ▁most ▁common ▁is ▁the ▁. 1 7 ▁Mach ▁IV ▁which ▁is ▁essentially ▁the ▁. 2 2 1 ▁neck ed ▁down ▁to ▁the ▁smaller ▁cal iber . ▁This ▁cart ridge ▁is ▁reported ▁to ▁have ▁a ▁very ▁flat ▁traject ory ▁and ▁to ▁be ▁relatively ▁quiet ▁with ▁low ▁re co il . ▁It ▁has ▁been ▁so ▁popular ▁as ▁a ▁wild cat ▁that ▁in ▁ 2 0 0 7 ▁Rem ington ▁legit im ized ▁it ▁by ▁introdu cing ▁their ▁own ▁version ▁only ▁slightly ▁different ▁from ▁the ▁Mach ▁IV ▁and ▁calling ▁it ▁the ▁. 1 7 ▁Rem ington ▁Fire ball . ▁ ▁A ▁. 2 0 ▁cal iber ▁version ▁is ▁also ▁gain ing ▁popular ity ▁called ▁the ▁. 2 0 ▁Var T arg ▁( V T ), ▁" v art arg " ▁being ▁the ▁combination ▁of ▁the ▁words ▁" var m int " ▁and ▁" target ". ▁The ▁. 2 2 1 ▁Fire ball ▁has ▁also ▁been ▁used ▁as ▁the ▁base ▁for ▁the ▁. 3 0 0 ▁Wh is per , ▁sometimes ▁referred ▁to ▁as ▁the ▁. 3 0 0 /. 2 2 1 ▁or ▁.