▁as ▁n yl on ▁and ▁T ef lon ▁have ▁been ▁used , ▁with ▁limited ▁success , ▁especially ▁in ▁rif les ; ▁however , ▁h ollow ▁point ▁bul lets ▁with ▁pl astic ▁aer od ynamic ▁tips ▁have ▁been ▁very ▁successful ▁at ▁both ▁impro ving ▁accuracy ▁and ▁en han cing ▁expansion . ▁Ne wer ▁pl astic ▁coat ings ▁for ▁hand gun ▁bul lets , ▁such ▁as ▁T ef lon - co ated ▁bul lets , ▁are ▁making ▁their ▁way ▁into ▁the ▁market . ▁▁ ▁Sol id ▁or ▁Mon ol ith ic ▁Sol id : ▁mon o - met al ▁bul lets ▁intended ▁for ▁deep ▁pen etr ation ▁in ▁big ▁game ▁animals ▁and ▁sl ender ▁sh aped ▁very - low - drag ▁project iles ▁for ▁long ▁range ▁shooting ▁are ▁produced ▁out ▁of ▁met als ▁like ▁o xygen ▁free ▁co pper ▁and ▁allo ys ▁like ▁co pper ▁nick el , ▁tell ur ium ▁co pper ▁and ▁br ass , ▁for ▁example ▁highly ▁mach in able ▁U NS ▁C 3 6 0 0 0 ▁Free - C ut ting ▁Br ass . ▁O ften ▁these ▁project iles ▁are ▁turned ▁on ▁precision ▁C NC ▁l ath es . ▁In ▁the ▁case ▁of ▁sol ids , ▁and ▁the ▁rug ged ness ▁of ▁the ▁game ▁animals ▁on ▁which ▁they ▁are ▁used , ▁e . g ., ▁the ▁African ▁buff alo ▁or ▁ele ph ant , ▁expansion ▁is ▁almost ▁entirely ▁rel in qu ished ▁for ▁the ▁necessary ▁pen etr ation . ▁In ▁shot g unning , ▁" slug " ▁loads ▁are ▁often