The 243 Win. ( I assume) and the 6mm are both the same caliber but different cartridges if I’m not mistaken. I’m looking into getting the 6mm Rem. for deer and for varmint. Something with low recoil but heavy enough for deer if I so choose. Using a good bullet such as the Barnes or Nosler would not be to small in the 243 caliber. I have no experience but from what I have been reading it should do fine.