No, its just royal mail. AFAIK parcelforce will courier them, but RIFs are not in their T&C and will not cover them if they are lost or broken during transit.
See, this is where I'm confused, the RM parcel options list the biggest parcel they'll take at 60x40x40, not really big enough for a big gun...
Check restricted Item's, RM Will Take them But it Cost's more and you have to take it to a Post Office (I Posted a PARA M249 from one in my village =D)