In the early 1970s I was given a No 1 MkIII SMLE which was pretty much full size but made of plastic - and would chamber a NATO 7.62 case.The company was LS. In the '70s I constructed their Colt 1911, P38, P08 Artillery, S&W Combat Magnum and Broomstick Mauser. All 'functioned' as per the real thing and looked reasonably realistic.
Looks like you can still get them, if you want to pay stoopid money.
Items in LotsofModels store on eBay !