I saw one in the Holland and Holland store in London in 2016. Talked to the staff for a good while about it. Apparently , an American client created it , because at the Time , H & H weren't doing .600 Nitro Express rifles anymore . So he was like " Okay , Make me a .700 ! ".
They then told him " Get us the cartridge and we'll build you a gun to handle it " . They thought he was not serious. Of course , next year , he returned with the .700 Nitro Express bullet. So they held up their end of the bargain. I actually got to hold it. Weighed 19 pounds or so ( probably close to 20 ) . I have ZERO intention of firing it ( I love my shoulder
).
The makers themselves told me that the only people who buy .700 Nitro Expresses are collectors or people looking for an investment or a conversation piece. Serious hunters view them as novelty things. Reports of their use in the 1980s showed poor penetration for the frontal head shot on Elephant.
I myself consider , among double rifles , the .500 Nitro Express to be the sweet spot for Express rifles. The .577 , .600 and .700 lack penetration compared to a .500 Nitro Express. The .500 Nitro Express Firing a 570 grain Full metal jacket bullet at 2150 fps will penetrate deeper than a .577 Nitro Express full metal jacket bullet at 2050 Fps .
I have an old 1980s era Article about the performance of the .700 NE in the field
If you like , l could inbox it to you