Not sure bout the 12guage pump. Coulda swore the one they had in the making of and design vid was a Benelli m2. And they didnt screw up the name and aliver like you say, the M87ELR isnt a Mauser. I can't think of the name right now but it is a real .50 bolt action rifle.
Good list though, I always laugh when idiots in game try claiming guns are something else, most common is people say the M18 isnt a glock or the 226 isnt the Sig.