First, I think you mean a Model 54 or Model 70, and at least the latter came in 7X57mm Mauser, same round as the .275 Rigby, Rigby's patented bullets being the only difference. I think Model 54 was also made in 7mm; will check..

The Model 25 Winchester is rather obscure, but I think it was a solid frame (not take-down) version of the Model 12 pump shotgun. Where did you get that model in your head for a 7mm rifle?!

Next, her books are set in Kenya in the 1920's, so a Model 70 was out of the question. It wasn't made until 1937!

Mrs. Arruda credits me as a firearms consultant in her later books, which I deeply appreciate. But she was pretty stubborn about wanting Colt and Winchester arms, those being probably the only iconic American brand names she knew. Like most academics, she is woefully ignorant of firearms.

Because Rigby, H&H, Westley Richards, Mauser, Mannlicher-Schoenauer, etc. were widely used in her setting, I'd have preferred one of them, as they were technologically more advanced than US rifles of the day. A sporting version of the Lee-Enfield .303 would also have been a very likely choice for her characters. In fact, she did have a British lord use a Mannlicher. A Springfield sporter would fit.

I wrote 33 stories on FanFiction.net Most were about a TV show, "Sir Arthur Conan Doyle's The Lost World." One was a "Criminal Minds" fic, but made more authentic than the TV show, while remaining in character for the BAU and a plausible case. In these, I was very careful to use appropriate firearms and other items.

For instance, the characters drink tea from British firms in business then, enjoy Canada Dry ginger ale only after I confirmed that it has been made since 1907, and the guns, cars, animals, etc., are all very realistic for the times and places. I did have character Finn exchange her little crossbow for firearms,all types she could acquire in the circumstances.

BTW, these fics were for average readers, so I did not specify that her S&W M&P .38 was a Model of 1905, 4th Change, made late enough to have had a heat treated cylinder and Made in USA marked on the frame. That would be too technical for most readers. But I thought about the exact one she'd carry and even had it use the gold medallion stocks used by guns made a few years before. I thought I'd explain that if I had to by saying that S&W had found a barrel of older grips and used them a few years after they were no longer made. A very real possibility, as the company used older parts rather than discard them.

I may check on your M-25 Winchester, but am almost certain that it was a variant of the M-12 shotgun. I think Elmer Keith mentioned it in,"Shotguns." I'll dig out my copy and see. BTW, in my fan fiction, I did have, "Lost World" character Ned Malone use a M-54 Winchester in .270 and a Griffin & Howe .30-06, but only after the explorers had left the Plateau, married, and were on safari. By then, 1928-29, the M-54 was available, and Ned might well have wanted to try the new high velocity .270. His friends used .275 Rigbys and a .318 Westley Richards in that role, and had sporting .303's and heavier rifles for larger game. Finn got a Westley Richards .450/.400 for her heavy rifle, and others had .465 H&H and .500 double rifles, and Lord Roxton had the .416 he used on the TV show.

I know firearms quite well, and always proofread material at least three times before publishing. So, I was horrified to read several years after I posted one story that Ned had a Griffen & Howe rifle, not a Griffin & Howe! No one caught the error, but I did and was frustrated and embarrassed. And by then, I could no longer edit that story

Errors occur to all of us. Some are caused by sloppy proofreading or research. Others by typesetters.