Answers, mebbe...
OK, for the OP's question: (1) These rifles are worth owning. They are shootable Mauser k98K's in finge shape. (2) Shortcomings: As mentioned, no collector value due to Mitchell's "prettying up" process. Also, if what you want is a shooter Mauser 98, Mitchell's price is about $100 too high--that's what you're paying for the prettying up, plus all those Mitchell ads in gun mags, plus of course Mitchell's profit. (3) Commercial 8x57 JS ammo is available in just about any well-stocked local sptg gds sto, or online. (Also called 7.9x57 JS--same thing!) Military surplus 8mm is getting rare, and the price is going up. The American-made 8mm is loaded down because there are a few old "8mm" rifles around with .313" bores instead of the .323" that became standard prior to WWI. No MILITARY 8mm Mausers made since 1905 will have the small bore however, (check the date on the receiver of your k98K; strong odds are it'll be later than that; slug the bore if you're not sure), but the American ammo is loaded so it can't burst the old smaller-bore rifles. European commercial ammo is loaded hotter. And of course you can handload.
As has been pointed out, military rifles are made kind of klunky, so as to bear up to the mistreatment they get in battle and still shoot. IMHO, that doesn't make them worse than commercial rifles, just different. And if you want this rifle just for shooting, there are all sorts of retro parts for the 98 that you can get, and play with.
The Mitchell M-48's I know less about, but I think they are Mitchell-prettied also. And certainly Mitchell-priced. The M-48 (which was started in production in 1947, of course, just to keep things interesting) obviously never saw service in WWII, so it has no historical value. Parts are mostly not interchangeable with the k98K, BTW, tho' some are. You'll find several Cyrillic characters and the number "44" on the side of the receiver--This means "FACTORY # 44" where the M-48's were made, and is NOT a date of production. The M-48's maybe saw some police work or some such, but mostly they were just stored, so mostly they are in pretty good shape.
Were I you, I'd start going to gun shows in your area, and pricing k98's and M-48's, and handling a number of them. Bring a rag, you'll get an icky brown greasy preservative called cosmoline, on yourself. Pretty soon you'll get a feel for what is a bargain in your area, and mebbe develop a preference for one model. There are a plethora of military Mausers, not all are 8mm's, and identifying, classifying, and collecting them is a whole sub-genre all by itself among military rifle collecting.
Just as a final word, Mitchell's Mausers are overpriced, to put it bluntly. You can do better. The other side of that coin is, of course, that they're not making military bolt-action rifles any more, and the Mauser is among the best-designed bolt actions to be had.
Good luck and enjoy. Oh, and please keep us posted!
