Oh, where to begin?
The Remington Model 8, born of John Moses Browning's 1905 patent for an autoloading rifle. Deemed the first successful commercial autoloading rifle in the U.S., although Standard Arms made a gas-operated Model G rifle about the same timeframe. Here's a bit of online history:
http://www.manions.com/trendline/217trendline/rem.htm
The Model 8, and later 81, are long-recoil actions, much like the Auto 5 shotgun. The difference with the rifle is that it's fed from a non-detachable box magazine, and has an outer barrel shroud, in which the barrel reciprocates during it's recoil and return to battery.
All Remington Model 8's and 81's are takedown, the forend comes off easily, and the forward receiver and barrel assembly is attached to the rear receiver via a bolt with folding handle.
The rifles, over the years, came in .25 Remington, .30 Remington, .32 Remington, .35 Remington, and (later) .300 Savage. The .25 through .32 calibers were pretty close copies of the Winchester centerfire rounds of the same caliber, but the Remington versions were rimless for better feeding from the box magazine. In a pinch, if you need brass for the Remington rimless rounds, you can use .30-30 Winchester brass, and lathe-turn down the rim, while deepening the extractor groove. (Ask me how I found this out!) The .35 Remington is a different beast, somewhat larger in case diameter, but still popular and available as commercially loaded ammo. The .35 Remington was offered in Marlin leverguns, which is probably why it's still available.
There's quite a bit of history involving a couple folks named Bonnie and Clyde, and a lawman named Frank Hamer, who took a shine to the Remington Model 8 as his go-to gun. Rather than attempt to re-post it here, I'll just give a URL illustrating it:
http://www.geocities.com/gator2856/frankhamer.html
and another site:
http://www.manions.com/trendline/216trendline/bonnie.htm
The gun became a favorite of law enforcement, and was offered with an extended-capacity magazine for that purpose. Some of these guns are still around, I think Tony has one in his collection. They look like this:
I've got two of these guns, one is a 1906-vintage Model 8 in .32 Remington. It was a yard sale wreck, complete with cracked stock, shortened butt, and cheap recoil pad. But the bore was pristine, so with a little extra wood from Fajen, some TLC with stain and linseed oil, and a beautiful re-bluing job brought it to this condition:
That's a Lyman #2 rear peep sight, which is probably worth more than the gun. Note, there are no external magazine guide springs on this rifle, those came later in the production run.
My second Browning-patent Remington Autoloader is a Model 81 in .300 Savage. It's currently undergoing restoration, again, with replacement Fajen wood. (Thanks, Tony Rumore of Tromix Corp!)
Now, something to pay attention to. The early Remington Model 8 rifles did not have a firing pin rebound spring. This means that when you chamber a round, make damned certain that the bolt strips the round from the magazine. DO NOT simply place a round in the chamber and let the bolt fly forward with the bolt release knob/follower catch on the left side of the receiver - you risk a slamfire. Been there, got that soiled underwear. Matter of fact, even when you do chamber a round correctly, if you don't fire it and safely eject it, take a look at the primer. There will be a slight dimple, reminiscent of M1, M14, and M16 ammo.
The later Remington Model 81's took care of this potential problem by installing a firing pin rebound spring inside the bolt, around the firing pin. My early Model 8 doesn't have the clearance around the firing pin for that spring, so I just make certain I load it from the box magazine each and every time, with the muzzle pointed in a safe direction.
My Model 8 in .32 Remington is surprisingly accurate, easily inside 2.5" at 100 yards with my 170gr handloads. I lucked out and fell into a stash of unfired, virgin .32 Remington brass from an estate sale. Remington will, every now and then, make a run of .30 Remington brass, and that can be used for the .25 and .32 Remington versions. For the .35 Remington, brass isn't really a problem.
Neat thing is, the Remington autoloader loves cast bullets, I run 170gr hard cast gas-checked in my Model 8, and it cycles and feeds them just fine.
Notice the safety lever? Kalashnikov probably did, too!
Parts are out there, you have to dig for them. I have a spare barrel in .30 Remington, and a spare main barrel shroud buffer spring. If you cannot find what you're looking from from Numrich (Gun Parts Corp) then I'd suggest Poppert's.
For an owner's manual, just give Remington a call. Believe it or not, they sent me, free of charge, not only a photocopy of the original owner's manual for my Model 8, but also several pages from the Remington 1910 catalog, displaying the various grades and chamberings for the Model 8.
I have the takedown and exploded diagram for the Model 8 and 81 in electronic format if you need it.
Hope this helps, it was a bit long-winded, but can you tell I am partial to the vintage Browning autoshucker?