I did find this infor on a different forum. I still wonder if this was a Remington factory stock job as the checkering is not all that great.

Default RAC M07/15 French Contract.
If the rifle is complete, it is worth more as a collectible than trying to "rebarrel" it.

The RAC M'07/15 is in the French M1886 8x51R Lebel cartridge, totally unlike any other "8mm" cartridge of Military design.

The Remington-made Contract firearms , most of which were never accepted by the French Army, due to parts Tolerance problems,& were eventually sold off in the USA during the 1920s, along with Remington made "8mm Lebel" ammo for them ( Boxer primed and reloadable).

As the rifles were brand new when sold, the "rust" on the rifling could be either due to the corrosive priming of the ammunition of the time(Remington only introduced Noncorrosive priming in the late 1920s, in commercial ammo, whilst its military contract ammo was all corrosive) and/or insufficent cleaning.

I would say try to clean thoroughly the bore of the barrel, using a good stiff brush, Hoppe's #9 solvent or "Sweet's 7,62" solvent (which removes rust and metal fouling) and then get some 8mm Lebel ammo (milsurp is still available here and there, but is Corrosive, and Berdan Primed; Buffalo Arms does make Formed new cases and ammo, and there are some other suppliers who have proper (New made) cases from Europe.(Graf's I think)...these can be loaded with Noncorrosive (Boxer) primers. Dies are available from RCBS and CH4D.

Rebarrelling is a very expensive option ( a gunsmith would have to make a completely new barrel, buy or make an 8mm Lebel reamer( as there is no other cartridge which will work through the mechanism, unless you change calibre up to .348 Winchester....in summation, you could spend up to $1,000 in Gunsmiths fees, and still not get a shootable rifle.

And then there are the charger packet clips...three-shot Berthier M07/15 clips are getting like Rocking-horse apples, and just as expensive.

I would strongly suggest that as the rifle has Sentimental family value, and as a virtually unused Remington product, it is worth doing some cleaning to it, and then getting the ammo it was made for; This all could be done for less than $100 dollars intiially;

The 8mm Lebel cartridge although it had design peculiarities, being derived from a larger Black Powder cartridge in 1886,was the world's first Smokeless cartridge, and can be reloaded to give reasonable to good results, for both Target shooting and Hunting.

I reload original Military cases (Berdan twin-flashhole primers) with original "Balle N" ( 230 grain lead core FMJBT) for my target shooting ( out of an RAC M07/15) as well as a French made M07/15M16 (5 round clip mag), and an original M1886 Lebel Tube loader.

The cases and projectiles come from "Pulling down" lots of defective Hotchkiss-stripped MG 8mm Lebel ammo (Primers dead), and re-using the funtioning componenets(Cases, Bullets and sometimes, the Powder)
I also have a Turkish converted Berthier M07/15 Forestry carbine, which I use for Pig shooting, also in 8mm Lebel (3-shot); for this I use Cast lead 220 grain round nose Proj. which drop pigs neatly up to 100 metres range.( again with Military cases.)

The 8x51R Lebel cartridge is much underrated, due to its case architecture; but the French used it in Two World Wars and numerous colonial "actions" to great effect, untill by the 1920s, its design failings led to its being partially replaced by a rimless cartridge; but it soldiered on to the mid to late 1960s, as a Police and MG cartridge in most of the French ex-Colonies, and of all the contradictions, whilst US Doughboys were armed with 8mm Lebel rifles and MGs in WW I (the Negro Regiments, and some of the US Infantry divisions), they then faced the VC armed with ex-French 8mm Lebel Rifles and MGs in the Vietnam War, some 55-60 years later.

Regards,
and send some Photos of the rifle, please.

Doc AV
AV Ballistics.