Unfortunately with factory cartridges your rifle will be illegal in Scotland as it is too slow. In England and Wales you have only the muzzle energy to bother about. This from accurate reloading website forum posted by me: This from the RWS website:
6.5 x 54 Mann.Sch. Bullet: TMR 10.3 g
Muzzle Velocity V[m/s]: 670 m/s
Muzzle Energy E[J]: 2312 joules
BC value: 0.315 Test barrel length: 450 mm
So the Deer Act specifies 2,305 joules muzzle energy. It seems to me that this RWS load, in a 450mm (SEVENTEEN INCHES) barrel just makes it.
Most M-S rifles are what? 20" plus? I can't remember what it was on the 1903 Model I had I think 23.50"?
If you've got one of those stupid silly carbines with a sub 18" barrel and a full length stock. Hmm! That may be a problem. But still OK if RWS are correct in their figures.
You should be OK as far as I read it. 10.3 grams is effectively 159 grains.
Go RWS!
http://www.rws-munition.de/en/...ic_data.htm?navid=10
Now whilst it might be legal does it make sense?
It is, in fact, a superb deer cartridge EVEN on the hill. A lot of the old time rifles swore by its 160 grain bullet as you could hear if it gave a good hit t the beast by the "thwack" it made when it finally arrived on the target!
But! These rifles are notorious for headspace problems and I would not buy one unless I had fired it first to check that. Also most date from the period of mercuric primers and cordite. So again, being already "large" in the bore, any wear to the bore is a greater problem than in a rifle with a "tight" bore.
Twist may, or may not, be a consideration. I think but may be wrong, that some had a gain twist. Certainly I had a Mannlicher 1903 about thirty years ago but can't remember if it was or was not a gain twist.
Accuracy? Again don't expect better than 3 moa. If you get 2 moa you've been very, very, lucky!
What is the 'scope, what are the mounts, how much is the package or is it a gift? Ammunition, btw, will be hideously expensive! When I bought factory RWS 6.5 x 54 in the late 1970s it was £60 per 100 then!