At an indoor range awhile back a guy was shooting has 308 super high dollar rifle and everyone marveled at its beauty. I pulled out the old 1943 M44 Mosin Nagant with light ball ammo. Pulled the trigger once and guys came over to see, "what the hell was that!" It was a lot more fun to shoot than 7mm magnum or 30-06. Never shot a 308 though so can't compare.
Congrats on the Mosin nagant (whacha get,91/30 m38 m44?) I have a 91/30 and a M44 carbine.
I 'd say it's comparable to the .308 If you go with NEW ammo.Alot of the milsurp ammo tends to be mass produced in factories where quality control is a little lax,and since they didn't want Igor and Alexi shooting duds they tended to add a pinch of powder extra which can make for a little extra umph(and a realy cool muzzle flash)
Watch out for laquered steel casings as they can leave residue in the chamber causing "sticky bolt syndrome" and most milsurp ammo is VERY corrosive so be sure to clean the chamber and bore ASAP!!
I know I'm adding to this even while it was first posted in early 2009.
I too love the Mosin. I have a cherry M44 that the Romanian's built in 1955. I got it for 100.oo smacks and it was in my eyes worth 200.oo. The stock on mine is likely from a Beech tree I would guess and it is the nicest stock I have ever had in my dirty little hands. I bought mine on a used rack at the back of William's Gun Store in Davison, MI. A few years ago they would have 10-12 on sale at a time. Now it's 1-2 and I would pass them up because they look like they spent every day in the trench and never saw a cleaning rod or oil rag in their long lives.
My research is much like many other folks have told you early in this topic. It is a nice close match up with the 308 and in my book that takes care of any American big game. I wouldn't want to pick a fight with anything bigger than a Black Bear but you could and if you did your part and used the right ammo and placed your five shots well the bigger bear would die before he had hold of your leg and began making lunch out of you. That said don't begin the hunting adventure at 15 yards cause that is too late even with a 308. I wish you good times of large flames from the muzzle and lots of venison in your deep freezer. The gun is a wonderful, Ugly Betty that I have fallen for and find myself thinking I like better than a thousand dollar rifle next to it in the gun safe. If you like a scout set up the S&K mount is had for about 80.oo bucks but worth every cent. A bunch of cheap ones are out there but you get what you pay for and I like a mount with a heavy duty look, feel and application. Another 100.oo bucks gets you a nice pistol type long eye relief type scope that finishes the scout set up. Jeff Cooper had many articles he wrote and you could dig some up and get an idea of his professional ideas of such a gun and scout build of it. You could also have a good gun smith get envolved and drill + tap for a 3x9x40 that would take care of game +200 yards like a wonderful song.
I have talked long and my throat is horse....lol and good shooting the Mosin.