I'm sure the rifle will shoot 1" at 100yds. I was basing my post on a 400 grain bullet that you had mentioned. A 250 grain bullet will make a huge difference in trajectory. The other reason I assumed the heavier bullet was you mentioned topping the gun with a Weaver 2.5X scope. A bit low on magnification for shooting 400 yards IMO.
Touche, yes with the 400s I'd limit this guy to 200yds, especially with cast bullets. The 2.5x isn't much hindrance to me. I can accurately (8" plate) hit it @ 400yds with my leupold 2.5x. It takes practice for sure.
Adam