3in., four shot groups at 100yds. with open sights using an old Remington semi-auto, and factory ammo- not too shabby. Nope, not bad at all!
Nothing wrong with Winchester 150gr. for deer hunting either. It'll do.
As noted, if you can convince your grandpa to go with a low end fixed power scope, say 4x, or maybe evena low magnification variable like a
1-4x, your groups will likely tighten up quite a bit.
Another alternative is to mount a Williams receiver peep sight. Much quicker, and generally more accurate to use than the standard open sights. Get it with the larger opening-twighlight aparture. Less expensive than most good scopes, too.
Source: Williams Gun Sight Co.
Link:
http://www.williamsgunsight.com/