the first 2 inches of rifling is gone. How bad will that affect basic accuracy?
Counterboring (the 1/4" you mention) was a common re-arsenal practice, done to restore accuracy - due to damaged barrel crown. But, not sure what you mean by "the first 2 inches." Do you mean at the breech end (throat) or the barrel end?
Regardless, shoot it to test for accuracy - the target will tell. Most military rifles of the day were expected to hold about 3" @ 100 yds. with issue ammo.