To a certain degree, it depends on caliber and the intended use. For the larger bores, I expect them to shoot into 1.5" at 50 yards with a load that gives reasonably close to standard velocity (as adjusted for barrel length). If it won't do that, I have it re-regulated. If that didn't work, I'd sell it and try again. I've never had to sell one.

When a scope is added to a rifle that was regulated without one, groups with the scope are often larger than with the sights. The weight of the scope on top of the barrels dampens the recoil arc during barrel time. Some rifles are more forgiving about this than others.
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