Some manufacturer's include two different expansion balls for tailering your ammo. My Lee die set has both .308" and .311" balls.
It may not grip the rifling as well and accuracy can go down, but you won't try till you've shot them. I have a Walther P1 that I shot with .356" sized bullets for years. When I finally slugged my P1's barrel, I was surprised to find that the bore diameter was .357".
Test loads with .357" and .358" sized bullets showed it shot more poorly with larger bullets.
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