CQB45ACP
Member
I guess you’re saying using all the same size flash holes in 9mm will produce greater consistency among two or more cartridges? I get your point (but have still seen no data) and don’t know that it’s helpful in the real world to do so unless we’re into some precision bench rest stuff.You don't have to but if you want greater "consistency", I would.
Same for checking finished OAL and chambered OAL for bullets setback. Many don't check it and wonder why their group sizes are not consistent.
But that doesn’t at all equate to one should drill out small 9mm flash holes.
The answer to OP’s original question—have we seen different sizes of flash holes in 9mm is—yes, ammo manufacturer’s use various sizes. We know at least two sizes, but beyond that who knows? In 45ACP it’s more than two.
Why? We do not know. Is it a problem? Not as far as any of us know. Do we need to drill out or throw out the small ones? Not as far as any of us know.