Just got through sorting a few hunnert .45ACP by headstamp. I wanna see just how tight I can get those groups.

I found that Federal, Speer, CCI and Blazer all have much larger flash holes than other headstamps. My mag visor could reveal no differences whatsoever in the other characteristics. All the contours & dimensions of the rim looked identical. They are so much alike I just went ahead & tossed 'em all in the same box.

I'm guessing all four have their cases made by the same company?

I would think flash hole size would have quite an effect on combustion and would therefore be standardized? Or am I overthinking this?

To throw a wrench in the works I also found 2 Federal cases with "normal" sized flash holes...

Any thoughts?

I am not sure that reasonable variations in flash hole sizes have much affect on handgun cartridge performance. Frankly, I have never paid any attention to flash hole size and I religiously sort cases. What I am attempting to do is have cases that are consistent in internal capacity, wall thickness, and that will give consistent crimp and bullet pull. To do this I sort by manufacturer and again if some are nickel plated. This usually eliminates any variations that cause a hang up in the reloading process. Whenever possible I start with new unfired cases and I never use range brass that I know nothing about.

I will be interested in others' views about the importance of flash hole diameter in handgun ammo. Benchrest shooters will have an entirely different view of the importance of flash hole consistency!