Flash holes, big vs little, any current evidence on the big ones?

It's been a long while since I heard any concern, griping, real evidence about the big flash holes in 45 brass.

Has that concern gone away?
Was it just a passing gripe?
Any real evidence one way or the other?

For Bullseye loads? No significant impact. Just don’t mix them with other cases.

Granted the big holes work.  But why not mix them?  How different a result do they give if mixed?

I had no idea what this discussion was about, so I looked around, and found this:
https://scholarsmine.mst.edu/cgi/viewcontent.cgi?article=8415&context=masters_theses

In practical terms, is the flash hole size and location a standard, that "everyone" follows, or is different ammunition sold with different flash hole sizes?  It sounds like this may be a non-existent concern for 99.99% of us, hopefully myself included.  Is it something some shooters can do to modify cases?  

For 45 ammo, since it is available with small and large pistol primers, does the flash hole size vary based on which primer is being used?

Since accuracy does seem to depend on the flash hole size, why wouldn't newly purchased ammunition automatically come with the optimum size flash hole for shooting accuracy?

I never worried about the size of the flash hole.  I do de-bur the flash hole just a carry over from loading rifle ammo.  Logic tells me that if the flash hole has been de-burred you will get a more even ignition and possibly a more accurate load.  We do tend to pole vault over mouse turds sometimes.

There were a few lots of (Winchester?) brass that had very large flash holes. If you have some, I’d keep them segregated. But other than that treat them the same.

THE LARGE FLASH HOLES WERE DESIGNED TO AID IN IGNITION OF POWDER WHEN USING  LEAD FREE PRIMERS. JP

Better way to ask my question in the first place

Based on experience or evidence....

Do large flash holes by themselves shoot any better or worse than regular small flash holes?

If you shoot mixed small and large flash holes together, do your groups suck?



I seem to have accumulated a quantity of Federal large hole brass.  I am trying to find out to keep it or recycle it.  I have plenty of good regular brass.  But no time to experiment.

A friend of mine has tested a lot of the brass variables, flash hole size included, and while there appears to be a measurable difference in accuracy, there does appear to be a very small, but statistically significant difference in velocity. 

How that relates to you and your loads, I can't say. What's your load, and I can ask my buddy- but only if it is BE or WST... I don't think she has tested any other powders in this scenario, FWIW.

I DID TEST WINCHESTER LARGE FLASH HOLE VS SMALL A FEW YEARS BACK. I ONLY TESTED WITH LEAD. AT 50 YDS FROM THE RANSOM IT WAS TOO CLOSE TO CALL. I DO SEPARATE THEM WHEN FOUND. PROBABLY ONLY DUE TO MY UN-DIAGNOSED OCD. JP

There are a couple past threads that both reference the same list of case preparation tests done that include the mention of flash hole deburring as being something to avoid.  I know deburring and size differences aren't quite the same, but deburring was mentioned earlier in this thread and if anyone is interested in reviewing those other threads, here they are so readers don't have to search:

brass variation

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