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Old January 23, 2013, 12:57 AM   #1
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Flash hole size

I'm resizing .45 ACP's tonight and just happened to notice what looked like a large flash hole in a "once fired" Winchester case. It easily accepted a 1/8" drill bit. A new unfired Starline case passed a 5/64" but not 3/32."

So I began paying closer attention. 8 Winchester cases all passed a 1/8" bit. 16 Federal and 5 Speer cases passed a 3/32 bit.

A "top brass" case only passed a 1/16" bit!!!

It has been my understanding during the years I've loaded rifle that a uniform flash hole in a rifle case should be 5/64."

I'm assuming the 1/8" holes are too large and these are certainly not "once fired." Since I've reloaded several hundred rounds up to this point before I noticed this apparent discrepancy, is there any danger to having too large a flash hole in the primer pocket?
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Old January 23, 2013, 10:21 AM   #2
Magnum Wheel Man
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1/8" hole is quite large... you could always use them for wax bullets...

or possibly low weight bullets, with light charges... I would not mix them in with your regular reloads though
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Old January 23, 2013, 10:24 AM   #3
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Primer flash hole sizes-3-or more? See post #4, "lead-free" handgun ammo has a large one.
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Old January 23, 2013, 10:52 AM   #4
Brian Pfleuger
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Load 'em and shoot 'em. I guarantee that the vast majority of loaders pay no attention to the size of flash holes. If it was dangerous under ordinary circumstances, they wouldn't do it.
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Old January 23, 2013, 11:25 AM   #5
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All the above. If you look at the case it will liekly have the letters "NT" on it, for "Non-toxic". It means the primer used DDNT instead of lead styphnate, which is a more violent explosive and if the hole isn't made bigger it backs itself out of the pocket an can pop itself before the case is pushed back over it to surround and protect it.

The standard primer flash hole is 0.080"±0.010", so, 0.070" to 0.090". That means a #50 drill should fit through, if snuggly, while a #42 drill bit should not fit. 5/64" is about 0.0781", so slightly smaller than average. Keep in mind that when you mic standard drill bits it's not uncommon for them to be a couple or three thousandths under their nominal size. There's a table of drill sizes, here.

The 1/8" hole is, as already explained, used for NT, for wax bullet shooting, and is also used by the military for their G11 formulation high temperature primers. I've never heard of a .45 Auto case having a problem with the substitution of a standard primer in these. It's a low pressure round anyway.
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Old January 23, 2013, 03:38 PM   #6
F. Guffey
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“I'm assuming the 1/8" holes are too large and these are certainly not "once fired." “

Not sure about my quote of a quote but... 1/8” or .125”, depends on how the flash hole got to be .125”, I have almost given up on measure before and again after, does not seem reloaders/shooters are interested in where they started, most fire first then measure. For that reason if you do not know the diameter of the flash hole before firing little information can be gained by measuring after firing. BUT! if the flash hole is ..070” in a new case before firing and .125” after firing you will understand why I say the beginning signs of excessive pressure starts from the inside of the case with the flash hole, primer pocket and crushed case head. Again, WHO MEASURES?

I have shell holders that fit, my favorite shell holders are the ones that fit only where they touch, loose shell holders have versatility.

Shell holders that fit cause reloaders to ask, ‘What is wrong with this 40 year old shell holder?’

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Old January 23, 2013, 06:56 PM   #7
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Thanks to all. I must say after 37 years of reloading the most attention I've ever paid to flash holes was to see if one was there, but the 1/8" holes really got my attention. They were all Winchester cases and I didn't find any "NT" on them, even when magnified. My 5/64 drill bit measures 0.78". Well, I'll fire a few as soon as we get above these freezing may not be until do you folks in Minnesota do it?
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Old January 23, 2013, 07:31 PM   #8
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I might be the exception, but I remember firing a few with the bigger flash hole and had punctured primers (a pin hole). Threw them out after that. This was in my Ruger .45 Convertible. Bigger flash holes and small primer pockets in .45ACP cases are prime candidates for the round file (or wax bullets) as far as I am concerned.
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