Flash hole size

cdoc42 · January 23, 2013, 12:57 AM

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?

Magnum Wheel Man · January 23, 2013, 10:21 AM

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

243winxb · January 23, 2013, 10:24 AM

http://www.thehighroad.org/showthread.php?t=664708 See post #4, "lead-free" handgun ammo has a large one.

Brian Pfleuger · January 23, 2013, 10:52 AM

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.

**Unclenick** · January 23, 2013, 11:25 AM

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.

F. Guffey · January 23, 2013, 03:38 PM

“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?’

F. Guffey

cdoc42 · January 23, 2013, 06:56 PM

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 temps.....it may not be until April....how do you folks in Minnesota do it?

rclark · January 23, 2013, 07:31 PM

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.

January 23, 2013, 12:57 AM	#1
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	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?

January 23, 2013, 10:21 AM	#2
Magnum Wheel Man Senior Member Join Date: July 26, 2006 Location: Southern Minnesota Posts: 9,333	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 __________________ In life you either make dust or eat dust...

January 23, 2013, 10:24 AM	#3
243winxb Senior Member Join Date: July 26, 2011 Location: USA Posts: 1,730	Primer flash hole sizes-3-or more? http://www.thehighroad.org/showthread.php?t=664708 See post #4, "lead-free" handgun ammo has a large one.

January 23, 2013, 07:31 PM	#8
rclark Senior Member Join Date: February 12, 2009 Location: Butte, MT Posts: 2,622	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. __________________ A clinger and deplorable, MAGA, and life NRA member. When guns are outlawed, only outlaws will have guns. Single Action .45 Colt (Sometimes colloquially referred to by its alias as the .45 'Long' Colt or .45LC). Don't leave home without it. That said, the .44Spec is right up their too... but the .45 Colt is still the king.

January 23, 2013, 10:52 AM	#4
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	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. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

January 23, 2013, 11:25 AM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	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. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

January 23, 2013, 03:38 PM	#6
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	“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?’ F. Guffey

January 23, 2013, 06:56 PM	#7
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	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 temps.....it may not be until April....how do you folks in Minnesota do it?