Flash hole enlargement...

**Shane Tuttle** · October 22, 2007, 07:20 PM

Just wanted to run this by you guys and gals...

I've been curious to know if there's any ramifications or benefits to enlarging flash holes. My thoughts were:

1. Hey, slight enlargement the flash hole, powder will be better exposed to the primer ignition. This will provide better burn rates.

2. What, are you stupid? Case manufacturers have studied this over and over. The size is just right and any bigger will impede structural rigidity for primers.

My quiery is for pistol and rifle alike...especially rifle.

Trapper L · October 22, 2007, 07:53 PM

If you run into any of the Winchester brass marked NT in 45ACP, it will probably have a flash hole that looks almost twice the size of a normal one. I called the guys at Winchester as I was sent a several thousands rounds of the brass for loading and I just knew there was a major mistake. Turns out the larger flash hole is for the primers that have no lead in the priming mixture. They said to load it as normal. I did and the point of impact did not change for the weapons I was loading for. Generally, I don't worry about flash holes on hunting loads. For bench ammo, I will deburr the flash hole inside and out and make sure it is .081 in diameter and perfectly centered and round. All others are dropped down to hunting brass. I played with flash hole sizes with a .261x 47 years ago and it didn't make any difference as to how big, just as long as it was consistant in size. But I also know a guy that had the habit of making his flash holes larger. He claimed better ignition. He quit when he got a round stuck in the chamber and used a rod down the barrel and a hammer to attempt to force extract the round. It went off. He lost three fingers. He also won't use a ball powder anymore- says it's too dangerous. And this guy is still a top notch gunsmith.

**Shane Tuttle** · October 22, 2007, 09:14 PM

Hmmmmmm...how did I know I could count on you to chime in, Trapper?

Scorch · October 22, 2007, 10:18 PM

The size of the flash hole controls how far into the powder column the flame goes. There is a balance between large hole/short, wide flame and small hole/long, skinny flame. I have read that benchresters actually use a reamer or drill to make them the perfect size, about .040". But you don't want them very much bigger than they already are.

Red_Eagle · October 23, 2007, 04:56 AM

I had to drill out some flash hole the other night. It was once fired Igman 308 winchester. Appearantly they use smaller flash holes in Bosnia than we do here.

MADISON · October 23, 2007, 07:20 AM

I don't know if it actually improves accuraacy but, I use the LYMAN "universal" primer hole uniformer on all my rifle brass. It only takes a few seconds...

Jim Watson · October 23, 2007, 07:21 AM

Benchrest shooters tend toward smaller flash holes even to the point of turning down decapping pins. I wouldn't mess with them except to deburr. As said, uniformity counts.

Trapper L · October 23, 2007, 11:21 AM

Scorch, curiousity question, who is making brass with flash holes that small? Lapua makes smaller ones but they are .059. You have to get special decapping pins as the normal ones are .0625 but I've never heard of any flash holes that small-.040. Decapping pins must be an issue. They would have to be something like .035-.037 and it would seem that they would be fragile for the work they do. Is there an issue with decapping pins piercing the primers? That's an extremely small pin pushing the primer out. It would seem that the pin is going to be more apt to go thru the primer rather than push it out. Just curious, I've never heard of any flash holes that small before.

brickeyee · October 23, 2007, 01:31 PM

Larger flash holes run the chance of having powder migrate down into the primer.
It is a balance between allowing enough flame into the powder volume and keeping the powder out of the primer.
Uniform is generally more important than absolute size.
PPC cases have a relatively small flash hole, but just about any BR shooter 'uniforms' them and they are cut slightly larger.
Sinclair International has all sorts of ‘uniformers’.
Most brass (Norma being the major exception in some calibers) has punched holes. Thus typically leaves a bur inside the case. The uniformer removes the bur, cuts an even chamfer, and makes all the holes the same size.
Most measure from the case mouth for depth so cases must be the same length.

grymster2007 · October 23, 2007, 01:37 PM

So where might one find flash hole diameters for various cartridges?

Just here I'm seeing .059, .040, .0625.

Are they determined by by caliber or rifle/handgun or brass manufacturer?

Trapper L · October 23, 2007, 03:35 PM

Quote:

Larger flash holes run the chance of having powder migrate down into the primer.

Apparently not an issue. Winchester folks don't have issues with large primer flash holes and have you ever loaded H110 powder? H110 will run thru a flash hole faster than you can catch it. Same with most ball powders.

Quote:

So where might one find flash hole diameters for various cartridges?

Just here I'm seeing .059, .040, .0625.

Flash holes in most US arms will be actually punched to .080. Some will be a hair larger depending on the maker and the equipment. Lapua has the BR series of brass that comes with a smaller flash hole that is .059. Some of the older Remington match brass also had smaller flash holes. The .0625 is the size of a standard decapping pin in your sizing die for a small rifle/pistol. Large primer pins will be .070 because of the larger bearing surface of the primer and they are a little harder to remove. The larger pin limits primer piercing.

I'll see if I have any of the NT brass with the large flash hole. If I can find some, I'll post a pic showing the almost double sized flash hole. Like I said, it made no difference in the point of impact or accuracy of the ammo I loaded.

brickeyee · October 23, 2007, 03:39 PM

"Like I said, it made no difference in the point of impact or accuracy of the ammo I loaded."

Did you have a gun accurate enough to tell? Like a BR rifle?

1goodshot · October 23, 2007, 05:54 PM

I read somewhere that blanks use a larger flashhole.

**Shane Tuttle** · October 23, 2007, 09:44 PM

Quote:

I have read that benchresters actually use a reamer or drill to make them the perfect size, about .040".

Perhaps you meant using a #40 drill bit? That equates to 2.50mm or .0980" or thereabouts...

Quote:

Benchrest shooters tend toward smaller flash holes even to the point of turning down decapping pins.

Do you know why? Just the trend these days? Maybe the longer, slender flame that it produces as Scorch stated?

Quote:

The size of the flash hole controls how far into the powder column the flame goes.

I'm trying to picture if this would be the case on a compressed load. Any thoughts?

October 22, 2007, 07:20 PM	#1
Shane Tuttle Staff Join Date: November 28, 2005 Location: Montana Posts: 9,443	Flash hole enlargement... Just wanted to run this by you guys and gals... I've been curious to know if there's any ramifications or benefits to enlarging flash holes. My thoughts were: 1. Hey, slight enlargement the flash hole, powder will be better exposed to the primer ignition. This will provide better burn rates. 2. What, are you stupid? Case manufacturers have studied this over and over. The size is just right and any bigger will impede structural rigidity for primers. My quiery is for pistol and rifle alike...especially rifle. __________________ If it were up to me, the word "got" would be deleted from the English language. Posting and YOU: http://www.albinoblacksheep.com/flash/posting

October 22, 2007, 09:14 PM	#3
Shane Tuttle Staff Join Date: November 28, 2005 Location: Montana Posts: 9,443	Hmmmmmm...how did I know I could count on you to chime in, Trapper? __________________ If it were up to me, the word "got" would be deleted from the English language. Posting and YOU: http://www.albinoblacksheep.com/flash/posting

October 23, 2007, 07:20 AM	#6
MADISON Senior Member Join Date: January 1, 2000 Location: Roanoke, Virginia Posts: 2,678	Flash Hole Uniformer I don't know if it actually improves accuraacy but, I use the LYMAN "universal" primer hole uniformer on all my rifle brass. It only takes a few seconds...

October 23, 2007, 01:37 PM	#10
grymster2007 Senior Member Join Date: May 22, 2007 Location: In the oak studded hills near Napa Posts: 2,203	So where might one find flash hole diameters for various cartridges? Just here I'm seeing .059, .040, .0625. Are they determined by by caliber or rifle/handgun or brass manufacturer? __________________ grym

October 22, 2007, 07:53 PM	#2
Trapper L Senior Member Join Date: November 20, 2006 Location: South Texas Posts: 804	If you run into any of the Winchester brass marked NT in 45ACP, it will probably have a flash hole that looks almost twice the size of a normal one. I called the guys at Winchester as I was sent a several thousands rounds of the brass for loading and I just knew there was a major mistake. Turns out the larger flash hole is for the primers that have no lead in the priming mixture. They said to load it as normal. I did and the point of impact did not change for the weapons I was loading for. Generally, I don't worry about flash holes on hunting loads. For bench ammo, I will deburr the flash hole inside and out and make sure it is .081 in diameter and perfectly centered and round. All others are dropped down to hunting brass. I played with flash hole sizes with a .261x 47 years ago and it didn't make any difference as to how big, just as long as it was consistant in size. But I also know a guy that had the habit of making his flash holes larger. He claimed better ignition. He quit when he got a round stuck in the chamber and used a rod down the barrel and a hammer to attempt to force extract the round. It went off. He lost three fingers. He also won't use a ball powder anymore- says it's too dangerous. And this guy is still a top notch gunsmith.

October 22, 2007, 10:18 PM	#4
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	The size of the flash hole controls how far into the powder column the flame goes. There is a balance between large hole/short, wide flame and small hole/long, skinny flame. I have read that benchresters actually use a reamer or drill to make them the perfect size, about .040". But you don't want them very much bigger than they already are. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

October 23, 2007, 04:56 AM	#5
Red_Eagle Senior Member Join Date: February 3, 2007 Location: Western NY Posts: 598	I had to drill out some flash hole the other night. It was once fired Igman 308 winchester. Appearantly they use smaller flash holes in Bosnia than we do here.

October 23, 2007, 07:21 AM	#7
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,535	Benchrest shooters tend toward smaller flash holes even to the point of turning down decapping pins. I wouldn't mess with them except to deburr. As said, uniformity counts.

October 23, 2007, 11:21 AM	#8
Trapper L Senior Member Join Date: November 20, 2006 Location: South Texas Posts: 804	Scorch, curiousity question, who is making brass with flash holes that small? Lapua makes smaller ones but they are .059. You have to get special decapping pins as the normal ones are .0625 but I've never heard of any flash holes that small-.040. Decapping pins must be an issue. They would have to be something like .035-.037 and it would seem that they would be fragile for the work they do. Is there an issue with decapping pins piercing the primers? That's an extremely small pin pushing the primer out. It would seem that the pin is going to be more apt to go thru the primer rather than push it out. Just curious, I've never heard of any flash holes that small before.

October 23, 2007, 01:31 PM	#9
brickeyee Senior Member Join Date: December 29, 2004 Posts: 3,351	Larger flash holes run the chance of having powder migrate down into the primer. It is a balance between allowing enough flame into the powder volume and keeping the powder out of the primer. Uniform is generally more important than absolute size. PPC cases have a relatively small flash hole, but just about any BR shooter 'uniforms' them and they are cut slightly larger. Sinclair International has all sorts of ‘uniformers’. Most brass (Norma being the major exception in some calibers) has punched holes. Thus typically leaves a bur inside the case. The uniformer removes the bur, cuts an even chamfer, and makes all the holes the same size. Most measure from the case mouth for depth so cases must be the same length.

October 23, 2007, 03:39 PM	#12
brickeyee Senior Member Join Date: December 29, 2004 Posts: 3,351	"Like I said, it made no difference in the point of impact or accuracy of the ammo I loaded." Did you have a gun accurate enough to tell? Like a BR rifle?

October 23, 2007, 05:54 PM	#13
1goodshot Senior Member Join Date: November 11, 2001 Location: chandler,az Posts: 929	I read somewhere that blanks use a larger flashhole.