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Old November 16, 2012, 07:22 PM   #1
SEHunter
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Flash Hole Size-Whats too large/small?

Opologize for this subject that has been discussed so much before...

I understand that .080 is the US standard but what im not sure of is how large is too large? I have some Winchester brass in 22-250 that has some crazy flash hole sizes, or atleast inconsistant with eachother. This was store bought Super-X ammo i have shot and am preparing for reloading.

Im not a BR shooter but this is a varmint rifle and i am loading for as much accuracy as possible. Is there an understood tolerance used by the majority (who care about the different flash hole sizes)? All my drill bits are standard sizes to the nearest 64th of an inch. What size do i need to use as a nogo?

Thanks.
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Old November 16, 2012, 10:57 PM   #2
res45
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The SAAMI spec. for rifle cases using the large primer is 0.078" - 0.082"

Small primer pocket rifle and pistol cases use a smaller flash hole size of .074" - .078"

European CIP brass use 1.6mm - 1.7mm flash holes.
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Old November 17, 2012, 12:07 AM   #3
SEHunter
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so based off that, people scrap any cases that measure over .082 ?
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Old November 17, 2012, 01:00 AM   #4
Creeper
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Quote:
Im not a BR shooter but this is a varmint rifle and i am loading for as much accuracy as possible.
If that's the case, I'd suggest you toss the Winchester brass and get 100 pieces of Lapua brass... it's the best there is and can typically be reloaded 3-5 times more than lower grade brass.
In a 200 count, raw lot, the total deviation was less than 2.0 grains. Flash holes are .078" with no measureable deviation. Case length variation was less than .003".

Yeah... it's around a buck a case, but IMO, well worth it if what you say is true.
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Old November 17, 2012, 08:36 AM   #5
SEHunter
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That may be in the cards. Whats worse is that before i bought the loaded ammo, i was looking through the bag of some Win unprimed virgin brass and literally about 1 out of every 4 cases had a flash hole that was like smeared- it looked like the machine began to punch it out off center then it slid its way over to the center. They appeared to be larger because of it,

I heard Lapua is better than Norma even though i used to think they were made by the same company. Aside from the facts you posted above, is there any other descriptions that Lapua is know for?- Like has it been determined where in the mix they usually fall in case capicity when compared to same cartridge of other brands??
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Old November 17, 2012, 10:35 AM   #6
F. Guffey
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The flash hole: A reloader walks up to a case, turns it over and then measures the flash hole, the diameter of the flash hole is .085”, then what? A conclusion is dawned by the reloader? That is not possible, because, the reolader did not know the diameter of the flash hole when the case was manufactured, back to measuring before and again after. A reloader fired one 308 Winchester case 47 times, I ask him the weight of the case before he started, he did not know (the weight) and he did not know why I ask the question, I did not get around to asking him the diameter of the flash hole through 47 firings, I did not ask him the diameter of the case head before and again after the test? I did not ask him the case head thickness before and again after he started his test.

I do not measure the diameter of the flash hole for the sake of knowing the diameter of the flash hole, but when I do measure the flash hole expect the diameter of the flash hole to increase in diameter the next time it is fired. One member on this forum drills his flash holes to a uniform diameter, first reason: JIC, just in case it matters. then there is the effect pressure has on the case when fired. Always the primer, get ‘tuffer’ primers, I read that a lot, if pressure has an effect on a case every part of the case is effected starting with the flash hole, I have cases with flash holes that were rendered scrap in one firing, the rendering to scrap was not confined to the flash hole, the head of the cases were crushed, the diameter of the primer pocket would not hold a shot gun primer, the case head thickness decreased, the primer? The first sign of an indication there was/is a problem with pressure? I did not find them until I took the rifles apart, sure enough, the primer showed signs of pressure. I was told the receivers were suspect. seems the receivers started out as 7MM57s and were converted to 30/06, the 30/06 barrels were shot out and one still the case in the chamber less the case head. the suggestion was to use the barrels as tomato stakes??? I purchased 4 rifles for $25.00 each, that means nothing to the tomato ‘stake-rs’ but for me? I cut the chamber off of the barrel and make ‘instant’ chamber gages, real chamber gages, not the chamber gages sold on the Internet that are poor copies of the L.E. Wilson case gage.

I got a deal on LC MATCH 30/06 cases, .08 cents each, the flash holes were not in the center, I thought I had purchased a life time supply, not so, seems I was supposed to call friends and ask if they wanted a few, I called Pat in Ohio, he made me a deal on on more cases plus shipping (very reasonable), I ordered another 4,000 cases. When it comes to case forming there is nothing like starting with a new unfired case, and, the ideal a case will not cost me more than .08 cents each plus my time.

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Old November 17, 2012, 10:49 AM   #7
F. Guffey
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Forgive, there is .015625 difference between drill diameters when the set is in 1/64th. Back to keeping up with the diameter of the flash hole, If I fired a case and the diameter increased .015” I would determine what went wrong, back to the first part, if the flash hole increased in diameter .015” other signs of pressure would be obvious.

A letter and or number set would be a better choice, harbor Freight, then there is the big box of drills, $120.00 plus.

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Old November 17, 2012, 11:08 AM   #8
243winxb
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There are 2 or 3 different sizes of flash holes. I use this for the 243. Opens the hole to the correct size and puts a bevel on the inside.
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Old November 17, 2012, 09:15 PM   #9
SEHunter
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Thanks for the info guys. I have discarded a few cases but the majority passed the bit test.
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Old November 18, 2012, 07:42 AM   #10
Bart B.
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Get a couple of drill bits to use as hole or "pin" gauges. A #45 is .0820" and a 5/64" is .078125".

If the #45 won't go into the flash hole but a 5/64" will, they're good for tolerance. If the 5/64" won't go in the hole's too small for specs. Conversley, if the #45 does go in, the hole's too big for specs.

I've made 20-shot test groups comparing factory flash holes that varied about .003" in that range to cases that had them all drilled out to .086" with a #44 drill bit. No difference in accuracy whatsoever.

Therefore, I don't think one needs "exact" flash hole diameters. It's my opinion that anything over .086" will start causing high pressure problems; the powder's going to ignite faster and the peak pressure may well be higher.
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Old November 18, 2012, 07:53 AM   #11
Bart B.
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Guffey comments on my .308 Win. case I reloaded 47 times:
Quote:
A reloader fired one 308 Winchester case 47 times, I ask him the weight of the case before he started, he did not know (the weight) and he did not know why I ask the question, I did not get around to asking him the diameter of the flash hole through 47 firings, I did not ask him the diameter of the case head before and again after the test? I did not ask him the case head thickness before and again after he started his test.
I didn't care what any dimension the case was before, during or after that test except for case length. Nor did it matter to me why he asked about it. I knew it didn't make any difference as far as accuracy is concerned. Others have done the same and they didn't care either and got the same accuracy for the life of the case. The primer pocket in my case didn't open up enough to make any noticable difference in force needed to seat the primers.

Some folks reloading the same case a few to several dozen times notice the primer pocket getting too big to hold new primers. So they swage the case head back down a couple thousandths and start over with a tight primer pocket. The flash hole diameter probably gets a bit smaller, too.

Last edited by Bart B.; November 18, 2012 at 10:47 AM.
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Old November 18, 2012, 09:31 AM   #12
SEHunter
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BartB, thanks. That was exactly what i was looking for.
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