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flash holes in brass #16431648 09/13/21
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Hello all.
I have been thinking about making all of the flash holes in my .223 brass the same size. The reason is just to simply get the same amount of primer flash into the powder, every time. I have been measuring the holes with my numbered drill bit set. It seems that most of the brass has a hole larger than .078 but smaller than .086" in diameter. There are occasional variations to this but most of the holes fall in between these 2 numbers. Has anyone drilled out the flash holes in order to get uniform ignition in .223 and if so what did you settle on ??

I'm finding that very little brass is being removed with #45 drill bit (.082) and more brass is being removed with the #44 bit (.086) in most of the holes. One glaring exception is Aguilar brass and the #44 fall right through without touching a side. And the Winchester 5.56 brass the #45 bit goes right through but the #44 takes just a bit off. Has anyone done this before ??

kwg


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Re: flash holes in brass [Re: kwg020] #16431655 09/13/21
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I use a Lyman flashhole uniforming tool. It probably makes zero difference in the real world, but when the winters get long reloading OCD kicks in.


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Re: flash holes in brass [Re: kwg020] #16431725 09/13/21
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I used to use a #45 bit but just use my Lyman flash hole tool these days.


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Re: flash holes in brass [Re: kwg020] #16432088 09/13/21
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Me too…


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Re: flash holes in brass [Re: kwg020] #16432091 09/13/21
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I know, most of you guys aren't welders, but I've been using a torch tip cleaner of the appropriate size to clean/debur the flash holes in my brass. Works like a champ.. No need to drill it out. It is good, however, to make sure it doesn't have a burr and they are all roughly the same size. It will help with consistent ignition of the powder and also consistent accuracy..


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Re: flash holes in brass [Re: kwg020] #16432588 09/14/21
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Knew a guy who drilled out the flash holes for better ignition, well he got it. Froze the bolt on shot 2, busted the bolt handle off and I never saw that rifle again.

General reference, flash hole size should be .080, and K&M makes a 25 buck tool just for that.



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Re: flash holes in brass [Re: kwg020] #16433114 09/14/21
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I have simply chucked up my #45 into my drill press and go to town drilling out the holes. The #45 is .082" diameter and about 33% of the brass touches nothing going through. The other 66% takes off varying levels of carbon and brass. I'm going to drill out some holes using the .086 #44 and see if there are any pressure signs. I did find one entry in a google search that said the holes should be 2 millimetres large. That is .0787" diameter.

I can only tell you once I started this, the holes vary in size and there seems to be no consistency between different brass makers. Some are much larger than 2 mm and many are smaller. This can't help accuracy.

kwg


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Re: flash holes in brass [Re: kwg020] #16433178 09/14/21
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The more expensive brass they drill the hole. It’s more consistent than that which is punched. Hasbeen


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Re: flash holes in brass [Re: ruffcutt] #16433248 09/14/21
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Originally Posted by ruffcutt
I use a Lyman flashhole uniforming tool. It probably makes zero difference in the real world, but when the winters get long reloading OCD kicks in.


I use this tool also, doubt it makes any difference in the shooting I do, but it only takes a second.

Re: flash holes in brass [Re: kwg020] #16433351 09/14/21
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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.

Original spec on 6 PPC which we all know is the most inaccurate round out there is .0625

Seems that smaller is better.



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Re: flash holes in brass [Re: kwg020] #16433378 09/14/21
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Your post reminded me of this masters thesis I came across awhile back regarding flash hole size in .223 and .308 brass and the effects of flash hole offset and orientation on precision and pressure.
It really gets down into the rabbit hole but some may find it interesting.
Teaser - the 3mm flash hole seemed best. In other words, larger is better.

Effects of flash hole deviation


Abstract from above link

The objective of this research is to determine the effect of dimensional and
positional changes of the primer flash hole on the performance of factory-grade rifle
ammunition.

The studied variables were flash hole diameter, offset from center, and
orientation of the offset in the primer pocket.
Cartridge performance was quantified by measuring muzzle velocity, chamber pressure,
and target grouping size (precision).

Five different flash hole diameters were tested for both the Remington .223 and
Winchester .308 calibers: 1.4mm, 2.0mm (the Fiocchi standard), 2.4mm, 2.8mm, and
3.0mm. Each diameter was tested at three offsets: centered (no offset), 0.5mm from
center, and 1.0mm from center. Each of the 0.5mm and 1.0mm offsets were tested at
three orientations: up (12 O’clock), side (3 O’clock), and down (6 O’clock).

Every flash hole was manually drilled and each cartridge hand-loaded in order to conduct
controlled testing of the flash hole variations. Testing took place in two segments with the muzzle
velocity and precision measured at a private range outside Rolla, MO and chamber
pressure and a second muzzle velocity measured at Fiocchi of America (Ozark, MO).

Results showed that muzzle velocity and chamber pressure varied 1-4% from the
control flash hole as hole diameter, offset, and orientation changed. The precision,
particularly in the 3mm diameter and centered flash hole cases resulted in improvements
of up to 28%. Variations in flash hole diameter, offset, and orientation do affect cartridge
performance.


Alternate flash hole diameters exist that improve powder ignition
consistently as well as precision. Off centered flash holes increase target grouping size
and result in less consistent muzzle velocity and chamber pressure values.

Last edited by NVhntr; 09/14/21.

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Re: flash holes in brass [Re: kwg020] #16433529 09/14/21
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3 mm
That is huge. That equals just over 0.118". Thanks for the input NVhntr. That's interesting. I have drilled some at .082 with a #45 drill bit and some at .086 with a #44 bit. The .082 drill is 2.1 mm and the .086 is 2.2 mm. This is in .223 brass. As I said before nothing seems to be consistent when it comes to hole size. I'm sure most of them are close to the 2 mm I read about on another forum but I have also seen some that I would guess are approaching 2.5 mm. Since I am drilling in the existing holes I can't do much about off center holes.

kwg


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Re: flash holes in brass [Re: kwg020] #16435546 09/14/21
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And folks have been uniforming their brass for how long?


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Re: flash holes in brass [Re: kwg020] #16435567 09/14/21
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Interesting stuff, but hard to take much advantage of unless you are shooting a rifle capable of exceptional accuracy. Some of the best shooting factory ammo I’ve ran is the Fiocchi 223 with vmax bullets. Ih has some of the most inconsistent flash holes in terms of centered & size That I’ve ever seen but that stuff will shoot!

Re: flash holes in brass [Re: 1minute] #16437111 Yesterday at 12:56 PM
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1minute said:

[quote=1minute]And folks have been uniforming their brass for how long? [/quote



Today I went to the range with the primer hole drilled brass. The holes were drilled with a #44 bit to a diameter of .086". (2.2 mm's) I loaded 50 pieces of .223 brass of various makes with 24.6 grains of IMR 3031. I chose this powder because it is faster burning and develops more pressure at the chamber. As per the Winchester reloading site 24.6 grains of 3031 develops 52,500 lbs. of pressure at the chamber under a 55 grain bullet. 24.6 grains pretty much fills a .223 case. All loaded under a 55 grain Hornady full metal jacket bullet. I did add just a slight crimp to the cases with a Lee Factory case crimper. I shot from a bench with the rifles on sand bags at the front and the rear.

I chose 2 different primers. Winchester small rifle and Federal Match small rifle primers all loaded into the once fired brass. After firing the ammo I found that the Federal Match primers were flat with the base of the brass but with no punctures of the primer cup and no splash. Just flat. I saw no other signs of excess pressure on the rims of the cases and I had no split case necks or mouths. The Winchester primers were not as flat and still showed rounded edges. Here again no signs of excessive pressure on the base of the case, no primer splash and no split case necks or mouths.

I shot these out of 2 different rifles. A Mini 14 with iron sights and an AR with a fixed 10 power. All shot at 50 yards. The brass out of both rifles looked identical except for the color of the primers. There was no way to tell just by looking at the brass which piece came out of which rifle. The accuracy of the ammo that was loaded with the Federal Match primers shot out of the AR15 showed the best groups. Which I expected. I have too much astigmatism in my eyes to really call anything I shot out of the Mini 14 a group. I managed to keep them on a 4" target at 50 yards. That is as good as it gets for me. Besides, if I'm going to blow up a rifle I don't want to blow up an accurate one so the Mini went first.

The most unusual thing I did notice was where the brass landed. My Mini is notorious for throwing brass at least 20 feet and throwing it in different directions. This time the Mini pretty much piled the brass 20 feet from the bench in one spot. The brass left the rifle just a bit passed the 3:00 o'clock position and it all landed at the same distance in the same pile. This is a first. It's usually spread over about 3 counties and maybe a small city or two. The AR sent the brass 10 feet at the 4:00 o'clock position and into the same pile as well. It made it easy to find.

My conclusions are: drilling the primer hole to .086 and shooting fast burning powder you may see some signs of pressure at the higher ends of the loads. I know there are some varying factors like chamber dimensions and the like that could skew this. Do I see any reason to drill the primer holes any bigger than the .086 (2.2 mm) ?? Absolutely not. The primary reason for shooting the brass with the slightly bigger holes is to see if I could achieve improved accuracy while looking for signs of pressure. I don't see where the accuracy improved so much but finding that the brass pretty much ended up in the same location told me that the rate of burn inside the cases is now more consistent than reloading brass with varying primer hole dimensions.

Now that I determined that it appears to be safe I feel good about moving onto rifles that are more accurate and search for any improvements.

kwg








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Last edited by kwg020; Yesterday at 01:00 PM.

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Re: flash holes in brass [Re: kwg020] #16437931 Yesterday at 05:22 PM
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You piqued my interest. I have loads of LC brass I think I'll try this with. Maybe factory size for control, and then stepping up to 3mm as in the information above.
I want to see if that 28% accuracy improvement is obtainable. I'm not going to worry about offset flash holes, I'll just use brass with centered holes.


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Re: flash holes in brass [Re: NVhntr] #16438135 Yesterday at 06:17 PM
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Originally Posted by NVhntr
You piqued my interest. I have loads of LC brass I think I'll try this with. Maybe factory size for control, and then stepping up to 3mm as in the information above.
I want to see if that 28% accuracy improvement is obtainable. I'm not going to worry about offset flash holes, I'll just use brass with centered holes.

That sounds interesting. I loaded up 25 rounds with the opened up flash holes to try against 25 rounds of previously loaded ammo that does not have the uniformed holes. This load will be 24.4 grains of 3031 since that is what I had already loaded. My hole will be the .086" hole against what ever is in the previously loaded ammo. I will be shooting it out of my 18" Ruger American in .223. The gun is already pretty accurate but I'm always looking for just a little more. I was pretty impressed where the spent brass was landing when shooting the Mini 14 and the AR today so I know something changed.

I am not brave enough to go to a 3 mm hole so I will be watching.

kwg


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Re: flash holes in brass [Re: kwg020] #16438190 Yesterday at 06:36 PM
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28%! I'm surprised. Following this thread with interest.


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