Primer "hole" size?
- Thread starter Prof Young
- Start date
I was reading about that last night. Large/Small primer hole. Was a good write up on it. Originally thought that the smaller hole would give a laser (tighter diameter) type fire thru the powder for a more fast consistent velocities. Some still think it doesn't, while others say yes. Even had pics of the fire coming out of the (primer only) casing, measuring the length of the fire.
Yosemite Steve
New member
That's a pretty huge difference.
If it were me I would load up some rounds with each type of brass and record differences. I am interested to know more about this.
If it were me I would load up some rounds with each type of brass and record differences. I am interested to know more about this.
I have seen some of that in pistol before but no idea why. Will a normal .080 depriming pin fit through the small one?
If that were a rifle case I would say it is a Palma size flash hole or .059 size hole. Longer primer pocket life and better ignition in the longer rifle case in theory.
Being that it is pistol I would have to think it was for ignition purposes being that pistol cases tend to have a lot of space inside the filled case. Larger hole would make a wider flame maybe and give a more uniform powder burn. Just guessing here
If that were a rifle case I would say it is a Palma size flash hole or .059 size hole. Longer primer pocket life and better ignition in the longer rifle case in theory.
Being that it is pistol I would have to think it was for ignition purposes being that pistol cases tend to have a lot of space inside the filled case. Larger hole would make a wider flame maybe and give a more uniform powder burn. Just guessing here
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Prof Young,
This is the site I was reading about this. But it is "flash-hole" as Mike38 stated, but I found it when googling large vs small pocket size.
http://bulletin.accurateshooter.com/2013/05/large-vs-small-flash-holes-in-308-win-brass/
Hope this helps.
This is the site I was reading about this. But it is "flash-hole" as Mike38 stated, but I found it when googling large vs small pocket size.
http://bulletin.accurateshooter.com/2013/05/large-vs-small-flash-holes-in-308-win-brass/
Hope this helps.
Large flash may increase velocity?
See primer size vs velocity, large vs small primers in 45 acp.
https://www.starlinebrass.com/articles/Small-Primer-vs-Large-Primer/
See primer size vs velocity, large vs small primers in 45 acp.
https://www.starlinebrass.com/articles/Small-Primer-vs-Large-Primer/
Larger flash holes are used for NT primers (non toxic) which require a larger flash hole to insure good ignition. Too large a flash hole can increase pressure on the primer and fore it out of the pocket. I've found some 45 ACP brass marked "NT" on the headstamp to have larger flash holes and some used small pistol primers...
Thanks to the OP for opening an interesting discussion. I think I have learned more about primers and primer cups in the last few hours than I could imagine. There is a 3 part article by Laurie Holland editor of in Target Shooter Magazine where she does a indepth primer review including small primer and small flash hole vs large rifle primer tests. I found it earlier and plan on doing a reread or two later on.
It's one of those articles I read then reread a couple of times and discover something new each reread. It seems obvious that the choice of primer make and size can make a major difference in velocity standard deviation and group sizes even at close range
SMALL RIFLE PRIMER PERFORMANCE IN THE 308 PALMA CASE BY LAURIE HOLLAND
Part1- http://www.targetshooter.co.uk/?p=2613
Part 2- http://www.targetshooter.co.uk/?p=2621
Part 3- http://www.targetshooter.co.uk/?p=2613
I am doing a load workup on my .260 this week with some Peterson brass with the Palma style small primer and small flash hole early next week. Looks like I will be playing with the make and model of the primers also
It's one of those articles I read then reread a couple of times and discover something new each reread. It seems obvious that the choice of primer make and size can make a major difference in velocity standard deviation and group sizes even at close range
SMALL RIFLE PRIMER PERFORMANCE IN THE 308 PALMA CASE BY LAURIE HOLLAND
Part1- http://www.targetshooter.co.uk/?p=2613
Part 2- http://www.targetshooter.co.uk/?p=2621
Part 3- http://www.targetshooter.co.uk/?p=2613
I am doing a load workup on my .260 this week with some Peterson brass with the Palma style small primer and small flash hole early next week. Looks like I will be playing with the make and model of the primers also
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Prof Young
New member
Thank you Zeroed and Houndawg . . .
Thanks for the good links to informative articles. So much to learn! It's called a flash hole. Right. I knew it had a name but didn't bother to figure that out.
Life is good.
Prof Young
Thanks for the good links to informative articles. So much to learn! It's called a flash hole. Right. I knew it had a name but didn't bother to figure that out.
Life is good.
Prof Young
Emerson Biggies
New member
I was researching a similar thing at the SAAMI site last week. Their mechanical drawings of the 223 Remington case does not have a specification on the flash hole. Further checking of other brass in my possession was also without data. You'd think the flash hole would be part of the data package for any caliber. Go figure.
It depends on the type of pin you're using. A flat-tipped depriming pin will usually jam in the flash hole. I've had that happen while depriming once-used Guat 5.56 surplus. A rounded-tip depriming pin will usually knock out the spent primer without jamming in the flash hole but will jam about 25% of the time.
This is just my wandering mind.
In the old days it was a flash hold because that's where the trail of powder went in a gun.
The terminology never changed but in reality it is a Primer hole.
Technically if the powder cover the hole, grains are small enough (ball) then you have a short trail of powder.
I managed to get a case into a group with no primer a while back, nothing came out the primer hole.
So, If a man says something in the forest and there is not a woman to correct him, is he still wrong?
In the old days it was a flash hold because that's where the trail of powder went in a gun.
The terminology never changed but in reality it is a Primer hole.
Technically if the powder cover the hole, grains are small enough (ball) then you have a short trail of powder.
I managed to get a case into a group with no primer a while back, nothing came out the primer hole.
So, If a man says something in the forest and there is not a woman to correct him, is he still wrong?
While each brass manufacturer determines the size of the flash hole, there are three sizes that predominate among boxer primed brass. Most boxer primed brass encountered in the United States uses the largest of the three. Decapping pins designed for that larger flash hole may bind in a smaller flash hole.
As far as the effect of the flash hole size on ignition, it may be enough to be a concern to the shooters looking to shoot five-shots and end up with one-hole, but I have never noticed any difference in ignition reliability, velocity or variability of velocity on any of my ammunition (as determined by a 1992 vintage Shooting Chrony). In my experience there has been more difference between primer brands than there is in using the same primer brand with differing flash hole sizes.
Of course, if having smaller than normal flash holes causes a problem, you could always get an appropriate sized drill bit and drill the flash holes out.
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I suppose it doesn't if your idea of a good group is 1 inch at 25 yards then it does not matter. But for precision shooting it certainly seems to
I would not recommend drilling them out either. If you are buying Palma style cases then it should be expected they will have .060 flash holes
http://www.targetshooter.co.uk/?p=2613
I suppose it doesn't if your idea of a good group is 1 inch at 25 yards then it does not matter. But for precision shooting it certainly seems to
I would not recommend drilling them out either. If you are buying Palma style cases then it should be expected they will have .060 flash holes
http://www.targetshooter.co.uk/?p=2613
Now that is a snoot full. Be interesting when Unclenick weighs in.
I struggle with veracity when you see things like moisture will do in a primer though and we know they are pretty impervious.
Is there such a thing as a cool dry place in Mississippi short of a fridge?
I wish the write would say, keep as reasonably dry and out of the direct sunlight as possible.
Is exploding plastic cases more desirable than metal?
It would be good to be clear Primers are an explosive and smokeless powder is not.
I would not want to pack any case full of an explosive metal or not.
And Aside:
We were home remote taught correspondence course on a State program where we lived for a few years (no school)
They had us write 3 times a week a two page report.
To this day I can write a two pages report on a nail (not that it would be interesting!)
Rebellion ensued one lesson when they forgot to include a male related subject and the directive for that report was My Favorite Doll.
My mother was a very capable and smart woman, came up with a replacement subject and included a note to the administrators that they needed to pay attention, facing a rebellion of 4 hard headed boys was not in a parents best interests.
I struggle with veracity when you see things like moisture will do in a primer though and we know they are pretty impervious.
Is there such a thing as a cool dry place in Mississippi short of a fridge?
I wish the write would say, keep as reasonably dry and out of the direct sunlight as possible.
Is exploding plastic cases more desirable than metal?
It would be good to be clear Primers are an explosive and smokeless powder is not.
I would not want to pack any case full of an explosive metal or not.
And Aside:
We were home remote taught correspondence course on a State program where we lived for a few years (no school)
They had us write 3 times a week a two page report.
To this day I can write a two pages report on a nail (not that it would be interesting!)
Rebellion ensued one lesson when they forgot to include a male related subject and the directive for that report was My Favorite Doll.
My mother was a very capable and smart woman, came up with a replacement subject and included a note to the administrators that they needed to pay attention, facing a rebellion of 4 hard headed boys was not in a parents best interests.