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I started noting the difference between primer holes on various brass and that is what brought me to this thread. The hole dimensions were all over the map with ugly rough edges on the primer holes as well. . I guess I just wanted to see if I could improve my accuracy just by taking the rough edges out and making the primer holes all the same size. I guess I opened up a can of worms.

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Last edited by kwg020; 09/23/21.

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For those people who were following this thread I have not forgotten it. It's been a busy last 2 weeks. On Friday the 24th the wife and I made a quick 5 day trip to visit a cousin who has (had) terminal cancer in Grand Junction Colorado. (923 miles one way) She passed on October 4th. 6 days short of her 74th birthday.

I did get to the range on September 29th. I had 5 bright orange 1/1/2" Birchwood Casey targets set up on a sheet of cardboard on the 100 yard range. I would like to say I saw improving accuracy as the flash holes got bigger. I didn't get that. I got flyers on targets #1, #3, #4, #5. I got a group of .880 on target #2. All of the brass was LC 17 and all cases were loaded with 24.4 grains of IMR3031. The barrel was freshly cleaned and fowled before shooting for results. The trigger pull is the factory Ruger trigger. I understand the factory sets the pull at 4.5 lbs.

The flash hole size was:
factory:#1.076 to .080
#2. 086
#3 .091
#4 .096
#5 .101

My results were inconclusive. The primary issue was flyers. All targets were shot with 4 shot groups except for #1 to sight in the scope and fowl the freshly cleaned barrel and #5 to look for pressure issues.

The last group was #5 and I fired 10 shots. Since that was the largest flash hole I wanted to see if there were any pressure issues. 3 out of the 10 pieces of brass had very flat primers with a bit of splash and the other 7 had flat primers. No primers were pierced and I had no issues with a hard to lift bolt on #5. I won't be shooting #5 with primer holes at .101 again. I don't see any value in repeating that test. I gained no accuracy and I was at the edge of pressure at the primers. The primers on target #4 had one flat primer out of 4. The other 3 pieces of brass showed no pressure signs.

As for the flyers I have no conclusions. The 4 shot groups without the flyers was 1.5". With the flyers making the groups right at 2.5" It could of been me or it could of been the flash holes, I don't know. I still have 64 rounds of ammo left. I have every intention of doing this again as soon as I can find a day with no distractions and get back out to the range.

kwg

Last edited by kwg020; 10/05/21.

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Primer hole size comparison
The final chapter


ON Monday October 25th I got the chance to finish this primer hole size comparison. The day was sunny and cool with light and variable winds. I was still using my Ruger American in .223 for the testing. My primers were Winchester small rifle and the powder was 24.4 grains of IMR 3031 and a 55 grain Hornady soft point as the bullet. All shots were made at 100 yards.

I have always thought of IMR 3031 as a great powder and can make almost any rifle accurate. I know it is stick powder and with that in mind it is not the perfect powder for use in most powder measures. With that in mind after I dropped the powder into the LC17 cases, any case that appeared to have more or less than the “average” amount of powder in it, I dumped it out and re poured it. Using just a visual check I was pretty happy that I got very close to 24.4 grains of 3031 in each case.

I did run out of LC 17 cases. With that in mind in the cases where there was NO modification of the primer hole I used LC 16 cases. To re-cover some already plowed ground, the LC 16 and the LC 17 had a primer hole between .076 and .080” in diameter. The LC 17 cases I drilled out to .086”, .091” and .096”. In just a minute I will talk about stock screw torque.

Flyers


I shot 8 additional rounds at every 1” target that I started on Tuesday October 5th for a total of 12 rounds on each target. With the factory drilled (punched) holes I got a 2” group and 3 flyers that took the group to just over the 3”.
The 12 shots made at the #2 target were with LC 17 brass and the primer hole was drilled to .086”. This was my best group. Just like on Tuesday the 5th. 11 shots fell into a 1.725” group. I had one called flyer that took the group to right at 2”.

Group #3. This brass had the primer holes drilled to .091”. 7 shots were into a group at 1.52”. The other 5 shots were flyers with the furthest shot being 2.60” from the point of aim. Similar to what I experienced on Tuesday the 5th.

Group#4. This brass had the primer hole drilled to .096”. 8 shots were into a group at 1.58”. The other 4 shots were flyers with the furthest out at 2.75” from the point of aim.

Stock screw torque


I mentioned stock screw torque. I pulled the stock and the action apart after shooting on Tuesday the 5th to see if I could get the trigger pull reduced. With the turn of an Allen screw I did get the trigger pull reduced on the Ruger American factory trigger. It appears the lowest trigger pull weight a person can get with a factory trigger spring setup is 3.5 lbs. That seemed to be the results I got. Although, I did get just a bit of trigger creep after turning the weight down.

An even more frustrating problem is getting the screw torque back to where it was before taking the gun apart. Before shooting for groups I had to play with the stock screws in order to find that torque “sweet spot” I had before. This required firing a group and then checking the size. I never got back to where I was before taking the two halves apart. I don’t own a torque wrench, at least I didn’t then, but I do now. I bought one from Midway and I’m waiting for it to arrive. I’m sure this added to the dismal group size I eventually got. Yes, I did create a variable. A big ugly variable. In retrospect I wish now I’d of left the trigger alone.

The perfect load and bullet combination


I have always had good luck with 3031 and getting good groups. I’m not sure the combination of the 55 grain Hornady soft point and 3031 was the right bullet, primer and load for this rifle. If I continue to play with primer hole size I need to change up the powder/primer/bullet combination.

Unexpected issues


After firing each 4 shot string I checked the primers for flatness. I had no primers punctured. Even with the .096” primer holes. The primers were flat with the base of the brass, but no punctures. I did notice some horizontal lines on the brass that had the primers drilled out to .096”. When I got home I checked the insides of the brass with my bore scope. I found 5 of the 3 times fired brass with the beginnings of a case separation out of 20 pieces of brass (25%) The brass that was drilled to .091 had 4 pieces that were beginning to separate and the brass that was drilled to .086 had one piece that had the beginnings of a case separation. There were none in the brass that had the factory punched holes. Again, this was brass that had been loaded twice before and this was the third fired load.

IN retrospect


I should of never pulled the stock from the receiver to adjust the trigger. This changed everything as far as accuracy goes. Hopefully, finding that sweet spot again comes quickly after getting the torque wrench.

Making the primer holes uniform in size did seem to pay off, as long as you don’t go too far. The .086” holes performed the best. This is between .006 and .010” larger than the factory punched holes. The primers were not flat or punctured but apparently it did change the dynamics of the powder ignition and caused a near separation in one piece of brass. The larger the primer holes the more brass that was very close to separating.


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I've always seen brass uniforming as an incremental process. Each step of the process gets a small amount of improvement in consistent ignition which may or may not be noticeable by itself, but if you take each step and add them together once you get to your desired goal, you can notice the difference if you are paying attention and keep a few loads available without the improvements as a 'control" group...

Quite a few years ago I bought a flash hole deburring tool and started using it on any new brass or once fired brass I was reloading for the first time. The one I got has an adjustable tapered head to keep it centered in the case mouth and a tapered cutter for the internal flash hole with a tube around the exterior that acts as a stop when it hits the bottom of the case. Memory is the second thing to go, so I can't remember where I bought it... In any case, I found some brass would take a quick twist of the wrist to clean and deburr the flash holes and would remove very little brass. Others would take a couple turns and I would dump out several pieces of brass burrs that were removed. It was a pain doing 300-400 pcs of brass in a go, but you only have to do it once for each piece of brass so I keep it as one of my reloading rituals... wink I did notice once done the flash holes seemed more round and concentric once deburred...

What I found was that many of my more fussy cartridges became a lot more consistent with their groups and for the most part a bit more accurate. It wasn't a lot of difference, but enough to notice. Once I started getting a little more anal about measuring my loads, brass prep, seating bullets as straight as possible, and other things I'm sure most of us do, I did notice a real difference in how several of my rifles would group. But I believe that deburring the flash holes was a big impact on how my reloading improved my groups. Even if I did drill my flash hole, I would still deburr the interior as even the best drill bit will probably leave a bit of burr and i always thought that was the most inconsistent step in the whole ignition process... interrupting the primer flame shape with a burr IMO can cause inconsistent powder burn... I'm pretty sure I read that somewhere from somebody a lot smarter than me, but it makes sense IMO...

Bob


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Originally Posted by Sheister
I've always seen brass uniforming as an incremental process. Each step of the process gets a small amount of improvement in consistent ignition which may or may not be noticeable by itself, but if you take each step and add them together once you get to your desired goal, you can notice the difference if you are paying attention and keep a few loads available without the improvements as a 'control" group...

Quite a few years ago I bought a flash hole deburring tool and started using it on any new brass or once fired brass I was reloading for the first time. The one I got has an adjustable tapered head to keep it centered in the case mouth and a tapered cutter for the internal flash hole with a tube around the exterior that acts as a stop when it hits the bottom of the case. Memory is the second thing to go, so I can't remember where I bought it... In any case, I found some brass would take a quick twist of the wrist to clean and deburr the flash holes and would remove very little brass. Others would take a couple turns and I would dump out several pieces of brass burrs that were removed. It was a pain doing 300-400 pcs of brass in a go, but you only have to do it once for each piece of brass so I keep it as one of my reloading rituals... wink I did notice once done the flash holes seemed more round and concentric once deburred...

What I found was that many of my more fussy cartridges became a lot more consistent with their groups and for the most part a bit more accurate. It wasn't a lot of difference, but enough to notice. Once I started getting a little more anal about measuring my loads, brass prep, seating bullets as straight as possible, and other things I'm sure most of us do, I did notice a real difference in how several of my rifles would group. But I believe that deburring the flash holes was a big impact on how my reloading improved my groups. Even if I did drill my flash hole, I would still deburr the interior as even the best drill bit will probably leave a bit of burr and i always thought that was the most inconsistent step in the whole ignition process... interrupting the primer flame shape with a burr IMO can cause inconsistent powder burn... I'm pretty sure I read that somewhere from somebody a lot smarter than me, but it makes sense IMO...

Bob

I have not gone from the case mouth side and deburred the inside of the case. It does sound logical. I'm going to rethink my load and bullet and maybe give it another go next spring. I'll have the winter to collect and sort brass then drill the primer holes. The biggest issue I did not think of was how the powder explosion affects the case itself. I was looking at primers and I probably should of been looking at the insides of the case looking for stress cracks.

kwg


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This video shows the process pretty clearly. I don't buy high end brass for my purposes since I don't compete, so at times my deburring tool can take off a lot of burr material... if you look closely, you can see the cutter gives you a nice tapered internal flash hole for an even flame path. I've always thought this was pretty important for consistent ignition, especially with fast powders or large cases with a large charge of slower burning powder...

My deburring tool is an older model of the Sinclair tool, but works the same and adjusts the same as the one shown in the video


Last edited by Sheister; 11/01/21.

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I have the Lyman version of that tool. I just haven't used it.. I should dig it out.

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Now and then I have brass on hand that has undersized flash holes. Don’t know why some jokers make such stuff but when primer punch hits a wall, out comes the drill. .080” diameter. Life is normal afterwards and my Tourette’s fades away.


I am..........disturbed.

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Originally Posted by DigitalDan
Now and then I have brass on hand that has undersized flash holes. Don’t know why some jokers make such stuff but when primer punch hits a wall, out comes the drill. .080” diameter. Life is normal afterwards and my Tourette’s fades away.


Good answer. I have settled on the #45 drill. It's a .082 size hole for .223. After getting several separated cases with larger holes and little additional accuracy I don't see the logic of going any bigger.
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If bigger flash holes were better, don't you think after all these years, ammo manufacturers would have figured that out? I've never once had to drill out a flash hole. Ran into some rough burred ones and my torch tip cleaner fixes that right up. That's what I use to poke the stuck media out with and while I'm at it, also remove burrs. 2 birds with 1 stone. Nothing too complicated there.


Originally Posted by raybass
I try to stick with the basics, they do so well. Nothing fancy mind you, just plain jane will get it done with style.
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Originally Posted by bsa1917hunter
If bigger flash holes were better, don't you think after all these years, ammo manufacturers would have figured that out? I've never once had to drill out a flash hole. Ran into some rough burred ones and my torch tip cleaner fixes that right up. That's what I use to poke the stuck media out with and while I'm at it, also remove burrs. 2 birds with 1 stone. Nothing too complicated there.


I dug my Lyman's primer hole burr tool out and went through probably 700 cases in the last 2 days. All were 5.56 brass of some kind. Mostly Lake City. I did run my #45 drill bit through the primer hole prior to using the Lyman tool and found that most of the holes were very clean with clean smooth edges after being drilled. I really didn't need to do anything additional but I had the time and wanted to see just how many cases needed to be reamed from the inside.

The few I did find that were not clean with smooth edges were mostly the dated FC (Federal Cartridge) 5.56 brass. They had the roughest internal holes. I looked at them with my bore scope and could see that they were not very smooth even after running the #45 bit through the holes. It would of taken a much larger drill bit to clean them up as nice as the other 5.56 brass I cleaned up with the Lyman tool or by drilling them out.

It appears the options are:
I can make the primer holes uniform and get rid of the rough edges on the drill press or spend the time to clean them up with the Lyman tool by hand. All except for the FC 5.56 brass which seems to be an animal of it's own. The fastest way was to simply lift the primer hole up to the spinning drill bit on the press and run it through. Just that quick and it was done.

kwg


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Originally Posted by bsa1917hunter
If bigger flash holes were better, don't you think after all these years, ammo manufacturers would have figured that out? I've never once had to drill out a flash hole. Ran into some rough burred ones and my torch tip cleaner fixes that right up. That's what I use to poke the stuck media out with and while I'm at it, also remove burrs. 2 birds with 1 stone. Nothing too complicated there.


On top of that it appears that the best made brass for cartridges used in the most precise competition disciplines often has deliberately small flash holes.

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Originally Posted by mathman
Originally Posted by bsa1917hunter
If bigger flash holes were better, don't you think after all these years, ammo manufacturers would have figured that out? I've never once had to drill out a flash hole. Ran into some rough burred ones and my torch tip cleaner fixes that right up. That's what I use to poke the stuck media out with and while I'm at it, also remove burrs. 2 birds with 1 stone. Nothing too complicated there.


On top of that it appears that the best made brass for cartridges used in the most precise competition disciplines often has deliberately small flash holes.

I'm also sure with the best brass the holes are consistently the same size. That seems to be a key to accuracy.

kwg


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kwg020,

I happened to make a somewhat inadvertent comparison of flash hole size a few month ago, when doing a lot of shooting with a CZ 527 in 6.5 Grendel, which typical of CZ rifles was quite accurate.

The first batch of brass I could find was Norma, which proved to be quite consistent in dimensions. Worked up a bunch of loads--and then came across a batch of Starline brass, so bought it too, which also proved to very consistent dimensionally, with one exception. It turned out the Norma brass had standard small primer flash holes, and the Starline had large rifle flash holes. (Both had small primer pockets.) All the flash holes were well centered.

So I retried three of the loads worked up with the Norma brass in Starline brass. There wasn't a consistent difference in accuracy--in two loads the Norma-brass loads shot more accurately, and in the other the Starline-brass load did.

The weight of both brands of brass averaged almost exactly the same. For 10 randomly selected case (all trimmed to the same length), the Norma brass averaged 111.1 grains, varying .6 grain. The Starline brass averaged 110.9 grains, varying .5 grain.

Despite the difference in flash hole size, muzzle velocity was for all practical purposes identical. Same deal as with the accuracy--in two loads the Norma brass averaged "faster," by 7 fps and 5 fps. In the third the Starline brass was 8 fps faster. This is less variation than the SAME load often chronographs in different strings during the same range session.


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Originally Posted by Mule Deer
kwg020,

I happened to make a somewhat inadvertent comparison of flash hole size a few month ago, when doing a lot of shooting with a CZ 527 in 6.5 Grendel, which typical of CZ rifles was quite accurate.

The first batch of brass I could find was Norma, which proved to be quite consistent in dimensions. Worked up a bunch of loads--and then came across a batch of Starline brass, so bought it too, which also proved to very consistent dimensionally, with one exception. It turned out the Norma brass had standard small primer flash holes, and the Starline had large rifle flash holes. (Both had small primer pockets.) All the flash holes were well centered.

So I retried three of the loads worked up with the Norma brass in Starline brass. There wasn't a consistent difference in accuracy--in two loads the Norma-brass loads shot more accurately, and in the other the Starline-brass load did.

The weight of both brands of brass averaged almost exactly the same. For 10 randomly selected case (all trimmed to the same length), the Norma brass averaged 111.1 grains, varying .6 grain. The Starline brass averaged 110.9 grains, varying .5 grain.

Despite the difference in flash hole size, muzzle velocity was for all practical purposes identical. Same deal as with the accuracy--in two loads the Norma brass averaged "faster," by 7 fps and 5 fps. In the third the Starline brass was 8 fps faster. This is less variation than the SAME load often chronographs in different strings during the same range session.


Now now MD don’t go throwing in actual velocity difference in the mix. But as usual you brought actual documentation into the mix. 😁
This takes me back to my original problem with this whole thing. He has no base line of where he was to compare against where he went.
Accuracy can be very finicky. One day you are printing tiny groups and the next not so tiny. Maybe your head isn’t in it or maybe you just aren’t reading the conditions as well as the day before. To say that I drilled out the flash hole to this size and got a micro group size doesn’t say a thing. Especially when that could have been a fluke. Did the flash ole cause the ES/SD to drop dramatically, did velocity go up or down that could have put him into a node? Did he use that exact same brass on each step? Too damn many variables are left out to draw a firm conclusion.

Either way without some control set or baseline to validate what the changes did or didn’t do, makes the whole thing as Willy nilly play time.



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Originally Posted by Mule Deer
kwg020,

I happened to make a somewhat inadvertent comparison of flash hole size a few month ago, when doing a lot of shooting with a CZ 527 in 6.5 Grendel, which typical of CZ rifles was quite accurate.

The first batch of brass I could find was Norma, which proved to be quite consistent in dimensions. Worked up a bunch of loads--and then came across a batch of Starline brass, so bought it too, which also proved to very consistent dimensionally, with one exception. It turned out the Norma brass had standard small primer flash holes, and the Starline had large rifle flash holes. (Both had small primer pockets.) All the flash holes were well centered.

So I retried three of the loads worked up with the Norma brass in Starline brass. There wasn't a consistent difference in accuracy--in two loads the Norma-brass loads shot more accurately, and in the other the Starline-brass load did.

The weight of both brands of brass averaged almost exactly the same. For 10 randomly selected case (all trimmed to the same length), the Norma brass averaged 111.1 grains, varying .6 grain. The Starline brass averaged 110.9 grains, varying .5 grain.

Despite the difference in flash hole size, muzzle velocity was for all practical purposes identical. Same deal as with the accuracy--in two loads the Norma brass averaged "faster," by 7 fps and 5 fps. In the third the Starline brass was 8 fps faster. This is less variation than the SAME load often chronographs in different strings during the same range session.


Hello Mule Deer
Thanks for weighing in. Did you attempt to measure the size of the flash holes ? I used a set of numbered drill bits to measure the holes in the brass I shot. You also said that the Starline brass had large rifle holes and the Norma had the small rifle holes. I can't say that I knew there was a designated small rifle hole and a large rifle hole. Is this a SAAMI thing ? I just assumed each brass maker punched or drilled a hole they thought would work the best for their product. The Grendel isn't a 5.56 but I can see the relevance. I am using Lake City brass for my comparisons and I'm finding some variations in the flash hole size. The real differences comes when I see different hole sizes in other brands of brass as I'm processing my brass for reloads. Here again, maybe I'm looking at the wrong thing. Maybe I should be looking at the weight of the brass verses the size of the primer hole.

I understand Norma makes some really good brass. I don't know much about the Starline brass.

kwg


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Originally Posted by kwg020
Originally Posted by mathman
Originally Posted by bsa1917hunter
If bigger flash holes were better, don't you think after all these years, ammo manufacturers would have figured that out? I've never once had to drill out a flash hole. Ran into some rough burred ones and my torch tip cleaner fixes that right up. That's what I use to poke the stuck media out with and while I'm at it, also remove burrs. 2 birds with 1 stone. Nothing too complicated there.


On top of that it appears that the best made brass for cartridges used in the most precise competition disciplines often has deliberately small flash holes.

I'm also sure with the best brass the holes are consistently the same size. That seems to be a key to accuracy.

kwg

Consistency is key. Whether small or large. Keep them all roughly the same size and clean and free from burrs and you'll be just fine. Now, I've seen flash holes off center and that may create an issue. I generally toss those in the scrap bin.
Originally Posted by kwg020
Originally Posted by bsa1917hunter
If bigger flash holes were better, don't you think after all these years, ammo manufacturers would have figured that out? I've never once had to drill out a flash hole. Ran into some rough burred ones and my torch tip cleaner fixes that right up. That's what I use to poke the stuck media out with and while I'm at it, also remove burrs. 2 birds with 1 stone. Nothing too complicated there.


I dug my Lyman's primer hole burr tool out and went through probably 700 cases in the last 2 days. All were 5.56 brass of some kind. Mostly Lake City. I did run my #45 drill bit through the primer hole prior to using the Lyman tool and found that most of the holes were very clean with clean smooth edges after being drilled. I really didn't need to do anything additional but I had the time and wanted to see just how many cases needed to be reamed from the inside.

The few I did find that were not clean with smooth edges were mostly the dated FC (Federal Cartridge) 5.56 brass. They had the roughest internal holes. I looked at them with my bore scope and could see that they were not very smooth even after running the #45 bit through the holes. It would of taken a much larger drill bit to clean them up as nice as the other 5.56 brass I cleaned up with the Lyman tool or by drilling them out.

It appears the options are:
I can make the primer holes uniform and get rid of the rough edges on the drill press or spend the time to clean them up with the Lyman tool by hand. All except for the FC 5.56 brass which seems to be an animal of it's own. The fastest way was to simply lift the primer hole up to the spinning drill bit on the press and run it through. Just that quick and it was done.

kwg

Nothing wrong with that. If it's fast and easy and it gets rid of the burr and keeps them all the same. I use a lot of FC with the scamp marks and they don't seem to be too bad. I picked up 1200 pcs one time at the local range: AKA "range pickup" brass:
[Linked Image from i.imgur.com]

Been using them ever since for plinking ammo in my AR's:
[Linked Image from i.imgur.com]

Brass prep is important. Keep everything consistent and it helps..


Originally Posted by raybass
I try to stick with the basics, they do so well. Nothing fancy mind you, just plain jane will get it done with style.
Originally Posted by Pharmseller
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You also said that the Starline brass had[b] large rifle holes and the Norma had the small rifle holes. I can't say that I knew there was a designated small rifle hole and a large rifle hole. Is this a SAAMI thing ? I just assumed each brass maker punched or drilled a hole they thought would work the best for their product. [/b]

Now how could it be a SAMMI thing?

Page 1

Originally Posted by Swifty52
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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Originally Posted by Swifty52


You also said that the Starline brass had[b] large rifle holes and the Norma had the small rifle holes. I can't say that I knew there was a designated small rifle hole and a large rifle hole. Is this a SAAMI thing ? I just assumed each brass maker punched or drilled a hole they thought would work the best for their product. [/b]

Now how could it be a SAMMI thing?

Page 1

Originally Posted by Swifty52
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.



Thanks for the update Swifty. I was unaware of the SAAMI guidelines on primer holes until you posted it. (You did post that on the first page and I plain old forgot about it until I went back and reviewed from the beginning)

To address your concerns about a baseline.

"Either way without some control set or baseline to validate what the changes did or didn’t do, makes the whole thing as Willy nilly play time"

The base line was shooting the ammo I loaded with the primer holes of LC16 and LC17 pre fired brass as drilled or punched into the brass by the manufacturer. In one of my first postings I talked about the primer holes of previously fired brass (predominately LC brass) being anywhere from .076 to .080 in diameter and did changing the diameter of the primer hole change pressure issues with the brass and secondary did it improve accuracy. Since previously fired brass (range brass) is my primary form of getting .223 ammo I thought that would be a good place to start because it was what I had the most of.

I certainly wish I could afford brand new high quality virgin brass every time I set out to load some more ammo. I just don't have the money and resources to do that. And, why would I do that when I have access to gobs and gobs of once or twice fired brass that is free to me as left behind on the range. With that in mind, I did compare unmodified factory range brass to the brass I drilled the primer holes in to different dimensions. (.086, .093, .098 and .101) I used the unmodified brass as my base line. It was the first group I shot at the top of target. Since this brass was fired twice before I was looking for pressure issues first and was it more (or less) accurate than the primer hole modified brass ?

On 09/14/21 NVhunter introduced us to a masters thesis as written by Nicolaas Martin Schrier. Nicholas wrote this thesis in 2015. (This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources) https://scholarsmine.mst.edu/cgi/viewcontent.cgi?article=8415&context=masters_theses

The question about the pressure (which was my primary question) issues was eventually solved the third time I went to the range on 10/05/21. I discovered that the larger the primer hole the more likely I was going to have case separations. (case separations indicate pressure issues to me, I assume it means pressure issues to you as well) When I had 5 cases out of 20 that had obvious separations inside of the brass that could be seen with a bore scope in the brass I drilled to .098". The brass I drilled to .101 I only fired at the second outing. (10 rounds) AS I recall the primers were very flat on that brass but the primers were not punctured. I simply tossed that brass without looking at the inside of the case. I can only imagine what it looked like internally had I looked.

If it weren't for one vertical line on one piece of brass I probably wouldn't have looked as I was only looking at the primers. Since I was shooting a bolt gun I saw no swipe marks on the base of the brass nor did I see any ejector marks on the brass. After checking all the brass I found 4 more cracked cases on the brass I drilled to .093". All of those cases were tossed into the scrap bucket.

I also mentioned that I took the rifle apart to lighten up the trigger. I did lighten the trigger but I should of left it alone. This ultimately was a huge mistake on my part as I could not get the stock screw torque to settle in and the rifle did not shoot as well on my second trip to the range with the Ruger American as my first trip to the range with the RAR. I introduced a variable that I could not correct. I did use 8 rounds per group to find this "sweet spot" again which left me 12 shots per target. (Next time I will try not to be as dumb)

So to rehash

There were no pressure signs on the brass either outside or inside that was drilled by the factory. (.076 to .080") (I shot 12 rounds per group but 20 rounds total)
There was 1 case that had started to separate that had the primer drilled to .086" out of 20 rounds shot. (12 shots per group and 20 rounds total)
There were 4 cases that started to separate out of 20 rounds shot that had been drilled to .093" (12 shots per group and 20 rounds total)
There were 5 cases that started to separate out of 20 rounds shot drilled at .098". (12 shots per group for 20 rounds total)

I got my best accuracy out of the cases that had the primer hole drilled to .086. I think mostly because every primer hole was the same and it was relatively close to the factory dimensions.
The next best accuracy was the target with the factory drilled primer holes.

The brass that had the primer holes drilled to .093 and .096 had flyers. Some worse than others. So, along with the pressure issues and the flyers, there appears to be no value in drilling a primer hole that big in .223/5.56 range brass if keeping pressure in check and if accuracy is your goal.

Lessons learned


Making the primer holes uniform in size is a good thing if you have previously fired brass that has been unmodified and has various sized primer holes.

There are probably going to be pressure issues if you go too large. I consider too large .006" over the .080 in .223/5.56 brass because there is a chance a person can start getting pressure stressed cases. Even though the primers do not look stressed. The ammo I drilled the primer holes out to .086" was my most accurate ammunition.

IN order to make all holes uniform I have been using a #45 drill bit that gives me .082" sized holes. I understand this is .002" over the SAAMI recommendations as provided by Swifty but checking with the bore scope I am finding that the .082 holes remove a vast majority of irregularities inside of the brass case and make for nicely smooth primer flash holes.

I may pick this up again next spring. But, enough for now.
kwg


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kgw20,

I measured the diameter of the flash holes by inserting a long, gently tapered steel "needle" and measuring the diameter where the needle stopped. But here's a photo of the basic difference, which appeared with the article:

[Linked Image]

To tell the truth, guys like you are one reason I don't post very often outside of the "Ask The Gunwriters" and "Free Classified" forums. You apparently have little comprehension of how to test handloads at least semi-scientifically, by focusing on certain variables during your tests, and trying to control them as much as possible. Swifty and others have tried to point this out, but you're not really getting it.

There's a lot of good information out there on all of this, but apparently (like many these days) you prefer to wing it without doing much research beforehand--and then post on the Internet asking questions (and posting "test" results) that indicate your lack of previous research and understanding.

MD


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