Home Forums Reloading Varmint Rifles flash holes in brass

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

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 used to use a #45 bit but just use my Lyman flash hole tool these days.

Me too…

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..

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.

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

The more expensive brass they drill the hole. It’s more consistent than that which is punched. Hasbeen

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

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.

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.

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

And folks have been uniforming their brass for how long?

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!

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








]

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

28%! I'm surprised. Following this thread with interest.

Hello all
I made it to the range again today with the brass I drilled to .086. (2.2 mm) I shot 20 rounds with the primer holes drilled and I shot 20 rounds with brass I reloaded in 2019. All of it was 24.4 grains of 3031 and Hornady 55 grain soft points. The newly drilled brass had Winchester WSR primers and the 2019 loads were primed with CCI 400 primers. They were all shot out of a Ruger American compact .223 rifle topped with a Nikon 3-9 Buckmaster scope.

Not to send up any excuses but I had a 15 to 20 mph cross wind across the range and my groups were horrible. They all strung to the left as the wind was coming from my right to the left. I had a flag at the far end of the range but it was hard to eyeball it and send one down range during a lull in the wind. The wind was also shoving the light weight Ruger around at my end as well. I shot off of sand bags from a bench. The rifle stock is a Ruger tupperware that has not been bedded.

Major observations were the group with the drilled holes was slightly better than the group without the drilled holes. The other surprising observation was the group with the drilled holes had a center that was approximately 1 inch higher at 100 yards than the group without the drilled holes. (because of the drilled holes or because of the different primers ??) The group with the Winchester primers was just over 2 1/2 inches verses 3" with the 2019 loads. In both groups I eliminated the worst flyer. I shot 12 rounds at each target at 100 yards and 8 at each 50 yard target. The 50 yard target was to make sure I was dialed in. I shot all targets using 4 round groups and a couple of minutes between groups to let the barrel cool a bit.

I also had 3 pieces of brass that got the primers punctured on the group with the CCI 400 primers. The brass was all LC brass. 2 were produced in 2017 and one is a 2012. ONE had a .073 hole and 2 had a .078 hole. The .073 hole was one of the 2017 pieces of LC brass. (go figure ?)

I'm pretty sure I have 100 of the CCI 400 primers hidden in one of my reloading boxes. I'll see if I can dig them out and try this all again sometime next week. Hopefully the wind will not be so vicious. The Winchester primers looked very much like the primers from yesterday. Somewhat flat but the rounded edges of the primers were visible. None were pierced. The CCI 400's were flat with the brass and 3 were pierced.

So far the only thing I can say for certain was how the brass landed yesterday, especially out of my Mini 14. They were a lot easier to find than in previous days since they tended to land in one spot with the brass that was drilled out to .086 verses the undrilled brass that had various sizes of holes in the brass. I know it's not very scientific but I found it interesting.

kwg

Just a thought:

1. One batch of all the same brass, 50 pieces. 25 with factory flash hole, 25 with enlarged flash holes.

2. Same powder charge, same bullet, same primer in both sets of 25 pieces.

3. Do random rows of five rounds in your ammo box - one row of five rounds is factory flash hole, another row is enlarged flash hole, and so on. BUT, have a third party load the box and not tell you the pattern.

4. Go shoot ten groups with the loaded ammo box, see if you can tell a noticable difference in group size then.

I loaded up 25 more rounds with 24.4 grains of 3031 and I found my CCI 400 primers. I had one more sleeve left. Now I have the ammo I loaded in 2019 with the undrilled primer holes and the ammo I loaded today with the drilled primer holes. Although the brass will be mixed but it is mostly 5.56 Lake City and 5.56 Winchester. I won't have the third party. It will just be me. It will be next week before I get to shoot them. Our local range is muy busy on the weekends.

kwg

Working over some 22 Hornet brass today and had a few that were hard to de-prime because the hole was smaller.

Used my flash hole tool from the inside to open them up.

My Lyman primer hole tool is .076" at it's widest point.

kwg

"uniforming" to what extent? I've never drilled out each individual flash hole. It is unnecessary. A lot of guys are searching for some magic cure to their inaccuracy problems. A little hint here, make sure there is no burr and that they are centered and fairly uniform in size. They don't have to be 3mm in size. There's a reason SAMMI spec is there. If they say a .076-.082" flash hole is acceptable (and it is), then go with it. If there was some magic in a huge flash hole, I guarantee people like Lapua would be on top of it, yet they abide by SAMMI specifications. If you guys are not producing sub moa ammo, something is wrong with your loading process, load work up process, skill or shooting technique/marksmanship (or lack thereof) or your rifle. Not because the flash hole is the wrong size. If you are unhappy with your LC brass, buy Lapua. OP, are you loading for benchrest competitions? What kind of rifle are you shooting this 223 ammo in? What kind of accuracy are you getting right now with your handloads? I'm talking consistent accuracy. 5 shot groups are almost a joke for any 223 rem. 10 shots is a better indication of what a rifle and shooter can do. I'd also take heed in what swifty52 said about drilling the flash hole too big. You could actually do some damage to your rifle, by doing this.

BSA,
You are right. I have tweaked brass many times primer pockets, deburred flash holes etc. but never enlarged the flash hole as it seems to be a complete waste of time. Where I think the OP is headed is down a rabbit hole that doesn’t lead to wonderland. Not once has he given a baseline in velocity.
Velocity = pressure just because all of a sudden a Mini14 and AR which are known to have generous chamber dimensions start chucking brass different doesn’t tell me a damn thing. I can say the same about my AR’s as I use a brass catcher. All go into a neat little pile in the bag. 😀 Did pressure go up or down? Sounds like down as it degassed his semi autos.
Whether it’s 5 shot or 10 shot groups the goal is the same shoot into one small hole. I usually run two 5 shot groups and chronograph with a 35P. I very rarely shoot the bullseye since I was taught to never shoot out your aiming point. When that’s gone you have to guess where in that hole to hold.
Also using wind as a reason for sh*t groups is no excuse. The OP sounds like he doesn’t know how to use wind flags, you shoot the conditions, waiting for a lull in winds to shoot a calm condition can be another exercise in futility.
Pick a single flag position that puts your sighters where you want them 10 ring for score or wherever on the scoring target for group and then shoot the same exact condition. A lot of times shooting full value is easier.

I applaud the OP’s efforts, but my opinion is he’s pissing in the wind.

Amen buddy. Great post.

There are a few making custom brass that use smaller than normal flash hole diameters, RMC for example. They are sufficiently small that a standard decapping pin will not fit.

Certain Lapua offerings have small flash holes too.

Lapua and others make small rifle primer brass with smaller diameter flash holes. They require a .059 pin if I remember correctly.

This looks like another test invalidating variable.

Agree .059 pin, 1.6mm = .063 so 4 thou smaller sounds about right.

Exactly

You guys are right, too many variables. I have to come up with a better plan. I don't have a chrono so there is no checking speed. As for the wind and the flag, I did the best I could with what I had. I was using a club range so there was no setting it up to my liking. Since I was by myself I didn't have someone to check the wind for me. This is a low budget project with limited resources. I'm doing the best I can with what I have. The results may be inconclusive .

kwg

I can’t cure your lack of chronograph but with the wind flags there are alternatives.
1. Get or make a 24-36” garden stake. Around here the plastic ones go for about 2 bucks.
2. Surveyors tape any color. Price on that has jumped quite a bit since I bought. About 7 bucks for 100 ft.
3. Tie a 1.5 - 2ft. Piece of tape to the stake or whatever length you want. Place the stake in a position and height where you can see it through the scope but doesn’t obscure your target. You now have a crude but visible wind flag. Make up different heights or as many as you want and place them at different yardages. Crude but effective.

I can’t help with the stakes but if needed send me your address by PM and I will send you a roll of surveyors tape at no cost to you.
Again I applaud your efforts but you gotta understand that we can be a very critical audience.

Hello Swifty
I can come up with something to hang next to my target when I go out the next time to check the wind. Our range faces due east and the last time I shot we had a strong wind out of the south. We also have a burm on the south edge of the range and the wind does all kinds of weird things once it clears the burm. It is what it is. I didn't expect MOA accuracy with the way the wind was blowing and I sure as heck didn't get it. A chrono would be nice but I have other needs for the cash. It's just a little further down the list of "must haves". The new radar chrono's have really gotten my attention but the money is not there.

When I started this my primary learning concern was; is pressure coming back through the primer hole ?. I have noticed that the CCI 400's seem to have either a softer or thinner cup than the CCI 450's and the Federal Match primers I have been shooting. I punctured 3 primers the last time I was out with the CCI 400's. I have punctured some on other rifles in the past. That is why I don't have but just a few left. I don't trust them especially with fast burning powder. When I get done with this batch I will go to the Winchester small rifle primers and pretty much start over. I should have some of the bugs (variables) worked out of the process by then.

Accuracy was and is my secondary concern but I am interested in seeing if there is an improvement. If I start puncturing primers with the .086 holed brass I'll stop post haste before I break something. If I don't break anything I'll try a slightly larger hole. I don't know if I will reach a 3mm hole. That's a pretty big hole. The study as presented by NVhnter claims up to a 28% improvement in accuracy. That's a huge claim but he had several learned fellows guiding him through the project so I am not going to doubt his word. I would settle for just a fraction of that percent.

I'm scrounging through my brass now to find something that is all matching so I can eliminate the brass variable. As for primers, during times like this CCI 400's may be the only thing on the shelf. I want to know what their limitations are and what I can do to mitigate the limitations. The other learning objective is, am I wasting my time making the holes in brass uniform in size?? Based on what I read above some folks apparently think it's worth the time and others are not doing it. We shall see.

kwg

The Speer loading manuals used to address how to use their plastic bullets in normal brass cases vs. their special plastic cases you would normally use. If I remember correctly it said you could drill out the flash holes of brass cases and using primers only, fire the plastic bullets for practice.
There was also a warning about NOT using those cases with drilled out flash holes for normal loads because the larger the flash hole, the more pressure permitted into the primer. This may be what you’re running into with the blown primers.

Here you go:
Speer maanual #13, pg 596…
“The Target-45 system is slightly different from the 38 and 44 versions. T-45 bullets are used in standard brass 45 Auto cases. Bullets are pressed into a primed, resized case with finger pressure until they stop. If primer setback occurs, open the flash hole with a 7/64” drill. Do not use these modified cases for conventional loading. Mark them with a bright, permanent color or notch the rims with a file to clearly identify them as practice cases.”

kwg,
To be clear, I had no personal involvement in the masters thesis on primer holes that I provided the link to. Just something I came across online that I found interesting and pertinent to your original post.

I would also suggest that unless your Mini-14 has been upgraded to improve it's accuracy you are wasting your time looking for improvement there. Unless yours is one of the newer target models, Minis are just not accuracy rifles. Stick to testing with your AR.

Hello NVhntr

I understand. It is a great article. Duplicating the results may be difficult. As for the Mini 14 I wanted to see if I was going to get any pierced primers. I have had them using the CCI #400's and firing them through the Mini. Like I said before, I was surprised by how the brass piled in one spot . I don't know if it was a fluke or drilling the primer hole to .086 had anything to do with it. I'm currently setting up to use my Ruger American .223 compact. It's easier to keep track of the brass than with an AR. Rain tonight, windy tomorrow with a cold front moving in and hopefully by Wednesday I can have better conditions to go try these loads.

kwg

I made it back to the range today. The wind was out of the northwest at about 8 to 10 mph and 70 degrees. It was Great shooting weather. I couldn't get on to the 100 yard range today so I had to settle for the 50. That's OK because I was working on shooting technique and getting the torque on the stock bolts adjusted to where the rifle liked it.

I pulled the barreled receiver from the stock after my last range session because one side of the stock was touching the barrel. I sanded down the offending side and put it all back together. I finally adjusted the rear Allen screw to 10-12 foot lbs of torque and the front to 6 to 8 lbs of torque while I was at the rage today. This is a SWAG based on my years in the National Guard torquing nuts on a Huey. What ever the number, I finally got it to what seems to be the sweet spot.

It turns out the brass I had drilled out to .086 shot the best 2 groups at .650". I drilled out the flash hole on 10 pieces of brass to .093. (2.36 mm) I did not see an improvement in accuracy but I only found a slight visible splash at the primer hole. So, at that flash hole dimension there does not seem to be a pressure issue. The best group for the brass drilled to .093 brass was .730. The same number as the factory hole.

It was mentioned to eliminate variables.
So, yesterday I started digging through about 3000 twice fired pieces of brass looking for nothing but Lake City brass. I think I have found enough LC17 to put together about 100 rounds of ammo with various hole dimensions. The smallest being the factory hole. I have not yet decided what the largest hole will be . Like I said, I did drill out 10 pieces of brass to .093 today and shot it at the 50 yard range. I did not get an accuracy increase. I just know there didn't seem to be any excessive pressure issues that I could find looking at the brass and the primer.

After doing a little math based on IMR's numbers 24.4 grains of 3031 delivers 52,073 lbs of pressure at the chamber.

kwg

Yesterday, while randomly picking up and inspecting once fired WW brass, I found part of the breakout from the flashhole being punched out folded back over the flashhole and obscuring part of it. Doesn't happen often but I have seen that in the past. And that's the biggest reason I uniform flashholes, especially for brass that has the hole punched.

My Lapua brass on the other hand, I don't think a guy can improve on the flashholes......

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.

kwg

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

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.



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.



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.



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.



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.



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.

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... 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

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

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

kwg

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.
kwg

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

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

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.

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

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.
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:


Been using them ever since for plinking ammo in my AR's:


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

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

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)


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.



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

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:



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

KWG,
In one of my first posts I alluded to a chronograph even a cheap pro chrono or chrony would suffice. The reason for this is that I go by the old rule velocity = pressure. You can try looking at primers or brass all you want, but it is still one of the most inaccurate ways to judge pressure, which has been proven many times over the years.

Next you don’t have to use new brass, range brass will work just fine as long as you take the time to make them as even and uniform as possible. Weigh, deburr, uniform the pockets or whatever you desire. Uniformity is the key. For your test 10 cases should be sufficient.

Take the uniform cases without flash holes modified to the range and document the velocities and any other pertinent data that load gives. This is your control group or baseline. If you want organize each case to corresponding chrono order so you know which case did what.
Now go back home take these exact same cases, one at a time to maintain proper order, drill the flasholes to your first step. Repeat range day.

Now repeat this for all steps of drilling, when all is said and done you will have data that corresponds to each change in each case. Then you can compare it.

I will not argue that deburring and uniformity of flash holes is a wasted effort because it isn’t. I will say that there comes a point in time to decide if all that work is justified by the results. For general purposes you will find that your rifle can’t really take advantage of it. I.E. accuracy increase smaller than the amount of work. I did an awful lot of thing when shooting BR whether it actually helped is debatable, but it made me feel better. For the typical varmint gun or hunting rifle it just isn’t necessary.
Conclusion is that you might be better off changing primer brand than flash hole size as I have seen large changes in velocity/accuracy by doing this. Also save your components until you can afford a chronograph. Doesn’t have to be a magneto speed, labradar or an Oehler.

Good post Swifty..

Thanks for the pictures MD. That explains a lot.

kwg

I agree Swifty. You provided good information. I'm starting to get that pressure = velocity thing. Yes, I want a chrono but it seems like something else always comes up that takes priority. I see the traditional style chrono's are getting fairly cheap. But, that Labradar looks handy and easy to use with a short set up time.

You are right about "the work justifying the results". When I was playing around with the various size of primer holes I wasn't getting the results I was hoping for after sorting brass, drilling the holes, keeping them together and getting back to the range. But, that masters Thesis as submitted by NVhunter and written by Nicolaas Martin Schrier; well, it had my curiosity up. It might of paid off for Mr. Schrier but I wasn't seeing it.

I have used several different primers. Just like everyone else when the time is right I pick up a brick or 2. I was getting Federal match primers after I wasn't getting the results I wanted with CCI 400's or 450's (for .223) but the Federal Match primers have been pretty non existent the last 11 months. This guy on YouTube got me looking at the Federal match primers. Bob's reloading: https://youtu.be/N7KVBWChnyY https://youtu.be/GaYKzLHWYvU

Has anyone had any contact or use with this brand of primer hole uniforming device? Has anyone found any improvement in accuracy ??
https://kmshooting.com/product/premium-carbide-flash-hole-uniformer-builder/

Anyway, it was interesting trying out the various primer hole dimensions but the lessons seems to be that it doesn't always matter what size the primer holes are as long as they are the same size. Just go back to the last page and see the picture that Mule Deer posted of the primer holes in the Grendel brass. Two different primer holes sizes but whey they were shot with their companion brass the accuracy was practically identical.

Enough is enough. Lessons learned.

kwg

Excellent post. In my response I purposely stated that each step is incremental in how your results will end up. Sometimes these incremental steps won't make enough difference to be detectable and other times they might, but only the person doing the reloading can determine if it is worthwhile for their purposes to pursue all the little processes that can be found in reloading research materials. I tend to do it more as experimental and as a way to relax and wind down while I am concentrating on something besides every day problems. I don't compete and I don't often share my results with others because I do these little things for myself only as a learning experience. I can't say if anyone else will find it helpful to their reloading but I find it enlightening at the least even when the results aren't earth shattering....

Bob

I know exactly what you mean when you say it's a way to relax and focus on something other than every day issues that need immediate attention. It was a learning experience for me, that's for sure. I only compete with myself. Many years ago I was an IPSC shooter and I was getting good at it. But, I got married and then kids came and that was the end of the shooting. I put all of my reloading gear up in the attic for 20 years. Most of those years I didn't have one spare nickel and I was working 3 jobs to pay the bills and pay the taxes. Now, I get to play around and make up for those 20 years.

Now that I can spend some time at the range, there are very few components. Luckily I did stock up some. Not enough, but some. Hopefully by the end of winter I can pick this back up again and play with it a bit more. I have been looking at chronographs but I really want a Labradar. But, I just hired a guy to rehabilitate a pond on the farm property. I have been talking to this guy for the last 3 years trying to set a date and a price; so, now I have to ask myself which do I want the most, the Labradar or the rebuilt pond ? The pond won.

Take care.

kwg