Flash hole deburring and primer pockets

H

hounddawg

New member
In another thread flash hole deburring was mentioned. The only test I have seen on the practice was in by Litz ( is he the only one that actually tests these theories ?) and he found that if you are using brass with punched flashholes not drilled deburring produces a significantly lower SD of velocity but any chamfering of the flasholes resulted in a increase in SD (Modern Advancements in Long Range Shooting) Tony Boyer in his book on Rifle Accuracy is skeptical on the usefulness and points out that after the initial firing any burrs are flattened anyway.

I take the safe route and never use virgin cases at a match or in testing and let the primer deburr the flash hole on the first firing. I do uniform primer pockets however. I have see variations in all brands including Lapua and want my primers seated to the same depth so I take a few minutes to do so.

Just curious as to who does what to the primers and flasholes and why? Any links to actual testing data would be wonderful
 
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I have never found a burr at the exit hole; because of the infatuation reloaders have with flash holes I purchased RCBS deburring tools with attachments. The one thing I do know about the tools is; they are sharp.

And then there are other things reloaders do not get into that I consider more important. To avoid boring other reloaders I will continue dealing with flash holes in my own way.

F. Guffey
 
I for one can attest that Tony Boyer would be 100% incorrect.
At least when dealing with RP, or Win casings in 7mm Rem Mag.
You can feel the deburr tool catching.

I would also point out that after uniforming the primer pocket, and uniforming deburring the flash hole on the primer side, and on the inside of the casing, i noticed no spreading on ES/SD. Seemed to be more a combination of primer, powder, bullet combo.
Example.
Stevens 200 chambered in 7mm-08 Improved 40 degree. (7mm SGLC).
140 gr. Berger VLD
PPU casings
Fed 210M primers
Unspecified charge of Alliant Power Pro 2000.
ES of 7 fps (20 rounds)
SD of 2 fps (20 rounds)

Same could not be said of any other powder/bullet/primer combo out of that, or any of my other rifles.

As Mr. Guffey rightly suggests, i more than likely do not do things that i could/should do.
But at the same time, i'm not heavily into match shooting, most of my rifles are for hunting. And sometimes good enough is good enough. Perfection can be a PITA.
 
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Somewhere floating around on Bullseye-L-forum & maybe 1911Forum one of the noted shooters did some testing on what was and what was not beneficial to bullseye shooting . It seems to me that squaring the primer pocket was beneficial but de-burring the flash hole on the inside was of no consequence.
 
I have found dubbers on the inside, butnot a lot. I don't shoot competition so I have no way to evaluate their impact one way or another. So like Smokey Bear used to say, Only you can prevent dubbers.
 
First, I'll confirm what Std7mag said. I've deburred lots and lots of Lake City cases that were once-fired and still had their burrs well-preserved. I can imagine how, if the case had a compressed load, that pressure building in the center might cause powder grains adjacent to the burr petals to press back against them momentarily. I just haven't noted it for myself. I'd probably have to use a bore scope to do a before and after.

In my experience, whether or not you see an effect depends greatly on what powder you are using. Using Remington cases in my M1A, I found it would shoot 168-grain SMK's into about 0.75 moa with all the stick powders I tried in it. When I tried Accurate 2520, though, a load that had the poorest loading density of those I tried, the groups opened to about 1.25 moa. When I deburred the flash holes, they went down to about .75 moa like the other powders. Back then (early 90's) I was using Federal 210M primers and was unaware of the value of CCI magnum primer reformulation with spherical powders, so I don't know if I'd have got the same result using them or not. I can say for sure, though, that it made an astonishing difference with standard primers at the rear.

When I read Litz's observation about chamfering it reminded me mine were chamfered as the nose of a center drill was used to make the tool I have. It sounds like a pilot in an end-cutting end mill would be better.

One of the problems with burrs I ran into was that my Dillon Super Swage 600's anvil would tend to flatten them down (good), but sometimes bend them over the flash hole (bad). If you use a swaging tool with an anvil to remove military crimps or to widen tight CIP spec flash holes, you want to do any flash hole reaming or drilling afterward. Makes me wonder if the best way to remove burrs might just be tapping the end of one of the Lee hand decapping rods against the bottom rather than cutting at all. Something else to try.
 
Litz is not the only one who tests theories. But theories require a lot of data to be proved conclusively true or not, and even Litz's observations are skewed. He does not typically use low quality brass or components. So, given his set of conditions, sure, he is probably right, but that does not mean Boyer's, or Unclenick's observations are incorrect.

I am close to 1M rounds loaded and I am still learning. But across all calibers, I think it is safe to say that consistency in ammo leads to accuracy. COAL and neck tension are the two areas where most reloaders can improve their accuracy, and lower their SD. As to flash holes and primer pockets...With low quality brass, it will be inconsistent in other areas so I largely think de-burring flash holes and uniforming primer pockets is not worth it there, and with quality brass I have never seen the de-burring tool do anything. Mine mostly sits in a bin on the bench and the primer pocket uniformer on the brass prep station is more to make sure all the carbon is out than to cut any brass.
 
The link gives a 404 error. Not that it matters.
Burrs on primer holes will not make a lick of difference to accuracy. Very much doubt 'uniforming the primer pocket' does anything but sell tools either. At least not for regular match ammo. It might for Bench Rest ammo, but not likely.
 
link fixed

All I use these days is Lapua, it is the best cost effective cases I can find. I experimented with others such as Peterson and Alpha but the Lapua case/primer pocket life makes it the best bang for the buck. This is just more a hypothetical than anything for me. For whatever it is worth I definitely see better consistency from once fired brass than new, even Lapua
 
Like Howndwagk, I too feel for my shooting that once fired are better than new.

I also have shot Lapua with RP in direct loads and varying loads.

Never saw any difference between them and a fondness for RP that may be misplaced but close enough.

I strongly suspect you have to shoot holes in 1 to see any difference.

If I am never going to shoot 5 x one hole (or randomly) its not worth the mussing with.
 
I live by the theory that I should be able to control all mechanical portions of my reloading process. If I do that with consistency then my ammo will shoot as consistently as possible. That said, I now only use Lapua or Norma brass and the brass only gets used in one rifle. I sort all my brass and if I come across a primer hole that has a burr it becomes suspect and goes into my plinking brass bucket.
 
I spend time preping my 308 cases , first time I'll uniform the primer pockets deburr the flash hole inside an out , use a #45 drill bit to uniform the flash holes to the same size . I want my cases to be as close to exact as possible . Size all the cases to the same measurement ( headspace ) then trim to the same length every firing . Using the RCBS Full Length Die with the Expander ball along with the Redding Competition shellholder set of 5. Works for me .
 
Many years back my folks were coming home from 220 miles South, got to about 130 South and the engine in the car started making god awful noises.

I get the call, we are stuck down here can you come down and rescue us and we don't want to leave the boat down here.

Sweet, I get to help them out after all these years of them raising me.

Get the hitch, get the wire cutters and wire nuts as my plug does not mach theirs, bean bag in the back of the 1973 Bronco (no rear seat) and off to the rescue.

My mom was delighted with the bean bag (back in the day before air bags) and we made our way home slowly (dark, pretty good load, narrow one lane road)

Ford made arrangements for the only car dealer (Chevy) in that town to tear the engine down under warranty. Nice.

A week latter we get the call, we have torn the engine down and we found absolutely nothing wrong, but it sure sounded like hell before we took it apart.

We are going to put it back together and see what happens. Yep, no noise, we simply have not idea how or what that noise was.

Its called the world of mechanical properties. Ford controlled to the best of their ability, something got out of synch tear it down and unsynched and it never made another noise again (LTD Wagon 400 cubic inch engine as I recall)

We may think we control all the variables, we really don't.

I have bought Lapua (only on sale with thoughts if I got a good load I would switch to that for shooting for affect as it were)

If its any better, its below my noise level. RP matches it head to head and may even be better.

Norma is the only one that I have read about that is truly above the good brass Norm as it were.
 
I use FC , ADI & HSM brass all are on the thick side but all three shoot the same , all cases , bullet and powder being the same . Never tried Lapua or Norma , will add them to the mix one day and see what happens .
 
Well I don't Shoot competitively but like most reloader's still seem to hold the one hole group in awe, even though I don't need it. I tried that flash hole de-burring, made my own tool to do it! Pretty simple. A drill bit epoxied into a wood handle! The only thing it's good for is de-burring a flash hole. Took the better part of four minute's to make it and I can't say it was worth the effort! My best rifle will go under 1/2" with SMK bullet's. After de-burring, that rifle still went under 1/2"! I have two 243's, a 700 Rem and a Mossberg Patriot. The case's for the 700 were de-burred and those for the Patriot weren't. both rifle's shoot into 1/2" consistently! I really don't need rifle's that accurate but I reload and it's expected! My 30-06 and 6.5x55 both go into right at 1" +/-. the 25-06 will do right at 3/4". Best group I ever shot was with the 25-06 with 100gr SMK's. Haven't shot the thing since, no way will ever match that load again! But I do have a target of the last group I shot with it! Oh yea, flash hole's were not de-burred. Something about all these little things competator's do to get and extra .005" smaller group. You can do the same thing but I doubt you can measure the group right and I sotra doubt you actually shoot well enough to make use of a .006 tighter group!
 
Don
The biggest problem in shooting really tight groups is the shooter , I would agree , I just like to make everything as exact as possible to cut down on my excuses . The wind is what I use most , makes me laugh . When things get too serious it takes the fun out of shooting . I enjoy reloading as much as shooting , even cleaning .
 
I take the safe route and never use virgin cases at a match or in testing and let the primer deburr the flash hole on the first firing.
Click to expand...

I think my first question would be , what is a bur , and what kind of deburring your primer can do ?

These are what I consider burs . I cut down these cases to look for burs when posting in another thread where guess who said there's no such thing in cases . Found these in less then ten try's so 30% of the cases I looked at had burs in them .

EBAX6Z.jpg


The next question would be can these effect ignition ? Not sure but would think not . So then the next question would be are there ever any "hanging chads" sort-a-speak left in or blocking the flash holes in new brass . I've never came across anything like that to date but I mostly shoot once fired brass so maybe all my cases had the first firing push that chad out of the way ???

Sometimes I debur and other times I don't . Like I've said before ,I'm not sure I can shoot well enough to notice if it matters . That and the fact I tested how I hold the rifle to my shoulder effect SD/ES so unless the gun is in a machine vise I'll ever likely know how well "my" case prep works . Maybe bench rest guys have a better ability to see these things do to the fact they don't actually hold there firearm resulting in a more consistent recoil pulse from shot to shot when the rifle is fired .
 
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