Cleaning primer pockets

[Mako]

Mr engineer Mako, riddle me this. Elmer Keith wrote that primer pockets flow BOTH directions and I have found this to be true, albeit too late once. Is there a scientific explanation for this?  

Kid,
I don't recall that exact statement or the context, can you elaborate?  I don't know what "both ways" means.

The pocket and the head can definitely flow in high pressure cases.  This is the exact reason you protect the base if you anneal the mouth, neck and shoulder on brass.  

With standard cartridge brass which has a ratio of Copper to Zinc of 70:30 the yield strength radically changes between the Annealed and "Full Hard" conditions.  Brass work hardens and the heads are considered to be at the Full Hard for analysis purposes.



There is actually a condition softer than annealed which is called "Dead Soft" and a harder condition called "Extra Hard" for cartridge brass, but these are the values commonly used and the values accepted by SAAMI.  The flow as we call it is when we exceed the elastic limits and get in the plastic deformation range.  Brass is a great material for cartridges because it has a large difference between the Full hard and Annealed strengths and is very easy to manipulate with relatively low heat after fabrication.  

The steel cases you see on former "Eastern Block" and Chinese ammunition is a poor choice for BP and really isn't that good for nitrocellulose.  It works "once" in high pressure applications, but weapons using it get noticeably dirtier in the chambers and actions.  The Russian designs handle it because they are designed with clearances our Western weapons designers consider loose.  People using Russian steel case 5.56 ammo in an M16 find they have problems in sustained high rates of fire.

Israel played with steel cases but found they would work with some Galils but not reliably with M16s, M4s, Minimis or the M249 variant. They didn't work in all Galils because the chamber specs are tighter on the Galil than the parent Kalashnikov design.  The Dragunov has an accuracy worse than than 2 MOA with the steel cases.  They use brass or special thin neck steel cases for their designated "sniper rounds."  The PKM GP machine gun can use it because it has a rimmed design, if you've ever wondered why they stuck with the rimmed case instead of converting to a rimless design it has to do with the development of the steel case.  They use annealed cases and the external rim can be locally hardened to prevent the extractor tearing through the case during extraction.  This is the reverse of how we make a brass case.

The Aluminum cases you see with the CCI Blazer cases are "single use" cases as well because they basically have very little spring back.  It obturates better than steel but then that's it.  The material work hardens on firing and the tensile strength is radically compromised and develops microcracks.  If you've ever used the ammo you will find it is usually harder to extract than brass cases.  Sometimes I lend guns to friends for CAS shooting and they want to buy ammo, I tell them to get Blazer if it is the cheapest but then I allow them to shoot it in the revolvers, but I give them handloads for the rifle and trade them out for the blazer ammo and save it for loaner or plinking ammo for pistols.  I don't like the pointier noses on the bullets or the sticky cases in the rifle, you can deal with a sticky case in the pistol at the unloading table after the stage.

If you can explain what you mean I can probably explain it.

~Mako

[Montana Slim]

An old saw: what do engineers & accountants use for birth control?     Their personalities. 

Coincidently, some years ago I gave my son a vintage Iowa Lotto T-shirt that said "Call-me-Lucky" . 

As far as primer pocket cleanliness...I have not given any of my (thousands) of cartridge cases a primer-pocket "cleansing".
...and, some of my 44-40 BP brass dates to the 1930's.

Steel cartridge cases for the M16?? well, that has been solved for some time now......currently, the science kids are palying with polymers at the moment....I predict polymer bodies and necks, and steel heads....one day...not necessarily practical for mass production in my lifetime, though.

Slim

[Mako]

...Steel cartridge cases for the M16?? well, that has been solved for some time now......

Sure you can buy them by the case and much cheaper than brass cases, but the problem is not solved...  Steel case 5.56 ammunition is all over the internet.

If the problems were solved , we would be using them.  Steel cases are also lighter than brass cases, it would have been jumped on a long time ago if the functional issues had been solved.  Brass cases act as heat sinks and help remove some of the heat from the chamber, brass is more lubricious.   Consider this, copper is a strategic material and they would have already redirected that resource if steel small arms ammunition for our weapons systems was as reliable.  Steel is cheap and plentiful copper is not. The M4 systems already have borderline issues with reliability, they would never introduce steel cases with the current impinging gas design.

A lot of the higher caliber casings are steel or even aluminum.  But I know for a fact steel failed miserably with 5.56 tests.  I mentioned the Israelis because I worked on the project with IMI .  We (the Pentagon) were actually buying 5.56, 7.62 and .50 cal  ammunition from IMI as late as 2005 because our arsenals and contracted companies couldn't keep up with the demand in Afghanistan alone.  We were using almost 2 BILLION rounds a year, we were looking for alternatives anywhere.  As a side issue Israel wanted steel because of cost and weight and they consider it a waste of an expensive resource, the Israelis are relatively pragmatic.  American programs have evaluated steel cases for small arms and the 5.56 always comes up short.  The Army doesn't buy into the Navy Research, so they waste more of our money and go through their bureaucratic processes just rehashing in a decade what we accomplished in a year.

currently, the science kids are palying with polymers at the moment....I predict polymer bodies and necks, and steel heads....one day...not necessarily practical for mass production in my lifetime, though.

They have been doing that since the '70s...The latest one is the NATEC cartridge.  Except the only NATEC 5.56 case to date that works still has a brass head.  The steel still isn't reliable.

I was actually  involved with testing the NATEC cartridges made by amtech until until the JSSAP jumped in and got them to sign a CRADA with the army, then it went downhill from there.  It has gone into the great bog of stopping progress called the JSSAP, and the black hole ARDEC.  Now they have rolled it into their lightweight weapons program.  Wooooo hoooo! How many years have they been beating that horse?

You're right about it being not in your lifetime, not with that bunch at the controls.  Cement boots for everyone!!!!

~Mako

[Fox Creek Kid]

Mako, by that I mean the brass can flow forward, making the pocket deeper and flow backwards as well, making the pocket shorter. I have pondered this in the past and the only comparison I can come up with is that of case stretching. I have noticed that some rifle cases will remain the same length for several shots and then "boom" they are several thousandths longer!! This is what I believe happened to me after uniforming some pistol primer pockets once. These were older cases that had been shot several times (.44 Colt). I uniformed them and then fired them and they worked great. I then tumbled and the next time I had countless misfires as the primers sat too deep. No, I did not "gorilla' the primers into place as I use a Lee hand tool. I thought about this and remembered Elmer Keith writing about it and confirmed it with a benchrest buddy who is a "guru." Perhaps by uniforming them I "stress relieved" the pocket, so to speak, and allowed metal to flow in whatever direction it wanted to go. All I know is that it happened.

[Mako]

Kid,
I don't know.  Every simulation I have ever run or read about shows the web flowing back into the case which lengthens the pocket.

I addition the pocket get "looser" from two things happening.

• First, the diameter is increased from the pressure on the walls by the pressure coming back through the flash hole and the primer expanding against the walls.  
• The second is from the base collapsing and deforming from the rear thrust.  The case is almost always not "fully" supported at the rear.  There is often a lead in and even with full chambers there is usually a relief for the rim.

I already have a .25-20 Win case so I'll show you what an FEA plot of strain and displacement looks like with a 20,000 psi load.  

The Case


I have loaded entire volume of case including the primer pocket with 20,000 psi of pressure.  The case is constrained on the entire chamber area and the base of the case, the case mouth is not constrained on the front (this is why the neck grows).



This is the  displacement plot.  Note the actual displacement is VERY exaggerated to allow you to see the displacement gradients.




This is the strain plot, note there is a ring where the wall meets the web that has translated forward, thus thinning the case.  Everything else is to the rear or out at the rim.  Those of you that have shot a lot of high pressure cartridges will note the ring at the wall/web interface is where your cases thin and ultimately fail (that is using brass that get the shoulders forward periodically re-annealed and if the necks don't split first).


This is the final displacement under load shown in inches.  Note the mouth of the case has moved forward .002" and the bottom of the flash hole has moved forward .0216".  I used a discreet separation of the gradients to show forward and rearward movement.  Note the shoulder area material has translated forward as well.[/size]


Remember this is at the peak pressure.  The case will spring back except in the areas it has exceeded the elastic limits.  In those areas it will begin to flow.  Repeated firings will continue to flow the brass until we get long necks and distorted primer pockets.

A couple of more explanations, remember even though the bottom opening of the flash hole has displaced .021" that is the cumulative displacement of the entire face,  the entire area at the hole is not deformed .021", it is just at the end of a structure being displaced up.  Think of a 2X4 stud as an example.  If you anchor one end of an 8 foot stud a child can push on the cantilevered end and bend it. The end displaced is just the result of thousands of small displacements along the length of the stud.  Shorten the stud to 1 foot and the same child can't bend it to the same displacement.   Since the flash hole is at the center of the feature it can be displaced and it will spring back, but there is some plastic deformation.

But... the growth of the neck along the axis isn't like a lever arm. it is a columnar displacement.  The shoulder area will pull back but the area you see as going from grey blue to the end of the case mouthhas displaced through the material.  Think of the 2X4 again, if you forced it to grow 1 foot in length it's not going to spring back like bending it to the side.  

The actual neck doesn't spring back very much along the axis direction.  The .002" is not the actual stretch, it is the displacement which includes the shoulders (notice the shoulders just thin with material going forward and backwards) and all of the areas you see as going backwards.  The mouth gets pulled back, but there is growth in that neck area shown as grey blue running to the light green blue right at the mouth.  I couldn't tell you what the actual stretch in the neck area is without isolating the neck and running a much more complicated analysis.  But we all know what the result is, it grows slightly with each shot.

~Mako

[wildman1]

Well then, that certainly clarifies that whole matter for me. And the pictures showed up this time. I thank you profusely Mako. WM

[Dick Dastardly]

When I feel the need to clean primer pockets, I remove the primers and tumble the brass in DD Ceramic Porcelain media.  Cleans 'em along with the brass.

QED

DD-DLoS

[wildman1]

DD, couldn't find that stuff on your website. WM

[Noz]

http://www.biglube.com/BulletMolds.aspx?ItemID=2615f5ab-5224-4bd3-a6db-aed6175c2fb0

[wildman1]

That http address does not work. WM

[Paladin UK]

Fer WM............
I think this is the page

http://www.biglube.com/BulletMolds.aspx?ItemID=2615f5ab-5224-4bd3-a6db-aed6175c2fb0&Quantity=1

Paladin (What hopes he`s helped ) UK

[litl rooster]

that one didn't work either

[Dick Dastardly]

Howdy Rooster,

http://www.biglube.com/BulletMolds.aspx?ItemID=2615f5ab-5224-4bd3-a6db-aed6175c2fb0

That's the URL I coppied off the firefox browser bar.  The CP media kits are in the Bullet Extras drop down menu.  Go to http://www.biglube.com and click on the bullet extras line.  A drop down menu should appear.  Click on the Ceramic Porcelain brass cleaning kits and that page should open.

Let me know if that works please.  My web master has been moving and there may be a lapse in service.

Thanks,

Dick

[litl rooster]

The website link did the URL did not

[Jefro]

Let me know if that works please.  My web master has been moving and there may be a lapse in servic

Worked fer me


Jefro

[Steel Horse Bailey]

The link doesn't work for me, either.

Not a problem, I just thought I'd try.

[wildman1]

url did not work but the web address did, thanks DD, much appreciated.    WM

[will52100]

Post date is getting a little old, but since this post is what led me to stainless steel media I thought I'd give a report.  Got it in today, didn't use the lemon powdered detergent or add any TSTP, just a little lemon juice and Dawn to see how well it'd do without the fancy chemicals.  4 hours and my 7.62 nato brass came out great, and best part was dumped everything in the cheap plastic rotary separator, filled the bottom half with water and a few cranks and all the SS media was in the bottom of the separator and all the brass was empty of the pins. Primer pockets were perfect, inside of the cases were supper clean too.

Now I dearly love my ceramic media, but will never again use it for 30 cal. bottle necked cartridges, too big of a PITA to get it out of the bottle neck.  I may give my 44's and 45's a test run with the SS media and see how it likes black powder.  Will know more when I get back from Korea this time.  I rinsed the SS media out and drained most of the water off, now to see if it rust while I'm gone.  A big help getting it all out of my tumbler was a plastic bag and a rare earth magnet.  Not sure what alloy it is, but it will stick to a magnet.

[Steel Horse Bailey]

When you say you got super results, do you mean perfectly clean ...

or perfectly clean AND shiny - as if polished in corn cob with polish compound/liquid.

The pictures on the SS media show that their brass is not only thoroughly clean, but shiny as if polished as well.

That has been my only real complaint of the medias I've tried.  They get my cases clean, but I have to then polish them as of old with a polish cycle.  Is this new brass look necessary for good BP and Smokeyless "hygiene" shooting?  Certainly not.  But it's what I have come to be used to, so that's what I'd like.  I've been cleaning with walnut or corn cob and mineral spirits/paint thinner then polishing with corn cob and liquid polish for nearly 25 years now (I've gone 'thru 5 vibratory shakers of different manufacturers and 2 Dillons over the years) and I have grown used to having rounds that look like factory when finished!  I KNOW it really doesn't make my rounds shoot any better, but I like it.


Will the SS rods clean AND polish in my Thumlers Tumbler Model B?  (Which works VERY well to clean using corn cob and amazingly clean with ceramic.)

As to the magnet, not all stainless is NON-magnetic.  Put that magnet up to your typical Ruger, S&W, Taurus, etc.  Some parts will be magnetic, some won't.  There are dozens of SS alloys.  By the way, Will, I wouldn't leave that SS rods media immersed in water for a typical 13 month tour to Korea, but I am ONLY assuming that your "Will know more when I get back from Korea this time" comment refers to a Military "visit."

But that's just me ...

YMMV

[will52100]

The brass came out nice and shinny and clean, but if I'd put a little TSTP in it it'd been brighter.  As long as the brass is clean I don't worry too much about the shine, because no mater how shinny I get it, when the brass dries it dulls a bit.  Most times after it's dry I'll run a short cycle through the vibratory tumbler then seal in zip lock bags.  I wish I could figure a way to keep the water from marking or lightly tarnishing the cases, but haven't figured that out yet.  Come closer by letting it dry on the tailgate of my truck in the middle of the day.  Of course I have had nice and shinny brass tarnish just from sitting on the bench.  I mainly wanted to try them to see if it would work OK with my bottle neck rifle cases.

I get slightly faster and better results from the ceramic, and ceramic works awesome on my straight walled cases, but anything with a bottle neck or base big enough for it to get sideways will jam up in the case.  We'll see when I get back in how the pins work on my 44's and 45's and black powder fouling.

Being magnetic I was referring to the possibility that the SS pins are martensitic stainless and possibly more prone to rust.  The lower the chromium content the easier the steel will rust, but with other alloy elements gives it the ability to be hardened through heat treating.  Being magnetic though makes it easy not to loose pins.

I'll be gone for a little over 5 weeks, I am working over there in the ship yard on a drill ship.  My deployment days are behind me, time for someone younger and in better shape to hump an alice pack.