flattened primers

[Darksith]

I have worked my way up to a load that flattens most primers, but some primers remain normal. The bolt never sticks, and I am 3 grains under max load. To go any higher is dangerous? What about shooting a load that flattens the primers but no sticky bolt? I fired 30 rounds @ 3 grains under, then I fired 1 round of 1 grain and 2 grains higher (1 under max). Still no sticky bolt, and the 1 grain over primer didn't flatten. Ive never had a flattened primer before, and I am shooting very good groups with the 3 grains under load even though it flattens the primer?

Also I am shooting some brass that has been fired lord only knows how many times...if the neck becomes to thin can it crack a bit? Had 1 shell do that today, figured it must be an old piece of brass from my uncle. It cracked along the length of the neck.

[RWNielsen]

I've had factory ammo (Win, 180g, .308) that flattened primers pretty good.
I had never loaded .308 before and wanted something to compare to. If they had been my loads I would have been concerned. Flattened primers are not a reliable method of determining whether a load is too hot. I get them all the time in .357 and .44 mag loads and I never exceed published data. I seems to have more to do with the materials of the primers themselves.

[Darksith]

so as long as I am under max load I should be fine to shoot it.

[burrhead]

“so as long as I am under max load I should be fine to shoot it.”

Maybe, maybe not. I have a Remington 722 in .308 that, using LC brass, shows serious pressure signs at about two grains under max with Varget and 150 gr. Sierra Pro Hunter bullets. Very sticky bolt, flat primers, etc. I know all about backing off when using LC brass and this gun proves the rule. Reloading manuals are guides, not gospel. Be careful out there.

[Malamute]

What burrhead said.

If you read your manual, not just "look up a load", they will repeatedly say that the combinations they came up with are only for those exact components, in that exact rifle, and the reason to reduce to a starting load and work up is your gun is different, and your compnents of choice are different, even a different lot of brass, same manufacturer, may be differnt than the last lot you bought, or what they used. "Maximum" loads are not gospel as valid in any other gun, or different primer, or different case, or different bullet, or even different lot of powder. Often things are close enough to make out without hazard, but thats the reason to start low and work up. It's quite possible to get an over pressure load that's not above the book max load. It's all about the particular combination in your particular gun. Even the next serial number gun off the production line can be different.

It sounds like you may be using a mix of differnt brass also? That can dramatically change pressures.

Are you measuring case head expansion as a pressure indicator?

[Darksith]

no I am not, but I will.

Flattened primers are only at best an indicator that I maybe approaching what I would consider to me a max load in my gun. Is that a good way of saying it? I have worked up this load, and some of the primers didn't flatten, but this is probably b/c of a few different variables like mixed brass, etc...I never once have had any sort of sticky bolt feeling, just flattened primers.

[Randy 1911]

Like said earlier, manuals are just a guide. In my rem 700 with 30-06 my most accurate loads are 1 grain undwer reccomended start.

[SL1]

the case is the weak part, and should fail before the gun unless there is something seriously wrong with the gun.

So, for modern bolt action guns, you can monitor the brass to make sure that you are not approaching a load that will make it fail. HOWEVER, you need to understand what you are measuring to do that appropriately. Brass work-hardens when it is deformed beyond where it springs-back to its original shape. So, pressure that slightly expands the case head on the first firing will harden the brass so that it won't expand again at the same pressure. In fact, it won't expand again until the pressure is SUBSTANTIALLY higher. SO, you shouldn't keep firing hotter and hotter loads IN THE SAME CASE and repeatedly look for case head expansion to exceed some arbitrary limit. There is a good write-up in Lee's "Modern Reloading" that gives some examples of what can happen.

Looking at case head expansion in a bunch of "mixed brass" cases of unknown and probably varied histories won't tell you much, if anything. The method only works if you use new brass or once fired brass from the same lot of factory ammo.

Cracked case NECKS are usually an indication that the cases have been reloaded several times. The expansion and resizing cycle has work-hardened the necks to the point where they have become brittle enough to crack instead of stretch. Failures of that type are not dangerous, but should tell you to either anneal the case necks or scrap the remaining case in that batch with the same history.

The dangerous types of case failure occur in the case head or in the wall between the head and the pressure-ring, where the case does not expand enough to seal the chamber so that gas can escape back toward YOU. The most common problem is this region is "case head separation", which is caused by the case wall repeatedly stretching and becoming too brittle just behind the pressure ring. Eventually, a circumferential crack develops in the case wall and the case separates into two pieces, allowing a LOT of gas to escape back towards the bolt. The cracking typically happens in one firing after several reloads, and MAY be preceded by the appearance of a bright ring around the case where the separation is about to occur. But, it is easy to obscure the ring with dirt or too much polishing, so that isn't a reliable indicator. The best way to test for incipient case head separation is to use a straightened paperclip with a small 90° hook in the end to feel the inside wall of the case for a groove. If you THINK you feel one, section the case and look at it. Initially, you will probably section some cases that have little or even no real groove in them. But, that will give you the way to "calibrate" yourself to understand what you are feeling with the paperclip.

As for flattening primers in SOME cases, it is hard to offer any useful comments without knowing how dissimilar those case might be, or even what cartridge you are loading with what powder. Two grains of powder is a lot in a .221 Fireball, but not so much in a .378 Weatherby Magnum. And, case internal capacity variations can be quite large among cases from different manufacturers, amounting to as much as 2 grains in the .30-'06 family of case.

SL1

[mehavey]

....a load that flattens most primers, but some primers remain normal. The bolt never sticks, and I am 3 grains under max load.

It might also be that some cases are being sized more than others -- which is always possible depending on amount of case lube on individual cases, die adjustment and amount of reloading press "spring". If so, the oversized cases allow the primer to back out slightly before the case head stretches/slams back into the bolt face -- reseating the protruding primer and then flattening it in the process. This would give you some "normal" primers and some "flattened" ones for the same powder charge.

Before I say that "3 grains under" should not ordinarily give you pressure problems, would you share the loading info?

- Rifle
- Cartridge
- Case manufacturer (BTW - don't mix cases and expect consistancy)
- Bullet (Type/Wt/Manufacturer)
- Powder (Type/Wt/Manufacturer)
- Reloading Dies (Manufacturer)
- Press (Type/Manufacturer)
- Case Lube (and the technique used in lubing cases as you go)

[GP100man]

chronograph em !!! The manual states pressures to fps , then compare your results .

Just too many variables to follow manuals to the letter , there more like guide lines & this is a perfect example why we all should start at starting loads !!!!

[alloy]

What I don't understand is how the same primer can flatten just as much in a relatively low pressure 38 special or a high pressure 40 cal. Obviously the pressures are so far removed from a normal comparison between the two.
Insight?

[Jim243]

Two things came to mind while reading your post. The first is that if your cartrage is under the min for the load, you could have an over pressure load due to smaller amount of powder in the case and the more difficulty in starting the bullet down the barrel.

The second was that your case may not be sized correctly and the shoulder is set back too much, so you are experiencing too much headspace on these cases. I would suggest getting a sizing gauge to check this out.

Without knowing what caliber, powder, OAL and primers you are using, it is near imposible to give any recommendations as to what to do.

Thanks
Jim

[GP100man]

head space does play a role in primer deformation, as the FP drives the case forward then ignition takes place causing the primer to back out the pressure drivin the case head back under pressure catchin & crimpin the primer in the bevel giving the apperance of a flattened primer .

& all brass used in the manufacture of primers , different lots , Different thicknesses , all within specs ??? how close to either end affects the "picture perfect" primer deformation !!!

I measure case heads for pressure signs also , more so than primers .

I have a box of 357 magnum factory I chronoed & the primers are completely flat , but the case heads did`nt move at all !!!

[snuffy]

Not much to add to the above comments. Except that I NEVER pay any attention to primer appearance! WHY? Because they are NOT good indicators of pressure. For ALL the above reasons given. You might just as well read tea leaves, or palm readings to predict pressures.

When I'm working up loads, I use a target, AND a chronograph to tell me what's going on inside the shell. That's called internal ballistics.

I also notice bolt lift when working with a bolt rifle. Or extraction effort in a single shot or revolver.

Case head expansion is tricky to do UNLESS you have a micrometer capable of measuring .0001 increments, AND know how to use it. Forget dial calipers or digital anything!

START OVER! With new cases, or cases from factory ammo fired in that rifle. Then you're dealing with a level playing field, you'll be able to tell what's going on.

[GeauxTide]

I've followed Ken Waters practice of head measurement to determine maximum loads. For instance, the head measurement of the 308 and '06 family is .473. If your load produces .005 over that, it is maximum. Works like a charm, and I usually get primer signs.

[GroovyMike]

IMHO - if the primers flatten then pressure is too high.

[wncchester]

Probably 99% of "flat" primers is due to reloader created excessive headspace by excessive resizing and setting the shoulders back too far.

Use a neck die OR back your FL sizer up by 1/8th turn (about 9 thou). See if that doesn't fix it, immediately.

Anyone seeing 5 thou of head expansion is VASTLY over safe pressure limits! One tenth of that figure is the commonly accepted limit.

[HiBC]

I initially was going to comment it is more likely this is about excessive head clearance.I agree with what has been said.I am going to tie some good posts together.
The brass case limits the pressure to the chamber.If it fails,the gas escapes.It can wreak havock with your rifle,or pehaps your face.A subtle damage is gas cutting.It works like a cutting torch to erode steel.Anyway,case failure under pressure is very bad.

When ignition occurs,the firing pin has driven the case forward.The the case obturates,expands and seals.The thinner parts of the case,forward,expand first.The brass grips the chamber walls.PO Ackley shows this definitively by removing the locking bars from a 94 win and firing it in 30-30 AI.It stayed closed.So the forward part of the case stays forward.
Gas pressure then blows the primer back to the bolt face.Unsupported,the protruding primer expands.Then,at the chamber mouth,the brass is unsupported.It has nothing to grip.This is where the case stretch occurs as the case head is blown back to the bolt face.Along the way,the primer gets flattened as it is re-seated.Do a search for Varmint Al and brass stretching finite element analysis and see what you find.

Now,you could have a rifle with excessive headspace.It is also possible to create a situation at the reloading press that will have the same result as excessive headspace.A die has to size small enough to have clearance in the tightest factory chamber.Remember the die works with the shellholder.What brand is the shellholder?Tolerances accumulate.As that finite element analysis shows,.006 head clearance will make a stretch ring.One part of being safe is with recommended pressures.The other part is sound brass.A case failure at safe pressure is still bad.

The best way is to have and use tools that tell you how much setback you get as you size your case so that you can control it.
There are attachments for caliper,RCBS precision mics,Wilson,Lyman,Forster,Dillon case gages,etc.

Good luck,wear shooting glasses.

[snuffy]

If your load produces .005 over that, it is maximum. Works like a charm, and I usually get primer signs.

Anyone seeing 5 thou of head expansion is VASTLY over safe pressure limits! One tenth of that figure is the commonly accepted limit.

I think GeauxTide meant .0005. Or 5 TEN thousandths. Even that is a lot. Usually the case head expansion is read on a factory round,(or how ever many you fired), then your handloads should measure the same. Because the factories usually load to max pressure, that gives you an idea of what is maximum for that cartridge.

If you exceed what a factory loaded cartridge case head expansion reads, you will start to notice the primer pockets getting loose.

IMHO - if the primers flatten then pressure is too high.

As I stated, primer appearance means almost nothing. That right there IS just your humble opinion. Read the whole thread!

[GeauxTide]

Thanks, Snuffy. I didn't check my zeros.

[wncchester]

"Thanks, Snuffy. I didn't check my zeros."

I did.

[SL1]

It is pretty easy to delude yourself into a false sense of safety, even if you realize that you need to deal with tenths of thousandths, not thousandths of an inch.

I hope folks reading these posts don't try it UNLESS they take the time to research it and learn about it by making those measurements on both factory loads and the handloads that the have worked-up WITHOUT counting on the case head measurements.

For starters, please realize that you are NOT looking for a maximum case head diameter, you are looking for a CHANGE in case head diameter. And, you can't look for that change in just any old case. You need to realize that the same pressure will make DIFFERENT levels of change, depending on what pressures the case has previously experienced.

SL1

[Doodlebugger45]

The other day I was decapping a bunch of .243 brass that I had accumulated prior to starting reloading for that cartridge. All of it was once-fired factory ammo from a variety of makers. It was amazing to see the difference between the primers. They were all consistent among a given load (I had kept the fired cases in the original factory boxes), but they varied from no flattening at all to a heap of flattening. I suspect that primer flattening has as much to do with the hardness of the primers as it does with the rest of the load.

I read Clark's experiments with extremely overpressured loads and his observations regarding measuring the diameter of the extractor groove. It does appear that there is a consistent increase in that measurement just before the case fails. But that expansion is pretty small and you have to be very meticulous in measuring the same case before and after firing, so it's not a practical method for me. What I got out of his experiments is that new brass and new rifles are vastly overengineered compared to the stated max pressures. However, I sure don't want to be the exception who has a weaker action or a weak case.

From a practical standpoint, I rely mostly on the feel of the bolt when I extract the shell. If weaker charges were extracting OK, then all of a sudden a heavier charge feels sticky, I figure I've gone too far.

[mehavey]

After many years and many calibers/cartridges, my lowly AR has taught me that neither primer "look" nor head expansion is a reliable indicator of borderline chamber pressure.

Head expansion on a 223 at even factory operating pressures, 52-55k, is a fact of life -- resulting in primer pocket expansion/discards after 5-6 reloads no matter what. Hornady4th-Speer/12th seem to agree, saying that in general terms, case head expansion between .0003 and .0005 is typically the result of chamber pressures in the 50,000 psi range. Some specific 243 data is presented here that says 1-2 thousands (permanent/residual plastic deformation) is normal.

http://www.google.com/imgres?imgurl=...:1%26prmd%3Ddf

Larger-diameter head cases can take this w/o squashing the primer pockets irrevocably open far longer than the itsy-bitsy 223 can. For that reason, the AR is a good teacher of pressure effects.

And unless you are supremely careful on resizing--either neck sizing on bolts and a measured 0.002" bump on autoloaders--the primers may/may not be telling you anything, particularly when relative primer cup "softness" varies considerably between manufacturers by design.

Folks have asked earlier whether a chronograph is required for safe loading when bumping anywhere near max published loads. It may not be required,... but I sure feels more comfortable when I gots one..