Shot a load i had previously worked up for my 308 this weekend. 150gr NBT, 46.5 Varget, CCI Magnum, Rem Case. Sub .75 MOA averaging 2840 out of a 20" barrel. No sticky bolt, mild recoil, but the spent primers seem to have lost the curvature of the original shape. Im guessing this is the flattened primer pressure sign, any ideas?

model7LSS, I have always 'read' primers but no-one will say anything about the subject. I hope you have a better response. But, FWIIW, a primer that shows some residual 'roundness' at the edges of both the primer and the firing pin indent, is not an overload. It does, of course, depend on the 'hardness' of the primer. One test is to use a known soft primer but that would likely mean a different pressure anyway (and will likely not properly ignite a charge that requires a magnum primer). I am sure Hot Core will give some advise here.

All primers will flatten to a degree when fired, so it doesnt necessarily mean that the load is overpressured. Magnum primers aren't needed in the .308, but if you worked up the load with them thats fine.

Look at them when you deprime them from the case. If the edge is still rounded a little then that is just normal working pressure. If it looks like a knife edge, thats too much.

I don't put too much stock in primer appearance anymore because once they give a sign of overpressure, you are way out of the ballpark.

Personally, I have found that if you stay within the max charges and watch the chronograph that most pressure problems are easy to avoid.

I don't use just one pressure sign; the primer is just part of it.

Just going by hour sub 0.75 MOA average, I would say the pressure is fine. When pressure becomes excessive, the vast majority of the time, groups open up and I doubt you'd be getting 0.75 MOA groups.

Pressure signs also vary with the kind of gun you're shooting. A break open shingle shot rifle will be different than a bolt action rifle; a revolver will be different than a semiauto, etc. Also, pressure signs in different cartridges vary. In some you'll get a pierced or leaking primer before you get a flattened primer which is a sure sign of excessive pressure.

quote:

Im guessing this is the flattened primer pressure sign, any ideas?

I'm one that looks at the primers......and I still believe they tell a part of the story..... maybe not the whole story but part of it.....if you can post a photo of the case head and primer it would help a lot.

If there's someone that can check your head space that too helps us!

primers do indicate pressure signs, most of the ones I seen show a pearcing or little black streaks on the brass away from the edge of the pocket or a soot aroud the pocket.
With a mag primer and 46.5 grs oF varget you are probably at about max pressure 58000P to 60000P. 2840 is a healthy velocity for that bullet weight in a 20" barrel. my best results with the 308 was with H380 168gr sierra at about 2700 to 2800f/s 24" barrel mauser action . some 5 shot groups were in the low.5's..
Dave

I know that magnums arent necessary but I cannot find any standard primers here. I dont think headspace is an issue, the gun is a custom made by a very good smith, only around 200 rds down the tube. I did change brass from Hornady to RP this go round. I havent even thought about looking at the hornady brass yet. I will look at them and see if I see any of the same.

quote:

Originally posted by model7LSS:
I know that magnums arent necessary but I cannot find any standard primers here.
Magnum primers probably are not an issue.....agreed

I dont think headspace is an issue, the gun is a custom made by a very good smith, only around 200 rds down the tube. it's probably minimal.....but you don't know unless it's confirmed

I did change brass from Hornady to RP this go round. I havent even thought about looking at the hornady brass yet. I will look at them and see if I see any of the same.

From what you have posted it seems you're fine and the load is fine.....but a photo of the case head would be great.

will get one up as soon as i get out of class

okay, dont really want to go through the trouble of setting up photobucket to post a crappy photograph, so i decapped one spent round and the primer has a significant "flange" at the base. The same loads in Hornady brass with standard primers also have this marking, even load with lesser powder charges. Thoughts?

take one of your fired cases and reload it again but don't run it all the way into the FL die.....leave it about 1/16" away from the base of the die....repeat the firing and see if the primer looks the same.....essentially this eliminates any possibility of headspace being an issue!

Primers do have the ability to indicate when a specific Load is too hot as described by "hivelosity". If Blow-By happens on the first Load in a new Case, I would consider it a serious Over Load. If Blow-By happened on the 3-xx reload, I would still consider it too hot, but some folks don't.

And Vapo is on a good track by making sure it is not a Headspace issue. Of course, proper Die Adjustment to P-FLR will eliminate that - unless - he Hunts Dangerous Game country and then all the cases which go Hunting should be Full Length Resized.

The question would not have arisen if CHE, GE, and PRE were being used.

hotcore can you elaborate on the che ge pre?
I have seen references to this but the consept evades.
thanks Dave

Hey Hivelosity, CHE & GE allows anyone to see how much the Case Head is or is not expanding, as you are Developing Loads. But, there are some "tricks" to doing it so the data is useful. A person Developing Loads for any Wildcat would be at a serious disadvantage not to know how to use these Methods. And of course I consider the same is true for all cartridges.

Neither CHE or GE are useful on the old Low Pressure Cartridges where any Case Head or Groove Expansion would be beyond the SAAMI MAX. However, good old, never fail PRE works on the old ones as well as the newer cartridges.

If the link is still working, you should find all the info needed right here.

It is important that those Instructions are followed exactly as written.

Best of luck to you.

quote:

those Instructions are followed exactly as written

Regards CHE; just be advised that if you follow "those Instructions are followed exactly as written" you may very well be into proof load pressures before you get any measurement of case head expansion. This has been proven many times when comparing CHE against proper pressure measurement. Hot Core will come back back with his usual drival about modern pressure measurements (Hot Core; CHE was disproven in "labs" also).

I'm not telling you to not give CHE a whirl as I used it for years until I found out better. I foundmy "safe" CHE developed loads were over SAAMI max MAPs when I aquired the equipment to measure pressures. Many have for some time been writing the CHE isn't reliable. If you use CHE I advise to use new cases and take the measurement after just one firing. Repeated use of the same case can even askew the results more. The new case use was as originally developed. I don't know where Hot Core came up with the use of once or twice fired cases. Just be careful and pay attention to what the other signs of pressure are telling you along with the SD and ES of the chronograph. If the average vlocity is above what is expected then that generally is telling you something about pressure also.

Watch all the pressure signs. Your load with Varget is not a max load. The Palma recommended load with the 155 gr Palma bullets is 48.5 gr Varget. In my .308W target rifle 45 gr Varget under a 175 gr MK generates 49,200 psi(M43). I've shot lots of the 48.5 gr Palma loads with nary a pressure sign. You may be sizing the cases to much and have a self induced headspace problem as suggested. Look there also.

Larry Gibson

Hey Hivelosity or anyone else who is interested, If you have a question about CHE, GE or PRE, send me a PM and we can discuss it without having to wade through all of the doughnut-eating radar-running, totally incorrect

I work up a load to the threshold of short brass life, and then back off a safety margin, ala Vernon Speer 1956.

Short brass life in 308 [or any other 1889 7.65x53mm case head with large Boxer primer pocket] is the primer pocket getting loose.

If you have case mouths that split before primer pockets get loose, get a sizer die with larger neck, get a chamber with a smaller neck, get better brass, or anneal your case necks.

If you have primers piercing before pockets get loose with the .308, you have other problems that need to be fixed. You need to get a round nosed firing pin with proper protrusion or stop using pistol primers. If your firing pin hole is .2", you need to get the hole bushed or get another rifle.

If you have case head separation before loose primer pockets in a .308, you have other problems that need fixing. Headspace, brass quality, and action stretching are some things to look at. Only push the case shoulder back with the sizer die .001", not .100".

Firing the same 5 cases 5 times and looking for a pocket that takes less than half the original force to insert a primer would be a good test if you can afford a technician to order around.

A much easier test is to measure extractor grooves outside diameters before and after firing with dial calipers. A .010" increase may be associated with a primer falling out on the first firing, but .001" change can easily be resolved.

Spin the case in the calipers before and after firing. The initial run out is very low, but a swollen case head is often asymmetrical. A .001" increase in all cases is above the threshold. A .001" increase in 2 of 10 cases is right at the threshold for reducing a safety margin.

Speer reduced by 6% powder charge.
2% is plenty for me with well controlled handloads for the same rifle, but jammed into the lands vs just off the lands can spike the pressure equivalent to 2.5 gr, which is your whole 6% error budget right there.


Just like global warming fear mongers have Al Gore, pressure fear mongers have Denton Bramwell. If you belong to Denton's cult, you fear pressure, and worship it by measuring your chamber with transducer or strain gauge, and kludge your way to SAAMI registrations in psi capriciously assigned to that cartridge. They pray to psi by flaming Hot Core.

Hot Core [his real name is Glenn] has his own pre che cult of brass measuring.

I am trying to start my own cult of handloaders that think of the weak link as brass life from loose primer pockets, work up to that threshold and back off a safety margin. I have no followers, just other guys that already do it the same way.

tnekkcc

Glad to see you've at least backed off from "load 'em till the primer pocket blows, then back off" method.

Many of us know the difference between fear and respect. Obviously some of you don't. I do not fear pressure, I respect it. I've several cartridges that I regularly load beyond SAAMI MAPs. I know what pressures I am getting and do not have to guess by taking the brass cases to "loose primer pockets" first. Not sure how Denton got into this unless you're still hung up on that fetish.

Your note of jealousy and envy of those who can measure pressures and use due caution is well noted.

BTW tnekkcc, The Jack O'conner article in an older Speer manual is a much better guide for loading for your rifle than going to the extreme of loose primer pockets. You might want to read that one.

Hot Core came through with his usual drival as I surmised he would.

Larry Gibson

quote:

Originally posted by Larry Gibson:
tnekkcc

Glad to see you've at least backed off from "load 'em till the primer pocket blows, then back off" method.
Many of us know the difference between fear and respect. Obviously some of you don't. I do not fear pressure, I respect it. I've several cartridges that I regularly load beyond SAAMI MAPs. I know what pressures I am getting and do not have to guess by taking the brass cases to "loose primer pockets" first. Not sure how Denton got into this unless you're still hung up on that fetish.
Your note of jealousy and envy of those who can measure pressures and use due caution is well noted.

BTW tnekkcc, The Jack O'conner article in an older Speer manual is a much better guide for loading for your rifle than going to the extreme of loose primer pockets. You might want to read that one.
Hot Core came through with his usual drival as I surmised he would.

Larry Gibson

Count the insults. All I can think is that fear and hate are driving those insults. I can pray for you.

Over the years at Accurate Reloading forum I have endured hundreds for flame wars between Denton Bramwell "Denton" measure pressure advocate and Glenn Rice "Hot Core" measure brass advocate.

I think they are both electrical engineers, as am I.

After that much arguing, it is a stylized debate.

I have my own flow chart:
1) If I were to sell ammo, I would measure pressure* and develop
loads to SAAMI registered pressures.
2) If I am loading for a gun that is weaker than the brass, like a revolver with .040" thick chamber walls and a rimmed case, just don't exceed max loads in load books, where pressure was measured.
3) If I am loading for a gun stronger than the brass, load up to the threshold of short brass life, and reduce by at least a safety margin to find the max load for my gun.

* With CEA-O6-250UW-350 strain gauges and AD8554 op amps in an instrumentation amplifier configuration, I can get great accuracy in measuring the strain on barrel steel locally.
Instrumentation amplifier - Wikipedia, the free encyclopedia
One problem I have is the precision of where the gauge is epoxied onto the barrel.
Another problem I have is that the barrel is not a uniform thickness thin wall long tube. It is an open ended tapered tube. That gets me into Roark's book on stress vs stain on open ended tubes:
Amazon.com: Roark's Formulas for Stress and Strain: Warren Young, Richard Budynas: Books
I think Denton buys amplifiers, and calls mine "home brew", but mine are more accurate. The inaccuracy is in the epoxy, position, thickness, and formula for tapered open ended barrels. Then there is the error of value used for Young's Modulus for steel in the barrel.
I have a friend who has by passed this, and gone to pressure receiver and transducers.
That still leaves errors for the handloader, in that it misses the individuality of the gun and the error of the pressure registered with SAAMI.

What does it all mean?
Those who are so afraid of the pressure that would change their brass, can follow load books, measure pressure with strain gauges, or measure pressure with transducers.
These individuals are including many errors, but let them live with those errors. It is their lives. Some of us have gone past the fear and have a more accurate and efficient system of reading the brass. We each pay our money and take our choices.

tnekkcc

"Count the insults. All I can think is that fear and hate are driving those insults. I can pray for you."

Now there's the classic "kettle calling the pot black"! Read your own posts. They are full of insults. All that is beside the point though. The point is that Strain gauges are proven to be reliable. Dr. Oehler has proven this with an extensive side by side test he conducted. While "reference ammuntion" is not necessary the users of such strain gauge systems use factory ammuntion as a "reference " of sorts. I have contacked both Federal and Winchester and they have given me the pressure that they measured (with their "lab" equipment under laboratory controlled conditions) the lot of ammuntion I was testing. They have done this several times. All of their measurements coincided with mine taking into consideration an offset for my production chambers and barrels vs their tightly spec'd test barrels. In other words, the M43s measurements were spot on. If you are an engineer as you state then you can appreciate that fact.

With CHE the reloader only assumes the cases he has give the same expantion that Hot Core uses for his "measurements". Problem is many cases have different expansion charactoristics and do not expand the same at high pressure. This has been proven over and over again by professional ballisticians. I recently proved it again and posted the results using purchased Winchester White box M193 .223 ammo. Both you and Hot Core seem to conveniently disregard such actual evidence and ffacts.

It was not an insult BTW; I do commend you on you're backing off of your previous "load 'em till the primer blows" postition. Perhaps your engineering background and education are coming into play.

Larry Gibson

Even if a stain gauge placement error, epoxy error, barrel taper error, Roark forumla error, Young's Modulus for steel estimation error, strain gauge error, amplifier error, sample and hold error, and SAMMI pressure choice error could all be over come and were perfect... you still would not have the brass used hardness and thickness optimized.

That is, if the strain gauge system were perfect, and it is terrible, it would still be an expensive, cumbersome, and inferior to just looking at the brass.

This understanding does not require education.
An inner city teen ager with some street smarts could understand that Oehler can take in some fools, but not that kid.

That is, it is down to common sense.
And to quote the old Satchmo, Louis Armstrong, "If you don't know, there ain't no way to tell ya."


Larry, face your fears. Overload all your guns until the primer falls out to show you have the brains to manage risk. Throw all Oehler gear in the trash. Go to the next level.

A definition of insanity is taking leave of the senses. Use your eyesight to look at the brass.

I am just across the water on South Mercer Island if you need help.

quote:

That is, if the strain gauge system were perfect, and it is terrible, it would still be an expensive, cumbersome, and inferior to just looking at the brass.

yup....it works for me!

BTW.....I could care less about SAAMI pressures in most cases!!!!

quote:

Larry, face your fears. Overload all your guns until the primer falls out to show you have the brains to manage risk. Throw all Oehler gear in the trash. Go to the next level.

Just when we thought you were "managing" you own intelligence. That's the way to do it alright, really intelligent.

Larry Gibson

Larry,
I feel your sarcasm.
Let it go.
You can do this.
You know your guns are strong.

tnekkcc

Not even if it was your face behind the bolt. One of us isn't stupid.

I'll hold your beer while you say, "thanks, you ain't gonna believe this sh*t, just watch!"

Larry Gibson

gentlemen please, enough with the insults to one another. Thank you for both of your replies to my question, I have furthered my knowledge on the subject substantially.

model7LSS

Relax please. Tnekkcc, Hot Core and I always have this type of conversation. It's no big deal. We'd actually all probably have a great time shooting together (not each other ). Hot Core and I would probably fight over the donuts while tnekkcc was pulling bullets in our ammo and adding more powder......just friendly chit chat you know!

Larry Gibson

quote:

gentlemen please, enough with the insults to one another. Thank you for both of your replies to my question, I have furthered my knowledge on the subject substantially.

quote:

.... Tnekkcc, Hot Core and I always have this type of conversation.

These three Good Folks (among others) are mine-fields of information! (Uhmm... mines of information).

thanks fellas, good to know. thanks for sparking some new thoughts and ideas.