Flattened primers 357

[PowerPistol]

Why would I be seeing flattened primers in a 357 with 8.0 grains of Power Pistol with a 158 grain JHP / JSP ?
Depending on bullet ( XTP, Zero, Nosler), it chronos between 1170 and 1200 FPS. I am seeing flattened primers with all of them. No other signs of pressure. Should I be concerned?

PP

[SIGSHR]

Yes. Flattened primers=high pressure. Remember the loads suggested in the manuals are not Gospel Truth, but merely what they have found to be safe in their test guns.

[zxcvbob]

Why would I be seeing flattened primers in a 357 with 8.0 grains of Power Pistol with a 158 grain JHP / JSP ?

Because the primer is hitting the frame of the gun ("recoil shield", I think it's called)

[snuffy]

Yes. Flattened primers=high pressure. Remember the loads suggested in the manuals are not Gospel Truth, but merely what they have found to be safe in their test guns.

Hogwash! Reading primers for pressure signs is like reading palms or tea leaves. Hokey science.

Especially unreliable for revolvers. Were the shells sticky during extraction? If no, then your loads are fine. No, I didn't look up his load! That's his job, if it's under max it should be alright.

[PowerPistol]

No sticky extraction

[Sevens]

Here's an experiment-- designed to make my point.

Make up f-i-v-e different handloads. Use the same brass, same primer (same lot!), same powder (same lot!), same bullet and loaded to same COAL with the same type/amount of crimp.

The only variance in these five loads should be the powder charge.
Make 6rds of them just over max
make 6rds of them 8% lighter
make 6rds of them 8% lighter still
make 6rds of them 8% even lighter
make 6rds of them even 8% lighter

Now, shoot all of these, same gun, same range session.
NOW, "read the primers." Now is a great time for you to make judgements, to attempt to gain insight and to build theories & conclusions based upon the appearance of fired primers.

The point? Trying to read in to the appearance of fired primers is futile unless:
1) you are seeing obvious signs of serious pressure issues... such as pierced, flowing, ruptured or in some cases, primer swipe

2) you are comparing exactly like items when trying to gain insight from fired primers

[mehavey]

Your elastic brass limit is your failure mode (357Mag frames.)
"No Sticky Extraction" = (most probable) No excess pressure for 357Mag frames.

Velocity sounds a bit high for that load (if you believe the manuals), but QL says it's about right for a 6" barrel and only mid-20s ksi.

What actual barrel length?

[jim8115]

6" GP 100

[yardbird]

Alliant says 8.0gr is max load with a 158JSP. Your velocity is low though. Federal primers?

[PowerPistol]

Winchester mag primers, though it seems to do it with any of them.

[Unclenick]

8 grains is already at Lee's maximum/never exceed limit for your combination. It's only 4% below Alliant's listed load for the Gold Dot HP using CCI 500 primer (not a magnum primer), and changing bullet make for one with a thicker jacket or changing primer type could easily reduce that number.

Western Powder's rule of thumb is to start rifle loads 10% and pistol loads 15% below maximum to allow for gun and component and load equipment variables, as well as for manual information artifacts. Some pressure measuring equipment (copper crushers) can err by as much as 25% or so, which is why you need to start low and not assume the maximum listed by the data author is your maximum. You should, by Western's approach, be starting at no more than 7.2 grains and working up.

As to primer flattening, it's an iffy thing to judge, as mentioned. For one thing, if you are using Federal standard pistol primers, their cups seem to be softer than most and flatten at lower pressures. If you are getting flattening alone, it's usually not serious. What happens is the primer raises pressure in the primer pocket faster than its gas can get out of the flash hole. This causes the primer to back out of the case and against the breech (recoil shield in your revolver) before the powder really gets burning. When the powder pressure builds high enough to force the case head back against the recoil shield, this reseats the primer. If the pressure is high enough, it's like trying to seat an inflated balloon, and the resistance causes seating force to push the rounded, inflated end of the primer flat.

When pressure gets still higher, the cup can be inflated to the point that the portion backed out of the primer pocket spreads out wider than the primer pocket. This is called mushrooming, and you can see it most clearly when you decap the fired case and inspect the spent primer for being wider at the flattened bottom of the cup. Another thing that can happen is cratering. This is when that inflating pressure on the primer is so high that it flows the primer cup around the firing pin and starts flowing it into the firing pin tunnel, making a small crater wall, like you'd see on the moon.

Mushrooming and cratering are clear signs you've exceeded the pressure the primer is comfortable with. Whether or not that has any relationship to pressure limits for your gun itself is another matter, but you don't want to run it that high with that particular primer, or you'll eventually get some primer piercing or leaking that gas cuts the breechface.

[buck460XVR]

Originally posted by snuffy:


Hogwash! Reading primers for pressure signs is like reading palms or tea leaves. Hokey science.

Especially unreliable for revolvers. Were the shells sticky during extraction? If no, then your loads are fine. No, I didn't look up his load! That's his job, if it's under max it should be alright.

I gotta agree. Except I looked up the load. According to Speer, 8gr of PP is dead center between min and max with a 158 jacketed projectile.

[mmb713]

Slightly loose primer pockets and hitting the recoil shield is the most likely explanation. Primers in rifles won't flatten until you're above 60 - 70,000 PSI. I highly doubt you're even above the SAAMI max of 35,000 PSI for the 357 Magnum. If cases are easily ejecting I wouldn't stress too much.

[jersurf101]

The one caliber I see flat primers in the most my .357 Magnum. Alliant 2400 flattens Federal and Winchester primers at mid power loads. CCI 500 and 550's seem harder. Just my experience.

[Unclenick]

mmb713,

Rifle primers typically have heavier cups than pistol primers, changing the pressure threshold for flattening.


Buck460XVR,

Yes, in the Speer manual, with Speer bullets, Speer brass, and a CCI500 standard pistol primer, but that's not what the OP is using. He listed Hornady, Nosler, and Zero bullets, and a Winchester small pistol magnum primer instead. I don't know what brass he has.

A recent Handloader article showed that switching components around, even when the bullets are the same weight, affects pressure more than most people suppose. Different primer start pressure, different bullet hardness, different lot of powder, different brass volume; after awhile that stuff all adds up.

On top of that, I've twice run into situations with a particular gun where the starting load listed in a manual was already at maximum for that gun. One was a .44 Special starting load in the old Hornady 2nd Ed loading manual fired in a light Charter Bulldog revolver. Stinging palm shooting from the bottom load followed by sticky extraction at the next higher load increment.

The other time was on this board a couple of years ago, and is apropos because this load came from the Speer manual. The poster had a Handi-Rifle in .243 Win that was still a full grain of powder below the maximum load, but that was popping the action open and giving him either 200 or 250 fps more velocity than the manual listed. I estimated he was at about 77,000 psi, which is just barely below the proof load range for that cartridge.

Only God is perfect: human beings make mistakes, and that includes load manual authors and pressure testers. There is no guarantee that a middle load in any manual will be healthy in your particular gun. That's why the starting loads are as low as they are, and it is why the bottom loads are called "starting" loads. You are supposed to start there. You work up while watching for pressure signs that could appear anywhere on your way up toward the listed top load, if they appear at all. You have to do the work up for yourself in your gun without assuming your gun will respond the way the load developer's gun did until you've proved it. It doesn't happen often that the bottom load in a manual will be near a gun's maximum, but it happens. You never want to start in the middle. Most especially not when you aren't matching the published load component list exactly.

Below is maybe the best reason for starting loads. This is from SAAMI's own documentation. It is a list of copper crusher pressure measurements done by nine different test facilities of the same lot of .30 Carbine reference ammo. Reference ammo is specially controlled ammo loaded to produce SAAMI MAP pressure. Note that the velocity measurements made only vary about 3½%, but that the pressure measurement results vary over 23%. Both can't be true at once. The reason we know it's the pressure measurements and not the velocity measurements that are lacking absolute accuracy is that the highest load MAP is 8 standard deviations above the bottom load MAP, something that could occur for ten rounds in a row (the ten tested for MAP) only once in many times the number of seconds in the age of the universe. So it's not normal randomness. Copper crushers are just a poor system of measurement. And yet manual data depending on copper crusher measurements is published all the time.

23% is in the ballpark of the pressure difference you get from a 10% reduced charge. That's why the 10% reduced starting load rule of thumb exists. The special exception of not downloading H110/296 still applies, but that powder produces low peak pressures relative to velocity anyway, so a different sort of safety margin is built into its formulation.

[Dave T]

The one caliber I see flat primers in the most my .357 Magnum. Alliant 2400 flattens Federal and Winchester primers at mid power loads. CCI 500 and 550's seem harder. Just my experience.

The above is my experience too. I shoot a 38/44 load of 2400 and a 158g bullet. It is sort of a +P+ for the 38 Sepcial case but only a mid-range for the 357 Magnum. Primers are always flat but the cases mostly drop out of the chambers or only take a little nudge from ejector rod.

Dave

[buck460XVR]

Originally posted by Unclenick:

8 grains is already at Lee's maximum/never exceed limit for your combination. It's only 4% below Alliant's listed load for the Gold Dot HP using CCI 500 primer

Buck460XVR,

Yes, in the Speer manual, with Speer bullets, Speer brass, and a CCI500 standard pistol primer, but that's not what the OP is using. He listed Hornady, Nosler, and Zero bullets, and a Winchester small pistol magnum primer instead. I don't know what brass he has.

There is no guarantee that a middle load in any manual will be healthy in your particular gun. That's why the starting loads are as low as they are, and it is why the bottom loads are called "starting" loads. You are supposed to start there. You work up while watching for pressure signs that could appear anywhere on your way up toward the listed top load, if they appear at all. You have to do the work up for yourself in your gun without assuming your gun will respond the way the load developer's gun did until you've proved it. It doesn't happen often that the bottom load in a manual will be near a gun's maximum, but it happens. You never want to start in the middle. Most especially not when you aren't matching the published load component list exactly.

Thanks for the intro to handloading Unclenick, but like you, I went thru that many years ago. No disrespect meant, but no where in my brief previous post did I claim the the OPs load was safe in his gun. I only agreed with snuffy that reading primers for pressure signs in revolvers was iffy at best. I then stated that the OPs load was in the mid-range according to Speer. No different than you stating he was at the upper end in the Lee. I didn't assume so, but were YOU saying his load was safe?

BTW....the OPs load of 8 gr is almost 6% less than max according to Alliant current info(8.5gr of PP)using 158gr Deep Curls(they are no longer GDs) and a CCI 500 primer. Since he did not state where he got his info, who knows......8 gr may be the starting load according to his source. Funny how starting loads in one book may be max in another. I've seen it more than once over the years. Been a topic on this forum several times. Good reason to always use more than one source when developing a new load with new components. PP would not be my first choice for true magnum velocities in .357 since it's burn rate is so close to Unique. It's more suited for medium velocity ammo in .357 and lower pressure calibers such as .38 special and .45ACP with smaller case volume. My experience in .357 is anytime you get 1200 fps or so from a 158 projectile, you'll have flattened primers......regardless of powder used and even with factory ammo.

[GP100man]

I also pitch my tent in the iffy camp.

Even after changing different lots of primers of the same make they can change thier primer pocket flow characteristics!

A much more reliable method is measuring the base of new unfired brass ,before & after & even then there are variables beyond our control.

[MSD Mike]

At one time I was using Unique at the upper end of its loading data for 158 gr JHP in .357 and I experienced flat and every once and awhile pierced primers. I switched to 2400 and got more velocity and better looking primers. Still flat but not real bad and no pierced primers. In both loadings cases dropped right out but with the slower powder my primers looked much better. This was in several revolvers so I rule out the gun as a variable.

Mike

[Unclenick]

MSD MIke,

About 20 years ago I was testing some 1964 M72 National Match ammo in several M1 Garands belonging to the club I was in at the time for use as loaners for beginners. That load had about 15% empty space in the case. If I tipped the muzzles down before firing, so the powder was away from the primer, the primer was nice and round edged. If I tipped the muzzle up before firing, so powder was back over the flash hole, I got flatten primers and about 80 fps more velocity.


buck460XVR,

Where I got the idea you were touting the safety of the load was your statement that you agreed with Snuffy, whom you quoted saying, in part:

…if it's under max it should be alright.

That, as you observe, begs the question, whose maximum?

I don't try to keep track of which board members know how much about what. Even the most experienced ones make the odd mistake here and there, myself included. Handloading in any form is an ongoing learning process, so all I can do is try to keep factual information straight, TBOMK. No disrespect is intended. If you look at the number of views on threads, you realize more people read them than participate in them, including non-member guests. You never know who will read what and believe it, so trying to keep facts sorted is important.

You said:

…Alliant current info(8.5gr of PP)using 158gr Deep Curls(they are no longer GDs)…

I'm curious to know where are you seeing that? Alliant's on-line data lists only "158 gr. GDHP" (Gold Dot Hollow Point) as the jacketed 158 grain bullet that I can find. Their print manual, page 68, includes one load using a Speer 158 grain UCHP (Uni-Core Hollow Point) bullet for the relatively new 300MP powder, but for all other listed powders still show 158 grain GDHP as their jacketed 158 grain bullet. Speer does have a note in their manual update data (free on line), stating that, unlike their rifle loads, the same load data applies to handgun Deep Curls as to Speer's other handgun jacketed bullets, so it may be a moot point as to which they use.

[madmo44mag]

I'm with many here.
Easy extraction = good to go.
One thing to consider is - is the brass old and the primer pockets worn enough to allow the primer to push back when fired?
I shoot straight wall pistol brass till it splits or the primer start to blow back and flatten.

[Tom Matiska]

My first guess is a burn rate issue. More a case of how quick your pressure is peaking and not how high it peaks. Straight wall pistol cases in a wheel gun(more liberal on head space) can be an education in burn rates.

With faster powder the case may expand and grab the chamber walls before it sets back. You may notice primers get pushed out and more case stretch with warm loads. A max load of h110 may generate higher pressures, but no primer flattening and require less trimming because the slower peak allows the case to set back before the case grabs the walls.

[Sevens]

It seems like many believe that the primer's flattened appearance is because of the whole cartridge case being push back against the recoil shield/breech face of the revolver.

I (obviously!) do not know for sure, but it's my opinion that what is happening is a bit different -- it's much more about the internal propellent gas that is going EVERYWHERE it can possibly go, and it's filling out the primer cup from the inside, up until the point where the bullet starts to move, and the pressure finds an escape route. That pressure is like water trying to find an escape route and it fills that primer cup from the inside, flattening it around the firing pin.

Different powders, or anything "different" in that incredible chemical reaction happening inside the cartridge case will make a primer "look" different.

[buck460XVR]

Originally posted by unclenick:

I'm curious to know where are you seeing that? Alliant's on-line data lists only "158 gr. GDHP" (Gold Dot Hollow Point) as the jacketed 158 grain bullet that I can find. Their print manual, page 68, includes one load using a Speer 158 grain UCHP (Uni-Core Hollow Point) bullet for the relatively new 300MP powder, but for all other listed powders still show 158 grain GDHP as their jacketed 158 grain bullet. Speer does have a note in their manual update data (free on line), stating that, unlike their rifle loads, the same load data applies to handgun Deep Curls as to Speer's other handgun jacketed bullets, so it may be a moot point as to which they use.

If you go to the Speer website you'll see they no longer have a 158gr "Gold Dot" in 38 caliber anymore, but they have a bonded 158 gr HP in the "new" line of Deep Curls. If you look close you'll see their product number is the same for the "new" Deep Curl" as it was for the "old" Gold Dot. When I e-mailed Speer about it, they told me the bullet is exactly the same, but the name was changed to differentiate between Gold Dots intended for SD and those intended for hunting. Same goes for their 240 and 270 grainers in .44 caliber and their .45 caliber 300 grainer I use in my .460. This name changed occurred just a coupla years ago so older data will not reflect it.

[Unclenick]

OK. So I'm not imagining things. The Deep Curl is not in Alliant .357 Mag nor in Speer .357 Mag published load data. It's just in Speer's bullet catalog that the 158 grain GDHP has disappeared. Very odd, since I have no trouble finding 158 grain GDHP loaded ammunition currently cataloged by Speer, here. I'd say Speer has succeeded in creating some needless confusion. Anyway, the OP isn't using any Speer bullets that I can see, so he's neatly sidestepped the issue.