Pressure signs.
- Thread starter Shadow9mm
- Start date
kilotanker22
New member
The bottom ten almost appear to have some gas leakage past the primer. I can't be sure of that from a photo though. It is evidenced by the dark ring around the primers and the increased amount of soot on the case head.
I could be way off base though. That is just my observation.
I could be way off base though. That is just my observation.
kilotanker22
New member
At the same time, the top row of primers look flatter than the bottom. I wouldn't have any idea which were hotter.
Here's a 22-250 that just came into my shop a few weeks ago. What do the experts think the pressure was on this one?
Sure. How many proof loads can your rifle survive? When you proof test a rifle, you shoot one or two proof loads. Some reloaders are shooting proof loads continusouly.
That there is a pressure sign!! Sure thing!! I'd put the pressure at "Too Much!"
And that primer pocket looks loose. I would not shoot any more of those. Back off at least a grain! Maybe two!
I'm curious,did that case crushing come after the fact,or in the chamber? The reason I ask is a co-worker showed me a crushed case and asked me what caused it. I thought maybe a very short bullet,maybe a 40 or 50 gr boat tail allowed pressure to bypass the bullet back into the chamber. outside the case..my guess.
And that primer pocket looks loose. I would not shoot any more of those. Back off at least a grain! Maybe two!
I'm curious,did that case crushing come after the fact,or in the chamber? The reason I ask is a co-worker showed me a crushed case and asked me what caused it. I thought maybe a very short bullet,maybe a 40 or 50 gr boat tail allowed pressure to bypass the bullet back into the chamber. outside the case..my guess.
I've been loading for around 50 years and had only one ka-boom which fortunately did not destroy my rifle. How it happened may be of some education to our newer reloaders who sometimes want to start in the middle or upper third of the recommended powder charges.
I was working up loads with a new powder and as usual started at the bottom of the powder charge range and increased by 0.5 grains up to the top of the range. Gun was a .30-06 so I felt the half grain increase was reasonable given the case capacity.
Had a 50 round loading tray with five across and ten down. Top row with the lowest charge was row A, shot 1 through 5; second row B, 1 through 5, etc.
Somehow due to lack of attention on my part I set the loading tray upside down so that now the hottest loads were in the first row. These loads were only the max ones in the load book; I never exceed the max.
Well, that first round which should have been the start powder amount in the load book but was in fact the highest amount went ka-boom! Shooting glasses immediately fogged from powder blow back cheek stinging and scared sh----les. Had to hammer the bolt open and out falls the primer. Upon extraction, the case primer pocket was huge.
The point of the above is that the ka-boom happened without exceeding the maximum charge listed in the book. So those who start in the middle or upper third of a charge range are walking on very thin ice.
As has been said countless times: START AT THE BOTTOM AND WORK UP!
Do not assume the upper range of the loads in the book are still safe in YOUR gun.
I was working up loads with a new powder and as usual started at the bottom of the powder charge range and increased by 0.5 grains up to the top of the range. Gun was a .30-06 so I felt the half grain increase was reasonable given the case capacity.
Had a 50 round loading tray with five across and ten down. Top row with the lowest charge was row A, shot 1 through 5; second row B, 1 through 5, etc.
Somehow due to lack of attention on my part I set the loading tray upside down so that now the hottest loads were in the first row. These loads were only the max ones in the load book; I never exceed the max.
Well, that first round which should have been the start powder amount in the load book but was in fact the highest amount went ka-boom! Shooting glasses immediately fogged from powder blow back cheek stinging and scared sh----les. Had to hammer the bolt open and out falls the primer. Upon extraction, the case primer pocket was huge.
The point of the above is that the ka-boom happened without exceeding the maximum charge listed in the book. So those who start in the middle or upper third of a charge range are walking on very thin ice.
As has been said countless times: START AT THE BOTTOM AND WORK UP!
Do not assume the upper range of the loads in the book are still safe in YOUR gun.
No, I crushed the case taking it out of the bolt face. The extractor recess lip in the bolt was peeled out and the extractor was stuck in the case (that's the extractor on the bench behind the case).
The blowout filled the firing pin hole and pushed the firing pin backwards about 1/8". I was wondering why it looked like the rifle was cocked.
The case protruded into the ejector plunger hole about 1/16", bolt head swelled outwards to fill the barrel bolt head recess, had to press the bolt out of the receiver because the bolt head was swelled larger than the bolt way.
That piece of slver colored metal next to the case is the primer. I think that is what they mean when they talk about flattened primers.
I could lie and tell you this was just a hot load, but the customer came clean and told me he had been loading HS6 before he started loading 22-250. He just forgot to empty out the powder measure. That is what 40 gr of HS6 behind a 55 gr bullet does to a Rem 700.
Jim Watson
New member
A guy here neglected to take the Varget out of his powder measure before adding BR50 powder for his AR50 rifle. Recoil was reported stout, even when he got down to the interface and was loading some of both. Rifle was not damaged.
How much pressure on that case??? My guess would be probably between 90-110K psi, certainly above 90K psi. Possibly a lot above....
I base this guess on a similar accident I had when I was 15. Rifle was a Rem 600 in .308 Win. I had been working on a cast bullet "plinking load", using Unique. My mistakes were multiple, and I was lucky, in the long run...
First mistake, I did not have a powder trickler.
I used a fired case, to dribble powder into the scale pan.
Next mistake: mistakenly using a sized primed case as the trickler, instead of the fired case I thought it was.
Third mistake: Putting that primed case (about half full of pistol powder) into the loading block with the cases I was going to load.
4th mistake, seating a bullet in that case and later firing it.
Got hit on the face with gas. Bolt was frozen shut. Gunsmith did manage to get it open and "chisel" the case out (a couple wacks on the rim did it)
Case head had expanded to the point where the primer fell out. There were 3 different cracks in the case web. There was a "belt" of brass swaged on the case body just ahead of the extractor groove. research I did at the time said those signs were the result of between 90-110k psi.
The rifle suffered a broken extractor, and pin, and a broken safety pin. Otherwise unharmed. No cracks were found, and the repaired rifle is still in my possession today and seems none the worse now, some 50+ years later.
Gunsmith said (at the time) that Remington proofed their rifles to 90Kpsi, and I was "lucky".
Still have the case, in a baggie, hanging over the bench, as a reminder....
I base this guess on a similar accident I had when I was 15. Rifle was a Rem 600 in .308 Win. I had been working on a cast bullet "plinking load", using Unique. My mistakes were multiple, and I was lucky, in the long run...
First mistake, I did not have a powder trickler.
I used a fired case, to dribble powder into the scale pan.
Next mistake: mistakenly using a sized primed case as the trickler, instead of the fired case I thought it was.
Third mistake: Putting that primed case (about half full of pistol powder) into the loading block with the cases I was going to load.
4th mistake, seating a bullet in that case and later firing it.
Got hit on the face with gas. Bolt was frozen shut. Gunsmith did manage to get it open and "chisel" the case out (a couple wacks on the rim did it)
Case head had expanded to the point where the primer fell out. There were 3 different cracks in the case web. There was a "belt" of brass swaged on the case body just ahead of the extractor groove. research I did at the time said those signs were the result of between 90-110k psi.
The rifle suffered a broken extractor, and pin, and a broken safety pin. Otherwise unharmed. No cracks were found, and the repaired rifle is still in my possession today and seems none the worse now, some 50+ years later.
Gunsmith said (at the time) that Remington proofed their rifles to 90Kpsi, and I was "lucky".
Still have the case, in a baggie, hanging over the bench, as a reminder....
reynolds357
New member
I remember reading about Ackley becoming quite annoyed that he could not blow up a Mauser 98 using Rifle powder. I remember reading about Roy Weatherby pushing a Mark V over 125000PSI (trying to get 5000 FPS) and not damaging it.
Pressure signs, ball powder No. 9 Hodgdon data, 357 magnum
Reading Primers...........
Following Hodgdon data, No. 9 powder locked up my S&W M28-2 357 mag. See the whole story here- https://www.thehighroad.org/index.php?threads/s-w-m28-2-357-magnum-high-pressure-locked-action.905609/
More photos at link.
Ok, so my bullet was 164.5 grs lubed. A little heavier then 158gr in the data. But is that enough difference to blank a primer that extruded a pin type projectile , locking the cylinder? 1 shell loaded at maximum of 12.4 grs?
Reading Primers...........
Following Hodgdon data, No. 9 powder locked up my S&W M28-2 357 mag. See the whole story here- https://www.thehighroad.org/index.php?threads/s-w-m28-2-357-magnum-high-pressure-locked-action.905609/
More photos at link.
Ok, so my bullet was 164.5 grs lubed. A little heavier then 158gr in the data. But is that enough difference to blank a primer that extruded a pin type projectile , locking the cylinder? 1 shell loaded at maximum of 12.4 grs?
"My friend fired his M19 first, firing over the Chrony and he doubled the gun (fired two shots instead of one). To this day, I don't know how he did it, and neither did he (he said...)"
I think I know what happened.
I saw a similar incident a few years back. I was at the range with my son in law and two grandsons and one of the guns we used was my S&W 629 .44 magnum. I'd just finished shooting the first set and the son in law who'd never shot anything heavier than a .38 Spl. wanted to try the gun. I king of told him to hang and when he touched off the first round several things happened. He didn't double, he tripled. What I think happens is he felt the recoil, relaxed his trigger finger. then, literally clenched the gun tryinh yo hold it down pulling the trigger again in the process, twice after the first pull which was done in single action mode. First shot level, second shot about a 45 degree angle and the third shot about a 75 degree angle. First time I've ever seen a revolver go full auto. 
To this day if I ask if he wants to go shooting he'll say OK, but leave that damn .44 at home.
Paul B.
I think I know what happened.
I saw a similar incident a few years back. I was at the range with my son in law and two grandsons and one of the guns we used was my S&W 629 .44 magnum. I'd just finished shooting the first set and the son in law who'd never shot anything heavier than a .38 Spl. wanted to try the gun. I king of told him to hang and when he touched off the first round several things happened. He didn't double, he tripled. What I think happens is he felt the recoil, relaxed his trigger finger. then, literally clenched the gun tryinh yo hold it down pulling the trigger again in the process, twice after the first pull which was done in single action mode. First shot level, second shot about a 45 degree angle and the third shot about a 75 degree angle. First time I've ever seen a revolver go full auto. To this day if I ask if he wants to go shooting he'll say OK, but leave that damn .44 at home.Paul B.
The pressure sign topic comes up periodically. Denton Bramwell's data in this article, in which he used a Pressure Trace to get actual reading to correlate to case head expansion and pressure ring expansion, shows the same lot of cases with the same load history have about a 2:1 range of pressures over which one case or another will show the same amount of expansion. We've all seen primers do this at one time or another, where most look fine and then one pierces.
Below is a table of data from SAAMI that shows the same reference load measured by different copper crushers. Note that the readings vary by 23% from one facility to the next, and this is using extremely uniform calibrated copper slugs and tight tolerance SAAMI pressure and velocity barrels. Now consider that primers and cases are also copper alloys and that by looking for pressure signs in them, you are looking at how they deform. They are not calibrated, nor are they as precisely uniform as the slugs, so how accurate can pressure readings based on their degree of deformation be? This explains how a 2:1 difference in pressure indication of can occur with them.
Basically, a pressure sign tells you what the component or gun being used can tolerate in combination with one another. It is pretty common for a case wall to be a couple of thousandths thinner on one side near the web than on the other, not to mention weight differences from coming off different tooling. So it's not really hard to understand why pressure signs that occur every now and then may not be present at all with other cartridges made the same way.
So, why do you care what the pressure is, short of blowing up the gun? There are two areas of concern:
1.) Will the ammo be used in more than one gun, either intentionally or unintentionally (e.g., a not too brilliant nephew (didn't you warn your sister not to marry his father?) gets their hands on your reloads and tries them in his gun)?
2.) Wear and tear. (How many rounds before the throat is shot out? How soon will lug setback become apparent? Will you have enough additional primer leaks over time to scar your bolt face significantly? (Do you ever expect to be able to sell this gun to anybody else?) Guns designed for a particular cartridge have lifetime considerations for which the designer assumed the normal pressure limit for the cartridge would be observed. There is no simple way to guess how much difference to durability will be made by shooting at pressures over that number.
The bottom line is the one you've seen echoed repeatedly in many places. Find a reasonable load that maximizes accuracy in your gun, as shot placement is more important than power the vast majority of the time. If you need more power, get a gun chambered for a cartridge that delivers it rather than shorten your gun's life in an unpredictable fashion.
Below is a table of data from SAAMI that shows the same reference load measured by different copper crushers. Note that the readings vary by 23% from one facility to the next, and this is using extremely uniform calibrated copper slugs and tight tolerance SAAMI pressure and velocity barrels. Now consider that primers and cases are also copper alloys and that by looking for pressure signs in them, you are looking at how they deform. They are not calibrated, nor are they as precisely uniform as the slugs, so how accurate can pressure readings based on their degree of deformation be? This explains how a 2:1 difference in pressure indication of can occur with them.
Basically, a pressure sign tells you what the component or gun being used can tolerate in combination with one another. It is pretty common for a case wall to be a couple of thousandths thinner on one side near the web than on the other, not to mention weight differences from coming off different tooling. So it's not really hard to understand why pressure signs that occur every now and then may not be present at all with other cartridges made the same way.
So, why do you care what the pressure is, short of blowing up the gun? There are two areas of concern:
1.) Will the ammo be used in more than one gun, either intentionally or unintentionally (e.g., a not too brilliant nephew (didn't you warn your sister not to marry his father?) gets their hands on your reloads and tries them in his gun)?
2.) Wear and tear. (How many rounds before the throat is shot out? How soon will lug setback become apparent? Will you have enough additional primer leaks over time to scar your bolt face significantly? (Do you ever expect to be able to sell this gun to anybody else?) Guns designed for a particular cartridge have lifetime considerations for which the designer assumed the normal pressure limit for the cartridge would be observed. There is no simple way to guess how much difference to durability will be made by shooting at pressures over that number.
The bottom line is the one you've seen echoed repeatedly in many places. Find a reasonable load that maximizes accuracy in your gun, as shot placement is more important than power the vast majority of the time. If you need more power, get a gun chambered for a cartridge that delivers it rather than shorten your gun's life in an unpredictable fashion.
Attachments
Well, I can deduce that is was at least 80,000 psi by the way the brass flowed to fill all of the empty spaces around. The case head had swelled and brass had flowed out between the bold and the barrel, into the ejector hole, literally everywhere it could go. I have read that brass flows like that above 80,000 psi, so that is as far as I am willing to guess.
The bolt head swelled to fill the barrel recess, and the barrel threads were really tight coming out of the receiver, so I'm going to guess the barrel shank swelled a few thousandths as well. I'm sure some bright engineer could calculate it all out since we know the rifle is made of 4140 or equivalent steel.
My reason for posting this was to emphasize what I posted earlier in the thread. If you have pressure signs, it's already over pressure standards, you're just trying to guess how far you can skate on thin ice.
44amp,
I only got one case stuck in my entire life and the powder was AA7 and the cartridge was in 9mm largo. This was years ago and I really couldnt find much load data, so being an idiot, I loaded to MAX well apparently If I recall there was some issues years ago with AA7 and its burn rate, and it was way to hot for the charge I used, those largo cases are long and you can really fill them up not in a good way I might add
Luckily the star super b I had was fantastically made and saved my hands. (Maybe There is Something to Spanish Steel) I learned a valuable lesson that day. Never ever start at MAX
Case was Starline… and it literally flattened the primer so bad you barely tell where the firing pin struck the primer. I have it saved somewhere
I only got one case stuck in my entire life and the powder was AA7 and the cartridge was in 9mm largo. This was years ago and I really couldnt find much load data, so being an idiot, I loaded to MAX well apparently If I recall there was some issues years ago with AA7 and its burn rate, and it was way to hot for the charge I used, those largo cases are long and you can really fill them up not in a good way I might add
Luckily the star super b I had was fantastically made and saved my hands. (Maybe There is Something to Spanish Steel) I learned a valuable lesson that day. Never ever start at MAX
Case was Starline… and it literally flattened the primer so bad you barely tell where the firing pin struck the primer. I have it saved somewhere
Last edited:
One of the most reliable pressure indicators I have found is my Chrono. Even with a shorter/longer barrel if your FPS is way over what is predicted you are most likely overpressure. My best remembered experience was with 142's and H4350. Using Hogdons starting load I had 2950 FPS. I didn't need a pressure trace or anything else to know that I was overpressure
of you are referring to my post I suggest you reread it. I fired one round at the books lowest suggested charge, looked at my chrono reading packed up my gear went straight home and pulled all those bullets to check that I had not overcharged. I had not.
Then I checked the load table for 6.5 CM which is essentially the same cartridge and reloaded using that starting data and all was well. To this day Hodgon's starting load for the .260 Rem using 142's and H4350 is the maximum load for the 6.5 CM. Put that in a 30 inch barrel and you have a major problem ready to happen. To put it in perspective the .260's case capacity is 1 grain of water more than the 6.5 CM
To this day I always check any new .260 Rem load data against the CM data to make sure they are close