Pressure Signs from Your Gun

[justindad]

When working up a load, the manuals tel you to look at primers. For low to medium pressure rounds, flattened or punctured primers is way too high. My Uberti SAA will have its screws loosen when I’m at about 75% of max pressure. My Sig P320 will fail to extract a .357Sig case when the pressure is ~10% above max. When I stick my .40 barrel in the P320 and shoot max book loads, the brass will bulge to the point where it pushing it through the bulge buster die requires significantly more force than usual.
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What do your guns do when pressures are near max?

[charlie b]

Sometimes the cases simply stick a bit. Hard to tell in some semi-autos unless they fail to extract. I've had a few guns that showed no signs of overpressure when above book loads. Depends on the gun and cartridge.

Primers for me have not ever been good at showing over pressure. I've had several guns that flattened primers with factory loads or at loads near book starting levels. OTOH, I've had cartridges loaded beyond max and the primers looked same as when they were loaded.

Basically, I rely on book loads to tell me where max is. If I run into issues before that (extraction, ejection) then I stop and mark that as my max.

Or....find someone with the right equipment to measure load pressures :)

[Hannibal]

When working up a load, the manuals tel you to look at primers. For low to medium pressure rounds, flattened or punctured primers is way too high. My Uberti SAA will have its screws loosen when I’m at about 75% of max pressure. My Sig P320 will fail to extract a .357Sig case when the pressure is ~10% above max. When I stick my .40 barrel in the P320 and shoot max book loads, the brass will bulge to the point where it pushing it through the bulge buster die requires significantly more force than usual.
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What do your guns do when pressures are near max?

I don't understand why people want to push max loads. I stick with 10% below max or more. If you need more energy choose a different caliber. You're just asking for trouble in my experience by doing otherwise.

[Dusty Bannister]

It appears that you are speaking about primer appearance on handguns. The way I understand the comments in the manuals is that primer appearance will tell you when you have exceeded safe pressures, ie flat or cratered/punctured primers.

[Winger Ed.]

I wouldn't trust primers of different brands to 'record' the same pressure level signs for the same load.

A firearm is basically a machine. They break. They wear out. The harder you push it, the sooner one or the other will happen.
Just like your car- it might be able to do 125 mph, but it'll last a lot longer if you keep it under about 80.

I tell folks, what was told to me many years ago about getting up to and over max. pressures:
"If you want the performance of a .300WinMag---- buy one. Don't try to make one yourself out of a .308."

[justindad]

I don't understand why people want to push max loads. I stick with 10% below max or more. If you need more energy choose a different caliber. You're just asking for trouble in my experience by doing otherwise.

I have NOE & MP molds for which there is no load data. One of mine will surely give over pressure when staying under book max charge for same bullet & case fill. I’m always looking for signs of over pressure.

[poppy42]

Couldn’t tell you because I don’t shoot my guns at max pressures or beyond

[stubshaft]

Couldn’t tell you because I don’t shoot my guns at max pressures or beyond

Me neither.

[Hick]

I not only don't trust primers as an indication of pressure-- I think anyone who relies on that is wrong. Consider this: The 416 Remington Magnum, for example, uses a large rifle primer and has typical pressures of 60,000 psi or more, while the 30-30 runs more like 40,000 psi and uses the same size primer. The Large rifle primer does not flatten when hit by that 60,000 psi pressure-- so it would seem we need to go over 60,000 psi in that 30-30 case before we see a flattened primer (The Rem Magnum, of course would use a magnum primer-- but all the info I can find indicates that the magnum primer does not have a thicker metal casing). The logic in looking at primers seems to be that when you go over rated pressure for your case primers will flatten. This overlooks the fact that the primers are built to withstand the pressures of the highest pressure cartridge that uses that type primer.

[kevin c]

One word: competition.

Many wanting to win will investigate whatever they think will give them an advantage. That means pushing beyond conventional or common sense boundaries.

In action pistol, there is a minimum bullet weight and momentum based “power factor” meant to prevent mouse fart loads. The desire to minimize felt recoil (allowing fast follow up shots) has had folks experimenting with heavy bullets and very fast powders to the point that, in the early years of the sport, damaged guns from hot load case blowouts were not rare. A later drop in the PF reduced that, but there are still folks who push it.

[243winxb]

Not I. Others https://www.thehighroad.org/index.php?media/albums/high-pressure-signs.148/

Then there is KABOOM https://www.thehighroad.org/index.php?media/albums/kaboom.24/

[pworley1]

I don't even run my jacketed loads at max pressure. I keep things mostly in the moderate load range. If I need more than that I use a bigger gun.

[atr]

...I don’t shoot my guns at max pressures or beyond

If I do approach maximum loads then I weight each load individually and carefully.
best
atr

[Larry Gibson]

"Basically, I rely on book loads to tell me where max is. If I run into issues before that (extraction, ejection) then I stop and mark that as my max."

"The way I understand the comments in the manuals is that primer appearance will tell you when you have exceeded safe pressures, ie flat or cratered/punctured primers."

"If you want the performance of a .300WinMag---- buy one. Don't try to make one yourself out of a .308."

All the above are excellent comments and advise. As one who has actually measured the pressure of thousands of cartridges, including those cartridges chambered in Uberti revolvers, by the time you reach any of the, so called, "pressure signs" with handgun cartridges [those with max loads from 14,000 up through 45,000 psi which excludes the specialty revolver and SS cartridges] such as flattened primers, sticking cases and bulging cases the pressure has exceeded the established maximum loads by a very great amount. Actually such loads may well be above even "proof" levels. Use of such is not to be recommended.

I do have to admit loading for an Uberti and using loosening screws ["Uberti SAA will have its screws loosen when I’m at about 75% of max pressure"] as a measurement or indication of pressure percentage is a new one on me:-?

[Daekar]

I only ever view max loads as a bit flexible when using firearms that I know are much stronger than the max pressure for the cartridge in question, and even then I go carefully. In general, if I see primer symptoms, that's too hot and I back it down. The only symptom of overpressure that I have ever seen, apart from primers, is increased effort required to open an action, and that's an immediate serious red flag indicating I started to rely on my guardian angels a bit too much.

I feel like primers should only be seen as a source of information if you're using a gun which is strong enough to fire the highest pressure cartridges which use that primer. If your gun is good for a cartridge rated at 60k PSI and you're working up loads for something with max pressures lower than that, like a 30-30, then technically you have a bit of safety margin. That being said, since pressures can spike VERY quickly when exploring the upper limits of charge weight, it's not nearly as much safety margin as you might think.

In pistols, I never go to max loads. It's not necessary and is harder on the gun.

[justindad]

I evaluate my rounds during firing and afterwards, even when I’m shooting 140 grain wadcutters at 900 fps from .357 Mag brass. Cleanliness of burn, carbon on the outside of the brass, shot-to-shot velocity variance. Looking for pressure signs need not be limited to fools soon to loose their fingers.

[uscra112]

In some instances a flattened primer is indicating a headspace issue, nothing to do with pressure.

[Rapier]

When testing loads, especially with cats, I pay attention to all the signs of OP not just primers, scrape marks, ejector marks, web expanding, etc. But once indicated OP occurs, I back off to the next load down in pressure with accuracy for hunting. It makes little sense to over rev an engine or intentionally OP any gun, especially for cast bullet shooting of paper targets.

[justindad]

I’m going to rephrase the question: “Have you ever experienced an overpressure condition while staying within book load limits? If so, how did you know? Additionally, what do you look for in your gun so that you are able to notice that you had an overpressure condition even when staying within book charge & seat depth limits?” I think answers to these questions are helpful to the general reader here. The point is not me trying to overload my cartridges.
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I was something like 0.4 grains under max charge (and my OACL was greater than book by about 0.02”) with Enforcer when my .357 Sig case failed to extract. If I wasn’t thinking critically and judging the book data, I would have figured the problem was my gun, then installed an aftermarket extractor claw (which is available), and proceeded to the max book charge while completely ignorant of the safety hazard.

[gwpercle]

Primers can be deceiving ... so don't go by primer condition alone .

My favorite indicator is "sticky" extraction .
If you have to pound them out ...those loads are too hot .

Another sure sign is primer pocket enlargement . If on the next reload the primers fall out the pockets ... go back and look at that load ...chances are it's too hot !

Gary

[mdi]

When I was pushing mu 44 Magnums, during a bad case of "Magnumitis",, I measures the case head before and after firing. If there was any expansion , beyond .001"-.002" I would double check my data and back off. I don't know how accurate this is and I just read it in a reloading text somewhere. As far as sticky extraction, I dunno. I had a definite over load of some 357 Magnum handloads (my fault, stupid mistake). I fired 5 shots, opened the cylinder and the fired cases, along with loose primers fell out of the cylinder...

[Dusty Bannister]

357 Sig? I would be looking at the chance of bullet movement when chambering. Maybe not so much if you did the "press against the bench" test. If a bullet is powder coated, your cartridge OAL might change as well.

[dverna]

Another "pansy" who uses the published loads to establish maximums. And I never go to maximum. I do not shoot large and/or dangerous animals. If I did, I would buy the appropriate caliber. In northern MI, with jacketed bullets, the .308 is enough gun even at starting loads.

[fredj338]

When working up a load, the manuals tel you to look at primers. For low to medium pressure rounds, flattened or punctured primers is way too high. My Uberti SAA will have its screws loosen when I’m at about 75% of max pressure. My Sig P320 will fail to extract a .357Sig case when the pressure is ~10% above max. When I stick my .40 barrel in the P320 and shoot max book loads, the brass will bulge to the point where it pushing it through the bulge buster die requires significantly more force than usual.
*
What do your guns do when pressures are near max?

First how do you know what the pressures are, 75% of, 10% over, how?
Every gun is diff, but some of the things you are describing are not pressure issues. Loose screws, recoil, not pressure. Failure to extract, most likely an extractor issue unless the case is stuck in the chamber & that is waaaay over 10%. Bulged cases with std pressure ammo, barrel issue.
I base line test with factory ammo if available.
With true flattened primers, you are generally way over for pressure for that gun, though some brands are just soft. Case head marks are a good indication of over pressure, its just tough to say how much over. Measuring case head expansion can also tell you a lot but you need a baseline with factory to set that. Every chamber is diff. Plus brass is diff, very diff in some instances. Federal rifle brass is very soft in my exp. I will get loose primer pockets with loads that are fine in say Norma or Lapua or Win brass. When running max loads, everything matters.

[fredj338]

In some instances a flattened primer is indicating a headspace issue, nothing to do with pressure.

Or just soft primer cups.

[Outpost75]

A sure indicator in rifles is loosening primer pockets starting with a new case and then reloading and firing it ten times. If primer seating is too easy before ten reloads pressure is over 55,000 psi.

In revolvers by the time you get hard extraction you are already at proof pressure.

Better indicator is to measure end shake, correct to zero, then fire 100 rounds. If end shake develops more than 0.002 you are already at proof pressure. If gun goes 500 rounds without loosening you are good to go.

[45_Colt]

Just a couple of ideas. A chronograph is helpful. If the velocities are on the high side, something isn't right. This is a good method.

Pierced primers don't mean a lot. Had a guy at the range shooting factory ammo in a factory handgun. Ended up with a pierced primer on every round. Changed the ammo, same thing. Ended up being a sharp protrusion on the firing pin.

OTOH (on the other hand), if a firearm hasn't shown pierced primers, but then suddenly does. Maybe look out. The issue here is that it could be over pressure, or a batch of soft primers. So still not sure.

Flattened primers are not a good way to judge over pressure. The 45 ACP is a low pressure round. Flatten primers in it and we are way, way, over pressure.

I have seen a lot written about mic'ing the case heads for expansion. May be legit, I don't know. But in the articles I've read, it appeared to be (OK).

In closing I will go back to a chrono. Excess velocity means something isn't right. Or, the velocity doesn't increase as much as the increase in powder charge should entail.

45_Colt

P.S. quick edit, as others have stated, I tend to not push the limits...

[fredj338]

Just a couple of ideas. A chronograph is helpful. If the velocities are on the high side, something isn't right. This is a good method.

Pierced primers don't mean a lot. Had a guy at the range shooting factory ammo in a factory handgun. Ended up with a pierced primer on every round. Changed the ammo, same thing. Ended up being a sharp protrusion on the firing pin.

OTOH (on the other hand), if a firearm hasn't shown pierced primers, but then suddenly does. Maybe look out. The issue here is that it could be over pressure, or a batch of soft primers. So still not sure.

Flattened primers are not a good way to judge over pressure. The 45 ACP is a low pressure round. Flatten primers in it and we are way, way, over pressure.

I have seen a lot written about mic'ing the case heads for expansion. May be legit, I don't know. But in the articles I've read, it appeared to be (OK).

In closing I will go back to a chrono. Excess velocity means something isn't right. Or, the velocity doesn't increase as much as the increase in powder charge should entail.

45_Colt

P.S. quick edit, as others have stated, I tend to not push the limits...

Yes & no. I had a Ruger SS 2 3/4" that was very fast, faster than my 4" guns. Unless you have something to compare to, the book data is a guide. It is certainly possible to get say 100fps more vel out of a book load in a given firearm. So it just depends. The flip side of that is understanding what the chrono is telling you. I had a friend call me & complain he couldnt get to the book vel in his 9mm Kahr before hitting pressures. Yeah the bbl length matters. So while I think a chrono is invaluable, especially working without book data, one needs to understand the variables & what the chorno is telling you. Reading pressure signs can be tricky. Even enlarged primer pockets isnt a given, depends on the brass.

[405grain]

I load for accuracy not velocity. Generally, if there's a published starting load and a maximum load, my loads will be about in the middle between them. I've always felt that by the time you start to see pressure signs you're already in too high. If I want more power for a hunting load I just choose a bigger, heavier bullet.

[charlie b]

Primer pockets. I never had a problem with them until I got a .223 bolt gun. Loaded a bit less than max and most brands of cases enlarged primer pockets at 4 or 5 reloads. Too high pressure? Maybe.

I then bought Lapua brass. Those now have over 20 reloads on them, with slightly hotter loads, and are still fine. No split necks either. Volume wise they are in the middle of all the brands I tried.

[justindad]

I do have to admit loading for an Uberti and using loosening screws ["Uberti SAA will have its screws loosen when I’m at about 75% of max pressure"] as a measurement or indication of pressure percentage is a new one on me:-?
It’s not super reliable, but starts at around 8.0 grains of Unique with a 255 grain bullet. Correlating clamp force to torque is surprisingly unreliable for those who have had to look closely at such in machine design. If I tighten the screws around the ejector rod and grips with my finger nail and they don’t move after 50 rounds, I’m in safe territory… definitely below those tier 2 or .45ACP+P loads some folks go after with a Uberti SAA.

[Outpost75]

Primer pockets. I never had a problem with them until I got a .223 bolt gun. Loaded a bit less than max and most brands of cases enlarged primer pockets at 4 or 5 reloads. Too high pressure? Maybe.

I then bought Lapua brass. Those now have over 20 reloads on them, with slightly hotter loads, and are still fine. No split necks either. Volume wise they are in the middle of all the brands I tried.

Military cases use a process called "pre-pocketing" which uses an additional work hardening step to produce a head hardness in the region of 180 Vickers Diamond Pyramid Hardness, abbreviated DPH.

Commercial brass which does not undergo this additional step seldom exceeds 170 DPH. Federal brass is well known for having softer heads in which the primer pockets loosen. In 5.56mm military cases using a primer pocket swage to remove the crimp is better with respect to maintaining size and also inducing a bit more work hardening of the primer pocket edges.

[billmc2]

I don't know how to read signs either, so I've read through this trying to learn. I'd like to ask a question, that is a little deviation, but not to far off.

A number of years back I was a member of a forum (which is off the air now) that was dominated by LEOs. They convinced me to by a case of Federal 9BPLE, which is a 115 gr +P+ load. From my research about it at the time, along with their comments and shooting a gun that Police issue, I felt I'd be safe. I shot quite a few rounds but still have some left. I've been collecting my brass long before I started to reload.

Last week I decapped about 1000 9mm cases. I noticed I was having trouble getting the cases from the 9BPLE into the shell holder. When I looked at the primers, to my untrained eye, they looked like they were cratered and the primer had raised enough around where the pin struck, causing the difficulty with the shell holder.

I am now questioning whether or not I should shoot what I have remaining. There was no problems with firing, just the observation I made knocking out the primers. Opinions would be welcomed.

[dtknowles]

Stay with book loads, check with chronograph, if you see high velocity or any pressure signs, back off. Primers, extraction, head expansion, short brass life, any negative sign, back off.

[charlie b]

Military cases use a process called "pre-pocketing" which uses an additional work hardening step to produce a head hardness in the region of 180 Vickers Diamond Pyramid Hardness, abbreviated DPH.

Commercial brass which does not undergo this additional step seldom exceeds 170 DPH. Federal brass is well known for having softer heads in which the primer pockets loosen. In 5.56mm military cases using a primer pocket swage to remove the crimp is better with respect to maintaining size and also inducing a bit more work hardening of the primer pocket edges.

Thanks for that info. Unfortunately some of the cases I had trouble with were Lake City surplus. Only 5 reloads before primers failed to stay seated. Just another reason why I don't rely on these kinds of things for signs of over pressure as they are not consistent.

I have been contemplating the purchase of the Pressure Trace system for a couple of years now. One of these days...... :)

[StrawHat]

I was taught that reading primers could work with rifles but not at all with handguns. Larry Gibson’s post seem to reiterate that.

Kevin

[Cane_man]

model the load in Quickload, it has always done me right (along with published loads) and steered me in the right direction

[gilgsn]

Hello. Here is my $0.02, how I proceed with load development.
First, a chronograph is a must. While not a direct measurement of pressure, it is a good indication.
You can buy a wifi enabled chrono on Aliexpress for less than $50, much cheaper than a new gun or an emergency room visit.
Before anything else, I browse the web to find max velocity measurements for the same gun and barrel length.
Then I chrono factory loads with the same bullet weight. This helps me decide on a target velocity.
I've had powder manufacturer published loads create significant over pressures in the past. I don't trust them.
Especially using Vectan SP3, which is a ball powder in the vicinity of 2400. I have experienced over-flattened primers in a Coonan 357 and stuck cases in a Colt Trooper. Fortunately both of these guns are pretty strong and nothing happened, but it was below published maximums. I am not sure if this a common problem with ball powders, but I have read reports of two bulged MR73 revolver cylinders using SP2, another ball powder, and that is pretty hard to do! That was reported as being within published loads. I never had problems with other powders.
I start with minimum published loads and inch my way forward.
Approaching max loads I weigh each charge. I do use primer signs but only comparing them to the way they look at minimum.
When I reach my target velocity I stop, sometimes before if signs appear.
Without a chrono, you're in the dark...
I think it is a fairly safe way to proceed, but to each his own...
Gil.

[William Yanda]

"You can buy a wifi enabled chrono on Aliexpress for less than $50, " gilgsn

Thanks for posting. I have contemplated calculating velocity from trajectory data, this sounds simpler and financially doable.

[fayettefatts]

I would like to read a review of this chronograph from an owner.

[BoBSavage]

It seems to me that a primer will flatten at the same pressures using this theory, of simply checking for flattened primers to indicate excessive pressures. Is a Winchester small rifle primer not the same for all rifles cartridge, regardless of pressures used? Why would the primer flatten for one cartridge application at a particular pressures, but not flatten in another at the same pressure?

[deces]

It seems to me that a primer will flatten at the same pressures using this theory, of simply checking for flattened primers to indicate excessive pressures. Is a Winchester small rifle primer not the same for all rifles cartridge, regardless of pressures used? Why would the primer flatten for one cartridge application at a particular pressures, but not flatten in another at the same pressure?

Not sure about Winchester, but CCI makes at least 3 different SRPs standard SRP, Benchmark SRP and Military SRP. Those military primers are harder and less likely to show deformations.

[Gobeyond]

I had fun compressing grains of Varget into a 223 case which was the max load. I had flattened primers and no other signs and it was accurate in my strong bull barrel. Hey it was the max load, ok. But in 45 colt with of Hs-6 I had no flattening of primers but other signs: bulged cases, carbon, more recoil. So I know not to shoot that in conversion bp pistol anymore. It said only 13000 psi. It’s on them. They give safe info in reload books. Modern Guns should be able to handle the data.

[Good Cheer]

My solution to sneaking up on max is to have the cast boolit (and its accuracy) to be the weakest part of the system being tested.

[Harter66]

I have and have had exactly 2 of probably 70-80 arms that shot their best groups at max loads . The XD40 shot the same feed and eject with closing 25 yd groups all the way to the max load for a 175 jacket under a Lee 401-175 w/o any real changes other than a slight visual closure of the primer shoulder radius . I don't know if I should really count the BlackHawk in 45 Colts or not but even 10% over maximum with 250-265 cast neither cases or primers did anything to display pressure. Even running that hot the Ruger wasn't breathing hard and the loads were probably all of 20-21kpsi so there's no reason why they would show anything at all .

In rifles I had an 06' that shot it's best groups right at start loads making 2700 fps MV when I first started working it and pushed on up looking for the groups to close again ....... didn't happen I also never had any pressure indications although with a 150 probably close to 3100 fps MV it's unlikely that I was anywhere under the 58 kpsi more likely closer to 65 kpsi . No need to revisit that .

I had a brand new 7×6.8 SPC built without actual data I reasonably concluded that anything you could shoot safely in the parent 6.8SPC would be completely safe with the extra .007 dia to soak up the pressures even with a 1-8.5 vs 1-10 or 1-11" twist . Further a paper patched cast should further reduce pressure and it was throated the same as a 7-30 Waters ...... So loading a 27-130 FP paper patched to .285 , I learned several valuable things. 1st that I should always weigh my alloy from a new to me mould and never assume that it won't be more than 2% heavy just because that's what the last 15 dropped ....that 141 gr bullet didn't help matters . 2nd that just be cause a load tracks perfectly with load data for velocity track doesn't mean that's whats actually happening . 3rd a Terni 41' 91 Carcano handles gas , primer debris, and case head "mist" very well . Even those , yes I fired 2 , didn't have more than a slight increase in bolt friction and slipped free of the chamber without any indication of head separation.......well aside from the RP lrp pocket being about .220 dia . My best guess is that that last load a full 1.5 gr below the 130 jacketed max load was in the neighborhood of 75kpsi . It and the .3 lower load that didn't vent or even stretch pockets clocked that 140 just over 2400 fps MV which puts a 7-30 Waters shaped case at 223 length at 7×57 start loads .......and probably well into the 60+ kpsi . The rifle is fine , I'm good to go , no harm done. No pressure signs prior to the primer and pocket failure.

I've become fond of pointing out that there is a reason why pressure limits are set and that the "lawyer data" really isn't all that different from the pre-sue happy era .

I did have a Blue Dot 357 event . Standard data start loads from new , well new then , Hornady data for the 140 XTP . The start load stuck the first 6 cases tight . Like brass rod w/ 4 oz ball peen tight . In hindsight that particular Taurus probably had a 9mm groove and .356 throats . I hadn't yet had the cast bullet enlightenment at that time . I don't remember the primers being especially flat but I do remember that I had to use tools to get the first half of every one of the 6 cases out and the last half was still gravely and unpleasant.