Pressure Signs from Your Gun

[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.
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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.