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.ph...ure-signs.148/

Then there is KABOOM https://www.thehighroad.org/index.ph...ums/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