Pressure signs and what they mean

[6bg6ga]

Recently reloaded some 40 cal in 180gr SWC with 5.2 gr or WW231 which is well in the safe zone. OAL case length was to fit the chamber of the Glock 35 I was loading for. The plunk test showed I was spot on length wise. Shooting them revealed these was pressure excess pressure in my opinion based on what father taught me 55+ years ago. A flattened primer means its hot but when the primer starts coming back on the firing pin look out. That my first experience with the excess pressure of this type.

People were shooting 9mm's and I examined their factory loaded brass and found the same thing. So what gives? Was Papa wrong? Everything I have been taught was an error?

[6bg6ga]

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[kingrj]

Sometimes an oversized firing pin hole in the slide can cause primers to give this appearance and in combination with firing pin drag from a too weak firing pin spring can also do this..With out pressure testing equipment the next best thing is a chronograph. If the load chronographs at or less than what the loading manual suggests for this load you are likely ok. If pressures are too high then the velocity will be much higher than listed. I know this is going to sound kinda stupid but I am going to ask anyway...so do factory loaded rounds make the primers look the same way? If so you probably don't have a problem..

[17nut]

Glocks has that odd square firing pin hole wich ends up as a raised spot on the primer.
They all do it and it has little to do with high pressures, well yes it has to do with high pressure but not excessive pressure.
It's a quirk in the guns of the camping gods maker, that and the water pistol trigger!

[35remington]

Daddy nor yourself knew anything about Glocks or pistol primer behavior. Now you do. And yeah, "interpreting" what you see on primers requires context. Otherwise it is bad information subject to misunderstanding.

As here.

[tazman]

Coming to pistol reloading from rifle reloading, I had the same thoughts for a time until I found out that handguns are a different beast. Even with higher pressured handgun cartridges(9mm, 357, etc) the pressure signs aren't as obvious or even the same as in a rifle. A lot has to do with the differences in the components. Pistol primers are usually much softer than rifle primers and vary more lot to lot. Same for the brass.
Where a rifle firing pin must be fitted closely to avoid the appearance of cratering, often handguns are are fitted loose for reliable ignition and function.
You just have to get used to what your particular pistol does and, as was mentioned before, use a chronograph to verify your results.
If you have access to pressure testing equipment, go for it.

[OS OK]

If you 'tinker' in the upper 'nether regions'...get a Chrony and use it. Primer flatness around the edges varies in pistols and revolvers and it varies from one brand to the next...oversized firing pin holes will do this. When you start to get mirror images of the breech face on the base, that's another indication of high pressure. What does your group size tell you when you shoot off a bag? Do you have the unexplained fliers? With too much pressure everything will start to go sideways...why go there?

Without pressure testing equipment only the Chrony and 'good sense' will keep you out of trouble.

Yo Daddy was spot on!

[Eldon]

Over and over we keep beating this subject ! KISS applies !

If your load exceed the published velocity of a reputable current reloading manual (you need a chronograph !) using EXACTLY the same componets you are, you are on your own.

Don't bore me with "loose bores", "altitude", "phase of moon" etc.. KISS applies and a chronograph is the answer !

[OS OK]

with the amount of chamber variation in handguns, its been told to me that until case heads separate, primers come out of the pocket, or the cylinder wall splits, you have no actual way of figuring out the chamber pressure.

Very true...but, like knowing the seasons without a calendar we have to know the pressure signs, indications that excessive pressure is there or is going to be there if we keep boosting the charge without the pressure testing equipment. You don't need a rocket scientist, just good common sense.

These are from a batch of new plinkers I worked up this past week for the 9. Lee TL-356-124-TC, they're 126 grains PC'd like this and with the soft 11BHN Pb...Loaded with 3.8 grains of Bullseye they have the lowest ES & SD of all the loads tested (3.5 ~ 3.9 grains in .1'th grain incremental batches), @ 1,048 FPS they are not as fast as they could be but they aren't slouchers either, they group the tightest also with no fliers...tested in batches of 10.

This is what the typical primers look like coming from this same batch of plinkers. The one on the left was shot from the Browning High Power and the right one came out of a Beretta 92F...one might say that the primer on the right is starting to show signs of overpressure because of the oversized firing pin hole and the raised area around the dimple. The only way I can be sure that it is not is by relying on my Chronograph...it's all I have and I'd like to think it has saved my bacon more than once especially back in the day when I thought that speed was everything...."taint so!"

[gnostic]

They don't look too hot. Notice, the radius on the primers still there...

[6bg6ga]

Wouldn't the longer barrel keep the pressure longer thus more speed.

[OS OK]

I have never understood how people feel velocity can be used to determine chamber pressure. seriously, look at the load data in your favorite manual. you can see the max charges, and the max chamber pressure and see that the same velocity can be got from multiple powders with different pressures.

Add in how some barrels throw bullets faster then others, and barrel lengths as well. Its not hard to beat the velocity on the box with its 4 inch test barrel data if your using a 6 inch 357. and it miraculously doesn't change the pressure.....

Im not being an *******, just assertive. If a person loads 3 grains of BE under a 148 grain wadcutter, and only manages to get 650 fps from a 2 inch j frame, but can get 700 from his 4 inch k frame,, has the chamber pressure increased somehow to cause the higher velocity?

That's not what we are talking about. We are not measuring, we are talking about 'signs, indications' of overpressure using the limited equipment some of us have available.

[tazman]

I have never understood how people feel velocity can be used to determine chamber pressure. seriously, look at the load data in your favorite manual. you can see the max charges, and the max chamber pressure and see that the same velocity can be got from multiple powders with different pressures.

Add in how some barrels throw bullets faster then others, and barrel lengths as well. Its not hard to beat the velocity on the box with its 4 inch test barrel data if your using a 6 inch 357. and it miraculously doesn't change the pressure.....

Im not being an *******, just assertive. If a person loads 3 grains of BE under a 148 grain wadcutter, and only manages to get 650 fps from a 2 inch j frame, but can get 700 from his 4 inch k frame,, has the chamber pressure increased somehow to cause the higher velocity?

You test factory loads and standard book loads in your handgun over a chronograph and use that data as a reference. Then you start working up your new loads. If you are exceeding those velocities and not using a slower powder, you are probably running a higher pressure.
This way you aren't comparing different barrel lengths or different guns. It still won't tell you what pressures you are running, but serves as an indicator of where you are.
If you have a certain velocity you want to achieve, this method can help get you there safely. If you are simply trying for absolute max velocity, you are on your own without pressure testing equipment.

[OS OK]

Wouldn't the longer barrel keep the pressure longer thus more speed.

That's an interesting discussion to listen to. Longer barrel, more burn time and more gas is created if the appropriate powder is used but the other side of the coin is this...all the time the projectile is accelerating it's creating more volume behind it for the gas to fill and the gas has to keep building pressure to keep accelerating the projectile and doing it in such a short time that it just boggles my mind to contemplate.

[OS OK]

Your up early this morning Taz...

[Eldon]

The INCORRECT info goes ON AND ON. Primers DMS ! Does anyone here READ ? Buy Handloader ? Still believe the earth is flat ? The chrongraph is the best tool (absent a pressure bbl) available. Find me ONE ballistics expert that says primers are the BEST way to measure pressure. (Not your uncle Caleb who believes CNN).

This so SIMPLE, it's amazing people whose ballistic knowledge ended in 1970 think they have the answers.

[OS OK]

Why don't you two boys take over here and bring us all up to speed regarding 'pressure signs'...

The INCORRECT info goes ON AND ON. Primers DMS ! Does anyone here READ ? Buy Handloader ? Still believe the earth is flat ? The chrongraph is the best tool (absent a pressure bbl) available. Find me ONE ballistics expert that says primers are the BEST way to measure pressure. (Not your uncle Caleb who believes CNN).

This so SIMPLE, it's amazing people whose ballistic knowledge ended in 1970 think they have the answers.

^ You give it a shot and see if you can write an intelligent paragraph without insulting anyone...

Perhaps if we were using balloon head brass to load say 357 magnum or 44 magnum or 454 casull, then I could agree that visual signs could be used as a way to say if you were loading those cartridges to "hot and heavy".

But when you consider that brass has lot variations, brand variations, country variations.

Consider that the primer is not a very useful thing visually because if you fire a cartridge and the primer looks like it was flowing around the firing pin in a bad way, you have to consider the following:
1. is it really to much pressure?
2. too soft of primer
3. is firing pin to small for firing pin channel?
4. is firing pin channel face worn out or damaged?

If you wanted to get picky about it, any piece of brass that goes through an unsupported barrel in a semi auto and comes out with that bulge, can be considered as having signs of extremely high chamber pressure.

^ and you...try to keep it on point, we ain't loading baloon head brass with modern powder and expecting it to hold. In fact BH brass hasn't been mentioned at all.
Go ahead and jump in with your friend there and straighten us out...only stick to the topic...'pressure signs', put it in context with 'working up a load', that should make an interesting read.

That oughta keep it on point...

[kingrj]

Damn this is getting interesting!! It seems that everybody is pretty much in agreement but the fights have started! LOL!

[JBinMN]

"Just the facts ma'am, just the facts."




A little levity... I thought it funny anyway.

[OS OK]

Me too . . .

Your telling your age!