Pressure signs.

[Shadow9mm]

Just found MarkandSam after work put out a video on pressure signs.
https://www.youtube.com/watch?v=dVYSG8VO9EU

I know I have seen some discussions in the past that stated pressure signs are not a valid way to check for pressure. I feel that there are some caveats like brand, lots, and the like. However given the same primers, used in the same cartridge and same firearm during testing I have found it to be a useful tool make sure I am not getting up too far in the pressures.

I hope this wont go as poorly as a 9mm vs 45acp debate.... But given the proper circumstances I have never really understood why one should not take into consideration the state of the primer, and why some other pressure signs like extractor marks seem to be considered more credible.

Thoughts?

 

[44 AMP]

Consider this,

When you hear people say " pressure signs are not a valid way to check for pressure." you are hearing only half the truth.

When they say " pressure signs are not a valid way to check for pressure." and stop there, what they are leaving out is "they do not reliably tell you what the pressure is."

Now, consider this,
DOES IT MATTER???

And what I mean by this is, does it really matter what the actual pressure value is? in psi, cup, or what ever units are used?

What primer signs and all the other pressure signs are telling you is that something has changed from "normal". They can't tell you that your load that you expect to be 35Kpsi is actually 37Kpsi, or 43Kpsi, only that there is something different, and its probably higher than expected pressure.

Different enough to leave marks that usually aren't there. When that happens its time to stop and figure out why. And to be aware that what you're looking at is unique to your gun and the specific combination of components you are using.

Different guns can, and do react differently to the same amount of pressure, and what may be fine in one could be too hot in another, and still be within the "safe" published loads in the manuals.

Just as different guns can give different velocities they can also react differently to the pressures involved.

As an illustrative example, some years ago I loaded some pretty hot 125gr .357 Mag ammo. It was a load out of the Speer manual of the day, a bit under their listed max, and according to the book should have been in the 1500fps range from a 6" barrel.

Along with a friend who supplied a 6" S&W M19 and a Marlin 1894 carbine, I supplied a 6" S&W M28, and a 6" Desert Eagle. And a Chrony...

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...)

Chrony said 1620fps and we decided to stop using the M19 at that point. Unfired rounds fell out, but the two fired cases, were stuck. Primers were a bit flattened, but not extremely so, but the cases were stuck in the cylinder and could not be ejected by hand pressure, having to be driven out with a rod and small hammer.

I then shot that ammo from my M28. Very stout. 6 rnds avg mv 1670fps. and cases ejected with hand pressure. primers looked like the ones fired from the M19. Slightly flattened. No other signs of excess pressure.

Fired the same ammo from the Desert Eagle, 9 rnds (full mag), MV avg was 1720fps. Function was flawless. Primers looked just like the ones from the other guns, and no other pressure signs on the cases.

Fired from the Marlin carbine, the results were the same, except MV from the carbine was 2200fps.

4 guns, shooting the same ammo, differnt MV with the 3 with the same nominal barrel length, but different effects on the cases in one of them.

At a later time, I fired some of the same ammo from my Contender (no chrony) and while the case extracted normally when the action was opened, I couldn't pull it out with my fingers.

SO, here we have an example of a load in the books, which, while safe (nothing blew up, or out) was too hot for a couple of the guns that fired it, but not for the others.

What I'm trying to get across here is that, my gun, or your gun, with our individual combinations of components, will do what ever they do, and that is what matters more than any arbitrary pressure limit expressed as a psi number.

Some guns & ammo combinations will show various pressure signs when the pressure is well below standard max working limits. Other guns won't show signs until well beyond the max working limits and possibly not until you're past working limits and into the actual safety boundary area.

Pressure signs won't tell you what you've got, but GETTING them tells you something isn't quite right with the load and gun you're shooting.

I am NOT advocating exceeding any published pressure limits. Just giving some points to ponder, for discussion.

 

[higgite]

What I’ve always heard is that while flattened primers can be a good indication of overpressure in rifle cartridges, it is not a good barometer of overpressure for pistol cartridges because by the time you get pressures that will flatten a pistol primer, you’re already into rifle pressures and well beyond max pistol pressures and you may notice shrapnel before you notice flattened primers.

 

[Shadow9mm]

What I’ve always heard is that while flattened primers can be a good indication of overpressure in rifle cartridges, it is not a good barometer of overpressure for pistol cartridges because by the time you get pressures that will flatten a pistol primer, you’re already into rifle pressures and well beyond max pistol pressures and you may notice shrapnel before you notice flattened primers.

In my experience that is not necessarily true. Pistol primers generally have thinner cups and will flatten easier than rifle primers. This is due to the lighter striking force of pistol firing pins. However when using magnum or small rifle primers, except in my 357 loads, i do not see flattening on those primers.

 

[Jim Watson]

Right, I once frightened myself by loading some below maximum 9mm with the Federal primers I keep for my revolvers. Scary. Back to WW, normal appearance.

The old old Speer guideline was to increase until you saw ONE "pressure sign" and then reduce by 6%.

Nowadays the Intrepid Internet Loader increases until he gets hard bolt lift, and cratered primers, and ejector wipe, then "backs off half a grain."

 

[Shadow9mm]

Interestingly with 223 in my ar, i get ejector swipes before i get cratered primers. Generally they are all lightly flattened.

 

[zeke]

Reading pressure signs to justify exceeding listed proven load data, or velocities, is very ill advised imo.

However, it is possible that the pressure signs are good indication of increasing pressures in an incremental load work up. Just not that you are still at safe pressure. And depending on what pressure sign you are referring to, some "pressure signs" are certainly indicative of over pressure in a specific firearm

 

[gwpercle]

1.) The first thing I look for is " Sticky" extraction of fired brass .
2.) When extraction becomes hard ... stop... somethings up .
3.) When the primers won't stay in the primer pockets but keep falling out of your reloads ...
you might need need to drop back on that load ... or use another powder or get a new loading manual ...
...Speer Reloading Manual #8 needs to be replaced .
Gary

 

[mkl]

...Speer Reloading Manual #8 needs to be replaced .

I always thought of that manual as the "Speer Manual of PROOF Loads"

 

[GeauxTide]

44AMP's response is to be carefully considered. In my 52 years of loading and chrono graphing, there are almost infinite variables in components, including firearms. I've had several 7mmRM, 308, and 30-06 rifles and not all would digest the same load to the same accuracy or chrono results. My experience with Remington primers is they are softer than Federal, Winchester, or CCI, for instance. When I was "hot rodding" in my younger days, I would go to the point of extractor marks on rifle and hard extraction on pistol. With the increase in bullet technology, I stay at least a grain or two off book maximum.

 

[gwpercle]

I always thought of that manual as the "Speer Manual of PROOF Loads"

LIKE !

I started reloading in 1967 ... bought the 1970 Speer #8 thinking I was getting the newest most up to date manual ... I thought Speer knew what they were doing ...
used data out of that book for 25 years ! I didn't know ... wasn't no computer or reloading sites to get info !!!
Thank Goodness for sites like this .
Gary

 

[44 AMP]

I always thought of that manual as the "Speer Manual of PROOF Loads"

And the Hornady manual is the manual of wimp loads...

And the Lyman is somewhere else, I suppose...

For some rounds (.357 Mag, I checked) the Speer data is the same in #8, 9, & 10.

Point here is that each manual tells you what gun they tested the loads in, and are GUIDELINES because you and I don't have the gun they used for testing. Even if its the same make, model, and features as their test gun, it can be different enough to give noticeably different results.

It's reasonable to expect similar results from a similar gun, but one must always be aware that even a similar gun can give significantly different results.

Guidelines, not rules....arrrrh!!

 

[reddog81]

If pressure signs show up they are something you should pay attention to. The problem with many cartridges is that no pressure signs will show up anywhere near the normal operating pressure of the cartridge.

Additionally many people aren't really sure what a flattened primer looks like. They'll look at a normal .38 Special primer and see that it has a flat section and for some reason assume it must be over pressure. Nope, the rear of the primer is normally flat... Once the rounded edges of the primer start to disappear that might be pressure sign. Once the rounded edges are completely gone you're probably well over pressure

Ejector marks on brass and hard to eject brass is definitely something to pay attention to

 

[9MMand223only]

u can definitely measure components to understand pressure. You just have to use a lot quantity enough to eliminate spikes or anomalies due to inconsistencies in the materials.
On left is primer, right is brass size. the 1.745N is (normal). If you put both together, you can see clear trend. Especially if you measure vs a control, like this.

the last one was not intended for this power factor and is terrible choice. The pressure sign measurements of both the brass and the primer are consistent with this theory of choice.

 

[44 AMP]

The problem with trying to equate various degrees of pressure signs with a specific amount of pressure (psi) is the potential difference between what ever you're looking at for a basis, and everyone else's components.

Even different lots of the "same" components can have different enough characteristics to show different results.

take for example, ejector marks on the brass. Different lots of brass might show marks at different pressure levels, as some is "softer" than others.

Ammo that shows the mark in gun A might not in gun B, and so on.

or cratered primers for another example. Had a pretty warm load I used in my Sig 220, everything normal looking about the fired brass, though muzzle blast and ejection were more...energetic than usual.

same ammo fired from a friend's pin gun. Compensated 1911A1. Gun ran fine. Every primer was cratered.

Again, same ammo, so same pressure (right?) but different results in different guns.

 

[Scorch]

One thing I haven't seen anyone mention is that by the time you see signs of excessive pressure, the round has already been fired in your gun so the damage is done.

As far as reading pressure signs to fine-tune loads, you must have super eyes because I can never tell the pressure by looking at brass, only that the pressure is too high. What we call pressure signs are really signs of excessive pressure. Brass from normal pressure loads look normal, then we try to play around with the high-pressure Ouija board to see if we think it's too high.

 

[reynolds357]

Just found MarkandSam after work put out a video on pressure signs.
https://www.youtube.com/watch?v=dVYSG8VO9EU

I know I have seen some discussions in the past that stated pressure signs are not a valid way to check for pressure. I feel that there are some caveats like brand, lots, and the like. However given the same primers, used in the same cartridge and same firearm during testing I have found it to be a useful tool make sure I am not getting up too far in the pressures.

I hope this wont go as poorly as a 9mm vs 45acp debate.... But given the proper circumstances I have never really understood why one should not take into consideration the state of the primer, and why some other pressure signs like extractor marks seem to be considered more credible.

Thoughts?

This is an example of why primers readings can be worthless. .30-30 Winchester, lever action.

 

[44 AMP]

One thing I haven't seen anyone mention is that by the time you see signs of excessive pressure, the round has already been fired in your gun so the damage is done.

IF there is actually damage...

Which is the feeling I get from reading a lot of posts, that many people expect or believe that slightly exceeding the working pressure standards will damage their firearm.

This has not been my experience. My personal experience over 50+ years of shooting and reloading is that the common pressure signs, seriously flattened primers, cratered primers, ejector marks on the brass, even sticky extraction happens before you are into the range of pressure that will damage a firearm that is in proper working condition to begin with.

They are telling you something is wrong, and you aren't where you should be, but they show up well below actual danger pressures.

After all, firearms survive proof test loads without damage....

Now, bear in mind, I'm talking about signs that show up when you are working up a load, increasing in small steps. IF you just choose a heavy/max load without working up to it in your gun, you COULD get high enough pressure to do damage, right out of the gate, and of course, if you do, you WILL also have pressure signs on the brass because of it.

SO, yes, a load that is dangerously overpressure will show serious pressure signs, but pressure signs often and usually show up before you reach that point.

Think of them kind of like the rumble strips on the edge of some roads. Tells you something isn't right, not good place to run, and warns you that if you keep going in that direction, you WILL run off the road, at speed, and that WILL do damage to the car, and perhaps to you as well.

 

[HiBC]

I take a comprehensive "in total" read of every feedback I can sense. Its like tracking,or weather. What story is being told?

A sign can be misleading. I've seen very flattened primers resulting from excessive head clearance at moderate pressure.

I'll tell you of a "pressure sign" that may be significant to most of us in these days of shortage and high price.

For sure 223/5.56 brass, and maybe 308 family, is susceptible to enlarged primer pockets. Its your brass,do as you want. You may find the price of that extra 89 fps is 1000 pcs of 223 brass ,loaded to near max is 1000 pcs of loose primer pockets.

Premature scrapping of a large lot of brass is a sad thing. It can,and does happen before fear of blowing up the gun shows up.

A slight moderation of load can save your brass and make your barrel last a little longer. The economics of pushing the edges are worth considering.

I do accept "pressure signs" as a warning. A red or yellow flag. A "heads up! Something is going on!!

I do NOT use them as a measuring tool, or an indication I can "bump it up a little more"

I do not recommend "Yeah,thats book max, but I"M SPECIAL cuz I CAN READ PRESSURE SIGNS."

Thats narcissistic delusion.

 

[Rimfire5]

44 AMP in post #2 is on to something.

Think about it. When a particular barrel or chamber is reamed, it is one of many in a string of barrels or chambers being reamed. The reamer is used over and over again until it is declared worn and discarded.

The first barrel and the last barrel reamed by a particular reamer will be entirely different.
The last one will have a tighter bore or chamber than the first one.
Tight chambers cause higher pressure.

Case in point:
I bought a new Savage 6.5mm Creedmoor 12 LRP bolt action rifle several years ago that shot incredibly accurately.
From the first round, it showed serious high-pressure signs with both factory ammo and then with hand loads loaded about 9,000 psi under Pmax (based upon QuickLOAD's predictions).

I dropped the factory loads by about another 8,000 psi and the high-pressure signs were still present.
Finally, I reduced the loads another 8,000 psi and still got high-pressure signs.
I was just about at the minimum load recommended.

I had taken pictures of the brass and load data at each load level showing the flattened primers and the flattened head stamps on the brass and sent them to Savage.
They immediately sent me a label to return the rifle to the factory.
About 2 weeks later I got the rifle back with a note that they bored out the chamber by a few thousandths.

The corrected chamber shot with the same accuracy but never showed a high-pressure sign again, regardless of the load level.

I concluded that the reamer used on the chamber was probably at the end of its useful life before they bored out my original chamber. Getting the chamber back to spec reduced the high-pressure signs.

As 44 AMP pointed out, individual chambers can react differently with the same ammo.