I would like to see a discussion on pressure signs.

[tazman]

I have seen all the basic stuff the manuals have to offer(I own and have read 9 manuals) on pressure signs. I have read on this sight several mentions of different things that give a more subtle indication of pressure either too low or too high. There should be indicators of climbing pressure that come before blown primers and flowing brass cases if only I knew what to look for.
With powder being in short supply these days, being able to recognize these signs would greatly aid in load development using powders where data is limited or nonexistent.

Many of the people on this site have decades of experience in this area. What I am hoping for is a listing of pressure signs ranging from too low to getting too high showing where to look at the case or gun and discussion of tools to help with this(chronographs, etc).
Also suggestions of where to start with a powder that there is no data for would be good.

There is some of this data spread over many different threads here. I think it would be a good thing to gather it into one place.

[44man]

We are in the same boat with half an oar. I have been loading for a good 61 years and still have great fear over untested and measured loads.
There really is no way to tell because every gun will do something different, some exceeding pressure out of this world without any signs and another just blows up with a smaller load.
You will get a million answers for what to look for, some are valid but it seems JUST for the gun shot. Now extreme pressure signs like brass that won't extract or brass flowing into ejection ports, head stamp smeared clean, etc, will be well beyond what you ask and what I want too.
Where to start with a powder not listed anywhere for a caliber? Once you understand that a load too light to start can be as dangerous as an over charge and it can make you think it had to much pressure so you take it lower and ruin something because some powders can NOT be reduced, then you will see how I feel about it. Even hard extraction with a load in one gun might never be seen in another. Flat primers can't be read either.
My two cents says this would be a dangerous list.
I don't even trust a lot of book loads.
We really are kind of on our own.

[zoltarp]

Ok that makes me a lil scared.

[Land Owner]

Just Google "pressure signs" and thereafter Images, where a virtual host of conversations and indicators are lurking for your continued perusal.

[sundog]

44man said, "Flat primers can't be read either."

He is right. Just lately I have been fooling around with two different boolits in 3 different 9mm pissolas. One particular [sane] load in one pissola had what I would refer to as a normal looking after firing primer. Good load. In one of the other pissolas that same load had a very flattened primer. Still normal recoil, report, etc., a safe published load. Primers between the two were entirely different look.

I'll stick with published, or known time tested loads (or reasonably approach sane loads with surplus powder that may not have anything other than 'similar burn rate to xxx in some given caliber'). I've been hand loading and casting since the early 70s, and this is what I am comfortable with.

I think the best way to know for sure at our user level, if one can afford it, is a pressure trace.

[Blammer]

In my opinion there is no REAL way to tell pressures with out a strain gauge.

I use QL to help me ESTIMATE what may happen and if it's safe, but usually cross reference that to a manual or two.

[Shiloh]

I stick to info from reputable published sources. Then I use tried and true reloading methods of working up loads. For something obscure or without current data, The forum is a good place to start. Then, the fellows giving info, will tell what works FOR THEM, and to follow proven tried and true reloading methods and procedures.

Shiloh

[bangerjim]

Here is a start for your list:

http://www.shootersforum.com/handloading-procedures-practices/58763-pressure-signs.html


banger

[tazman]

Perhaps I should clarify my question a bit. I am mostly concerned about pistol powders at this point in time. There is considerable rifle data out there including the possible problems reduced load with certain powders might cause. There is also a lot of light load data available in the mouse fart threads.
Around here standard pistol powders are almost impossible to come by. I have worked up a few loads using shotgun powders that seem to fit the profile for pistol use.
I would feel better having more knowledge of what to look for before I catch a slide in the forehead.

Landowner, I did google the topic and got a lot of links telling me what you can't use to tell pressure. Seems like everybody is afraid to say what they know for fear of a lawsuit. Can't blame them for that. I am not looking for data, just a way to tell if I am near the limit.
Bangerjim, thanks for the link, very informative. I can't help but feel there is more info out there.

[Larry Gibson]

I measure the psi of 23 different cartridges in 30 different barrels using a strain gauge and an Oehler M43 PBL. I have been doing so for 6 years now. There is no reliable single indicator/sign of psi as mentioned in many manuals and writings short of actually measuring it. I have been constantly amazed how some cartridges have very high psi with no apparent physical sign of it. This applies to handgun cartridges and rifle cartridges. For example I'll use two longtime favorite hunting loads of mine; one an '06 and the other a 357 magnum. The '06 was loaded with a 180 gr j bullet over a slow burning powder. Velocity was 2750 fps out of the 24" barrel. With W-W cases and WLR primers there was no indication of high psi. I used that load for a number of years on deer, elk, caribou and a nice Big Horn sheep with out a single problem or indication of a problem. When pressure tested the load tested out at 66,400 psi(M43) average with a peak psi at 69,100! The 357 was loaded with a 125 gr JHP over a slow burning powder also. It was a max listed load out of an older manual. When pressure tested it ran at 42,200 psi(M43) with a peak psi at 43,900! Keep in mind the SAAMI MAP for the '06 is 60,000 psi(transducer). The SAAMI MAP for the .357 Magnum is 35,000 psi(transducer). Yes both firearms had "reference" ammunition tested in them to ensure reliability. Neither cartridge exhibited any indication of excessive psi. I could cite numerous examples of such.

My advice to those who work up loads is;

Use several current & reputable reloading manuals as sources for "start" & "maximum" loads. Compare the barrel length used in the manual to the one you are using. Do not expect to equal or exceed the published velocity if the barrel you are using is shorter or even of equal length.

Always, and I mean always, start at the start load and work up. You may very well find a maximum load for your rifle before reaching the manual's listed maximum load.

Become very familiar with all of the "pressure signs" listed in the manuals. If one appears in one of your test loads there is a reason for it. It may not be high psi but there is a reason so don't arbitrarily disregard any high psi sign. If one appears then correlate it with the next advise.

Use a chronograph. They are common enough and inexpensive enough (considering the cost of the firearm, scope, a finger or two or even an eye) that not using one if you are really wanting top end loads is a poor excuse. Pay attention to the velocity. It takes pressure to get velocity; the higher the velocity with a give powder/bullet the higher the pressure. It is that simple. If you are approaching the manual's maximum listed velocity for the powder used but have not reached the maximum powder charge listed then do not assume the pressure is still safe. Remember; it takes pressure to achieve velocity. We always hear of "fast barrels" but they are actually very rare. If your velocity is about equal to the manuals and you have a shorter or equal barrel length you can bet the psi'd are up there with the manuals. Do not be surprised if your loads do not equal the manuals loads in velocity and do not think you can safely.

Again; use several current manuals for reference, consider your firearm as compared to the manual's test firearms, pay attention to all potential pressure signs, do not ignore any pressure sign and use a chronograph for comparisons of velocity of your loads to the manuals.

Be safe

Larry Gibson

[Larry Gibson]

tazman

Perhaps a bit of specifics on the cartridge, firearm, powder(s) and bullets you are wanting to use would be helpful?

Larry Gibson

[KYCaster]

Multiple RELIABLE data sources and a chronograph. (Lee is not a reliable data source)

If ANYTHING doesn't look right; for instance, if data from different sources doesn't agree or you get unexpected chronograph results, STOP and figure out why before you proceed.

If you can't find data for the powder you've chosen, call the powder manufacturer and ask for guidance. There may be a very good reason that particular powder isn't suitable for your particular application.

If you insist on developing your own data in uncharted territory, please do it at your own private range where you don't endanger anyone else.

Jerry

[detox]

Measuring for excessive case head expansion is a good indicator. Sticking bolt (bolt action only) or sticking cases is a sure sign of TOO HIGH pressure.

[dragon813gt]

Multiple RELIABLE data sources and a chronograph. (Lee is not a reliable data source)

Lee does not develop any loads. They simply reprint the loads from the powder and bullet manufacturers. Are you saying the powder and bullet manufacturers are not to be trusted?

[tazman]

tazman

Perhaps a bit of specifics on the cartridge, firearm, powder(s) and bullets you are wanting to use would be helpful?

Larry Gibson
Thanks for both your posts. I was hoping there could be some visual cues but if there aren't any, then I have to live with that.

I wanted to keep this general rather than about any specific cartridge. The one in particular that I am dealing with currently has a reputation for being troublesome. I have worked up a couple of loads that appear to give good results but was hoping for a way to confirm beyond how they shoot and feel.
My next step is now to purchase a chronograph and see what I am getting for velocity. I do not care at all about high speed. Only consistent function and accuracy.
I have been working with a couple of powders in between red dot and AA7 on the burn rate chart and am getting some good results. I wanted to verify their safety if I could beyond shooting a few hundred rounds and the gun not blowing up.
The powder manufacturer told me they didn't have any reason to work up data for the powders in question as they already had those ranges covered with standard pistol powders. The fact that the standard powders are unavailable is of no consideration to them.

I already ran into the too hot load scenario using data published by the manufacturer. Good thing I started low. I got halfway from the start load to the max load when thing started to show problems.
I only had a small amount of that powder borrowed from a friend and it just didn't work right for me.

[KYCaster]

Lee does not develop any loads. They simply reprint the loads from the powder and bullet manufacturers. Are you saying the powder and bullet manufacturers are not to be trusted?


No, I'm saying that Lee has made some serious mistakes when transcribing numbers.

Jerry

[chboats]

Where I have a lot of concern over high pressures is in cartridges like 45ACP and 38 special. The case may never stick, the primer will probably never flatten (from pressure) but you may be exceeding max for the gun. The books say work up slow and watch for signs of high pressure, what signs?

Carl

[bearcove]

Primer flattening is NOT a readable pressure sign. Usually a headspace issue.

A straight wall case may not stick till you are WAY over pressure. My 454 at MAX loads 60,000 +psi and the cases fall out. Are you going to use that as a pressure sign for 45 colt?

Primer flowing or printing of the breach texture on the primer is a HIGH pressure sign.

Anyone who loads by looking for pressure signs is a fool. That's why we have manuals. They test pressure. Yeah you can exceed that pressure but usually with little to gain and alot to lose.

[bearcove]

Measuring for excessive case head expansion is a good indicator. Sticking bolt (bolt action only) or sticking cases is a sure sign of TOO HIGH pressure.

Case head expansion is what Ken Waters used. Need a "known" factory load to set a standard case head expansion measurement for your rifle. Then you need the book "Pet Loads " so you can read the rest of the method.

[Gtek]

The sticks and stones one does not seem to not be real anymore. What about the one that starts with people that play with fire? Gtek

[MtGun44]

The only way without strain gages or peizo transducers is to match your
velocities with the book. If you are a bunch faster, you have higher pressure
ALL THINGS BEING EQUAL - which they generally are not. If you
are careful to compare apples to apples as best you can, velocity is pretty
useful. All else is nearly useless, other than if you have a sticking bolt
or something you are probably WAY, WAY over.

The only way case head expansion is accurate is with identical brass. Not a
chance of that with factory ammo compared to reloads. "In the general
ballpark"? yes, "Accurate" - no.

Bill

[44man]

Good going for some of you. I respect Larry for his work so don't ignore it.
This is something not to be guessed at.
Gtek, we do play with fire. It is to know how much flame.

[mdi]

http://www.shootersforum.com/handloading-procedures-practices/58763-pressure-signs.html I ran across this discussion on a forum a while back...

[243winxb]

Photo albums with some pressure sign at this link. http://www.photobucket.com/kabooom http://i338.photobucket.com/albums/n420/joe1944usa/EjectorMark_01.jpg http://i338.photobucket.com/albums/n420/joe1944usa/FirearmsReloading102/PressureSigns.jpg

[44man]

Photo albums with some pressure sign at this link. http://www.photobucket.com/kabooom http://i338.photobucket.com/albums/n420/joe1944usa/EjectorMark_01.jpg http://i338.photobucket.com/albums/n420/joe1944usa/FirearmsReloading102/PressureSigns.jpg
Very good post but places I don't want to get near. Wonderful pictures.
Still, what to do with a powder with no book loads? The OP had a valid question that I cant answer and am scared to death to say anything.
The huge primer pocket blown out might be a be an S.E.E event with a low load. Yes, I am going to say that, not a normal high pressure load.
Not one single primer pocket blown that large has ever been from just pressure. It is a S.E.E event.

[fecmech]

Where I have a lot of concern over high pressures is in cartridges like 45ACP and 38 special. The case may never stick, the primer will probably never flatten (from pressure) but you may be exceeding max for the gun. The books say work up slow and watch for signs of high pressure, what signs?
IMO there are no signs for any of the low pressure cartridges like the .38spl,.44spl,45acp. The book statement is simply CYA.

PS. About your only indication would be a high velocity in comparison to book values over your chronograph.

[DeanWinchester]

I could be wrong, usually am, but I refuse to go by "signs" for loading. A short time ago I had a .300 blackout built on a Savage 110. I was running Lil'Gun and YES THIS WAS FOOLISH but I was running WAY more than max listed. I felt the Savage action would be VERY difficult to compromise so I pushed. I didn't get into trouble, but I was running around 20.0g. Max is around 17.0 if I remember right. At 19.0g I had NO signs. Even the primer still had a radius. the primer was flat at 19.5. At 20.0g I was getting case flow and ruining brass.
Every time for each load, I had smooth extraction, easy bolt lift. Up until I was around 19.0g I wasn't even having to trim brass.

This was incredibly dumb. What if I had been doing this with a action/cartridge combo that wasn't as tolerant? Trying to judge by the signs you divine from brass is just not safe.

[tazman]

44man wrote:Very good post but places I don't want to get near. Wonderful pictures.
Still, what to do with a powder with no book loads? The OP had a valid question that I cant answer and am scared to death to say anything.

I can certainly appreciate your position. In this situation everyone is afraid to say anything for fear of being misunderstood or being liable for some one else's mistake. I probably would be too if I was on the other end of this question. I can't blame anyone for being hesitant to give advice here.
I also respect Larry's posts as he always gives a considered response and his knowledge far exceeds mine. I wish I had some of his resources.
I certainly appreciate your responses and realize you are being as helpful as you can.
Thanks a bunch

[leftiye]

Where I have a lot of concern over high pressures is in cartridges like 45ACP and 38 special. The case may never stick, the primer will probably never flatten (from pressure) but you may be exceeding max for the gun. The books say work up slow and watch for signs of high pressure, what signs? Carl

This is a good place to start in as to pressure signs. You're right, these shouldn't show pressure signs, but they do expand the case to approximate the chamber. The 21,000 psi of the .45 acp is actually very much in the realm of pressure being plenty to expand a case right to the edge of "pressure signs." As for other cartridges, as has been said reduced loads found in literature GIVING PRESSURES GENERATED is where to start. This data WON'T BE ACCURATE in your gun. That's why you start with reduced loads. This gives you a place to start observing signs in higher intensity cartridges.

BTW, unless you're dealing with a very old, weak gun (the weak ones are all old), you probly can't damage a gun before seeing some pressure signs (particularly scuffing), though it would be better to mike case heads and stop when you get a sharper expansion ring (not to be confused with case head expansion) than to see scuffing. Flexing of chambers being what it is, you'll see scuffing before there is any danger of damage to the gun, and/or kaboom. You'll see sticking in a gun before there's a probabilty of damage or rupture, time to reduce loads (note possible exception as per Dean Winchester's post. Probly something about fast powder ran at rifle pressures). So, pressure signs aren't even necessary to keep thumbs and eyeballs where you want them to stay. The good news is that pressure signs obviate the need to rely on (should I say take a chance on?) these parameters such the as sticking/ flexing progression.

Back to .38 special pressures. These low pressures will let you know how big your chamber(s) is/are (approximately). BTW we're NOT talking about case head expansion. That only comes with pressures above 60,000 psi when the plastic limits of the brass are exceeded, and brass flowing has begun or is about to begin. We're talking about measuring the pressure ring in front of the case head. Most of your useable loads are about .001"larger than these low pressure loads. Then when scuffing appears you're approaching max pressures (all rifle loads in the vicinity of maximum will show some scuffing, so will all magnum revolver loads and most auto pistol loads). When scuffing becomes bright or intense, stop adding powder! When that pressure ring expands another half thou. from the starting measurement (low pressure plus .001"), you've arrived at all that gun wants to survive, back off a bit. When your case heads expand, throw the cases away. When the brass flows, say a prayer of thanks. But there IS a progression of "pressure signs" that, if payed attention to, will help make it possible to survive our hobby. Notice I didn't say anything about pressure detecting or measurement (pay attention). It's actually about gun prediction.

[44man]

Long ago when MR was working on the Lone Eagle, they tested to destruction but only got it once. They never damaged a single gun until they got so hot a load the brass melted and brazed itself to the chamber walls. The gun still did not break but was ruined. It had to be cut open to see what happened.
Might I say when the brass melts, you might want to back down! [smilie=1:

[Larry Gibson]

Photo albums with some pressure sign at this link. http://www.photobucket.com/kabooom http://i338.photobucket.com/albums/n420/joe1944usa/EjectorMark_01.jpg http://i338.photobucket.com/albums/n420/joe1944usa/FirearmsReloading102/PressureSigns.jpg

Problem with all of those pressure signs is that by the time you observe them the loads are way over even the highest acceptable psi for that cartridge, the MPSM (Maximum Probable Sample Mean), let alone the MAP, (Maximum Average Pressure) for that cartridge. Those loads probably are at the level of "proof loads" or above that level. While developing loads until you get any of the above pressure signs might be a questionable "safe" course in a modern bolt or SS action one certainly would not want to take loads to those levels in most handguns or older rifles.

Let me reiterate one point I made earlier; use a chronograph. No, the chronograph won't tell you pressure and I'm not telling you it is. However, if your loads are approaching published velocities from reliable sources with similar components using the same powder out of a similar length barrel then you can bet you are approaching, are at, or are even over the same psi level of the referenced load within normal psi variance +/- . Most all reliable manuals that are current keep loads within SAAMI spec for that cartridge. I know there are some exceptions but if using a cartridge in the "exception" category then make sure the firearm used is correct for the loads. (i.e. don't use Ruger/Mauser level 45-70 data in a Trapdoor).

Larry Gibson

[Outpost75]

One of the best general statements on pressure related to cast bullet loads what I have read, came from Col. E.H. Harrison, USA (Ret.) in the NRA book "Cast Bullets,"

Col. Harrison's advice was that "Accurate cast bullet loads are safe...." and I have found this to be true in the last 50 years I have used them.

[243winxb]

The red circle (above) is around where the brass has flowed into the ejector hole. This same mark may be seen on some, not all, factory rifle ammo. The one on the right being the worst for factory. On pistol cartridges, the case takes on a "spider web" effect. I feel this is because the brass does not spring back its normal amount. Very had to get a photo of it, but can be seen even in the 45 acp. The 45acp may bulge first, if unsupported. The conditon of the chamber may have an effect also. http://i338.photobucket.com/albums/n420/joe1944usa/Firearms%20%20and%20%20Reloading/44MagPressureA.jpg This 44 mag. brass has been marked by the chamber. Not the spider web effect. Many rifle & handgun cartridges run at 65,000 PSI.
modulus of elasticity- Cartridge Brass-
Material is 70 copper/30 zinc with trace amounts of lead & iron , called C26000. Material starts to yield at 15,000 PSI when soft (annealed), and 63,000 PSI when hard.
Material yields, but continues to get stronger up to 47,000 PSI when soft, and 76,000 PSI
when work hardened. Larry Gibson has the pressure testing equipment, not i. So best to go with what he said. :-) Fast shotgun/pistol powders in large rifle cartridges, using cast boolits, may jump pressures fast when no data is available. Be Safe.

[Bigslug]

As for sorting out where to start for a combination that isn't in the books, calling the powder manufacturer is one option, but more than once I have made an educated guess based on available data for similar rounds being used in similar guns. For example, you might not be able to find data for your 6mm or 6.5mm .30-06 wildcat, but you can start on the low end of .25-06 data and be safely in the ballpark for starters.

For non-autoloaders, when you start clearly branding impressions of the bolt face on the base of the cartridge (lines made by machine marks, the ejector cut, etc...) you know you're running too hot. Flattening primers CAN be a good indication, but thickness of the primer cup can influence that greatly. The CCI military primers are thicker and a lot more resistant to this deformation than a lot of others. The problem with this approach is that while it's fine for a Remington 700, Ruger Blackhawk, or other built-like-a-brick-outhouse modern firearm, relying on it for older, weaker guns may be asking for some grenade action.

For autoloaders with an impact-style ejection system, where is the brass being thrown compared with factory stuff. If you've got a known safe load, match it's ejection pattern.

[Airman Basic]

I can usually tell pressure signs from MY guns that I'm familiar with. I've shot them a bunch and know what to look for with each individual weapon. I don't have so many that I can't remember them all. Sounds like an interesting problem to have, though, don't it. :Fire:

[leftiye]

A good example of the usefulness of being able to look at and measure a case and to know when pressures are too high-. I thoroughly researched a group of loads and published these loads here in a thread called "Moderate 32-20" loads in the "CB Loads, Your Favorite Cartridge" forum.

For one thing, I probly misnamed the thread. (maybe they weren't moderate) The loads were for strong group 2 (Kelley) guns. All of the research said the loads should be in the 16,000 to 20,000 psi range. I started testing them in a Colt Official Police revolver. Every one of them needed to be reduced. Even the standard 10.0 grains of 2400 (Kieth) load was all the poor gun wanted to take, and was a reduction from the data I had found. BTW, Rem. 1 1/2 primers are a good pressure test for this pressure range. They have soft cups and perforated in some of the loads. Backing off until they held was a good test of pressures that didn't show excessive signs. Sometimes the published data lies. Sometimes your gun is outside the norm for building pressure. That gun would get very high velocities with published loads (and would be building higher pressures than the guns used in the manuals).

[William Yanda]

No, I'm saying that Lee has made some serious mistakes when transcribing numbers.

Jerry
If you consider Lee infallible, compare the "useful case capacity" for the 307 Win. to the 308 Win. and the 300 Savage. I believe the 308 was developed from the 300 Savage, and the 307 is a rimmed version of the 308 to skirt regulations that disqualify "military cartridges". At least that's what wiki says. Then compare the dimensions. Except for the rim, 307 appears identical to 308, yet the useful case capacity is listed closer to the 300 Savage, which has smaller dimensions. Go figure.

[243winxb]

As for primers falling out of the pocket. A guy from the next bench comes over to me, asks, why did this happen? The 300 Win. Mag case had the primer missing. He loaded to hot and pocket expanded. Brass loaded the 2nd time with more powder. A new reloader, so he said. Beware of the person next to you at the bench. And if the 338L or 50 has a muzzle break, move. Side spritz from a S&W 500/460 is another reason to move. Beware of flinklocks, almost lost an eye while shooting 10 feet to the guns right side. Flint chip at 1500 fps will do damage to soft tissue. Drew blood on my eyebrow. Shooting glasses should always have side shields.

[JimA]

If you consider Lee infallible, compare the "useful case capacity" for the 307 Win. to the 308 Win. and the 300 Savage. I believe the 308 was developed from the 300 Savage, and the 307 is a rimmed version of the 308 to skirt regulations that disqualify "military cartridges". At least that's what wiki says. Then compare the dimensions. Except for the rim, 307 appears identical to 308, yet the useful case capacity is listed closer to the 300 Savage, which has smaller dimensions. Go figure.

The .307 Win case has thicker walls which reduce the internal capacity. It is equivalent to 7.62 Nato internal dimensions. It is a couple of grains less capacity than .308 Win and a couple more than .300 Sav. This is grains of H2O.

[Harter66]

Let me share a tale of a certain Mark X varmit bbl varmit stocked 22-250.

The temps were in the 90s, we were in full sun, shooting rocks random spots etc.
The load was Win white box 40gr HP. I shot a few to check that the rifle was liking the load an still yote-able to 400ish it was and did. About the 7th round started to show gas leaks around the primer at the 10th the primer dropped out and had aeparated 250+ degrees around the head. Factory ammo here w/escalating to failure pressure. 10 rounds in about 10 minutes in a classic 98 action.
Later w/ much WTH and scratching of both ends I gathered up 20 Win cases and loaded 30.0 of 3031 under a 55gr Win fmj (no where near a top load 32+) and proceded to repeat the expirence 7 leaked 10 dropped the primer. In the end I am left only w/the heat of the day and the action/bbl not being able to shed the heat fast enough............how did Germany fight a war w/the damned things in Africa ?

Please grab your Speer book and re-read why Balistitians get gray...

[DeanWinchester]

Good point Harter.

No pressure signs today, over cast and cool. BIG pressure spike out in the August sun.

[MtGun44]

I think the .307 was made to work in break action guns.

Bill

[JimA]

I think the .307 was made to work in break action guns.

Bill

While it would work great in a break action because of the rim, It was designed for use in a tubular magazine lever action. The Winchester model 94 Angle Eject specifically.